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TX-1 Apache Problem Brand New Member

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  • kj4ws
    I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground.
    Message 1 of 26 , Oct 18, 2013

      I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.

       

      On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.

       

      The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can't see why it wouldn't be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....

                                                                 73 from Wade/KJ4WS

    • bambazonke01
      The bias comes from the 680 ohm on the cathode. If the 0.2 mfd capacitor across it is shorted out then the cathode is at ground potential and the grid turns
      Message 2 of 26 , Oct 18, 2013

        The bias comes from the 680 ohm on the cathode. If the 0.2 mfd capacitor across it is shorted out then the cathode is at ground potential and the grid turns full on with no bias.

        Maybe the 500K level pot on the o/pf the 12 au7 is open circuit so the level is turned full up.

        Going further back along the audio line , maybe the 6AL5 clipper has died and the audio is not limited. Turn down the gain.to see.

        Jim VE3DDY..

         



        ---In heathkit@yahoogroups.com, <tvman1954@...> wrote:

        I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.

         

        On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.

         

        The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can't see why it wouldn't be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....

                                                                   73 from Wade/KJ4WS

      • Howie
        Check the tube socket real good for carbon tracks and good connections to the pin. With 0 bias the tube shouldn`t run away like it does. ... From:
        Message 3 of 26 , Oct 18, 2013
          
          Check the tube socket real good for carbon tracks and good connections to the pin.
           
          With 0 bias the tube shouldn`t run away like it does.
          ----- Original Message -----
          Sent: Friday, October 18, 2013 8:05 PM
          Subject: [Heathkit:Yahoo] TX-1 Apache Problem Brand New Member

           

          I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.

           

          On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.

           

          The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can't see why it wouldn't be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....

                                                                     73 from Wade/KJ4WS

        • k4pf@juno.com
          ... Hi, Welcome to the reflector. I would disconnect the grid capacitor from the previous stage (pin 2). The schematic shows 10V on the cathode, across the 680
          Message 4 of 26 , Oct 18, 2013
            > Wade KJ4WS wrote
            > have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice. <snip>
            >The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly. Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can't see why it wouldn't be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... <snip>

            Hi,

            Welcome to the reflector.

            I would disconnect the grid capacitor from the previous stage (pin 2).
            The schematic shows 10V on the cathode, across the 680 Ohm
            cathode resistor (pin 1). This implies 10V/680 Ohms or about 14mA
            quiescent cathode current thru the 12BY7. With the grid capacitor disconnected, does the 12BY7 settle down to normal cathode current?
            I ask to have the grid capacitor disconnected in case the new
            coupling capacitor you installed is bad. (Is it rated at say 500V?)

            The idea of the cathode bias resistor is that the resting current
            thru the resistor serves as the bias for the tube. Ten volts
            at the cathode means -10V measured from control grid to cathode.

            If the cathode capacitor were shorted, you would get excessive
            cathode current (red plate), since the grid to cathode voltage would now be zero. But the cathode voltage would measure near zero
            with a shorted cathode capacitor, which you are not seeing.

            Have you considered that there may be a current path in the socket
            itself, due to a former flash-over or carbon trace? A bright light
            and a magnifying glass are called for here. Even if you can't see
            anything, it may be worthwhile to change out the socket before proceeding, given the flaky operation you are describing.

            Another thing to consider is that you may be operating the Apache on its side, causing a short within the 12BY7. The tube may operate well
            in a rig where its bottom is "down", and act up when operated on its side. Too bad you don't have a spare 12BY7.

            73,
            Ed Knobloch
          • R M Barlow
            There is a possibility that the 12BY7 is faulty (excessive grid emission), despite the fact that it seems to function ok, in the FT-101. Perhaps the dc
            Message 5 of 26 , Oct 18, 2013
              There is a possibility that the 12BY7 is faulty (excessive grid emission), despite the fact that it seems to function ok, in the FT-101. Perhaps the dc grid circuit resistance is lower in the FT-101 vs the TX-1??
               A problem that can occur in "high milage" tubes, involves migration of the cathodes oxide coating, to the control grid. The rate of this migration problem is greatly accelerated if the heater voltage is excessive, a common situation with todays higher line voltage levels.
               The unwanted oxide coating, on the control grid, causes it to begin emitting electrons--not a desired function of the control grid!
               This type of failure can manifest itself as a run away type condition. The tube seems to function ok, when "cold", but when the grid temperature rises sufficiently (due to heat radiated by the cathode), grid emission commences. Perhaps you checked the control grid voltage, when the tube was cold?? If grid emission is the cause of the problem, I would expect the grid voltage to rise in a positive direction, and the plate current to rise substantially, as the tube heats up.
                                             GL & 73 de Ron
              From: "tvman1954@..." <tvman1954@...>
              To: heathkit@yahoogroups.com
              Sent: Friday, October 18, 2013 8:05 PM
              Subject: [Heathkit:Yahoo] TX-1 Apache Problem Brand New Member



              I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.
               
              On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.
               
              The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can't see why it wouldn't be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....
                                                                         73 from Wade/KJ4WS




            • kj4ws
              Update on the TX-1 Apache. The 680 ohm 2 watt resistor on the Cathode is Brand New . It is a Carbon Composition resistor. Also, the 2 uf capacitor for the
              Message 6 of 26 , Oct 18, 2013

                Update on the TX-1 Apache.

                                                              The 680 ohm 2 watt resistor on the Cathode is Brand New . It is a Carbon Composition resistor.  Also, the 2 uf capacitor for the Cathode to Ground is a Brand New 450 vdc , made by NTE.  These are connected from the cathode pin to Ground. Yes, I did check the Polarity of the New cap very closely. The Positive Lead is connected to the Cathode. Any problems in the Cathode Circuit should be cured. At pin 2 or the Control grid, I have opened the circuit and placed a Brand New .01 @ 2 KV Ceramic Cap in series. So, any positive voltage to the Control Grid from the preceding stage  or a Leaky Cap in the Plate of the preceding stage should be cured. If the Cathode Capacitor was Shorted ... there would not be about 180 volts on the cathode after this thing gets cooking. The Cathode Resistor will sit there and self destruct if, you allow it. We are on the Third Cathode/680 ohm resistor. Therefore the Cathode Capacitor to ground can't be Shorted We will be looking for Carbon Tracks in the Tube Socket and all other suggestions. Ron, you have brought up several points that we will be checking. Maybe, I can find a 12BY7 that has not been used in RF Service for 30 years. Where in the world do you find a Brand New 12BY7 Tube?  Thanks to All who have replied so far.

                                                                                                                      73 DE Wade/KJ4WS



                ---In heathkit@yahoogroups.com, <vtrbest@...> wrote:

                There is a possibility that the 12BY7 is faulty (excessive grid emission), despite the fact that it seems to function ok, in the FT-101. Perhaps the dc grid circuit resistance is lower in the FT-101 vs the TX-1??
                 A problem that can occur in "high milage" tubes, involves migration of the cathodes oxide coating, to the control grid. The rate of this migration problem is greatly accelerated if the heater voltage is excessive, a common situation with todays higher line voltage levels.
                 The unwanted oxide coating, on the control grid, causes it to begin emitting electrons--not a desired function of the control grid!
                 This type of failure can manifest itself as a run away type condition. The tube seems to function ok, when "cold", but when the grid temperature rises sufficiently (due to heat radiated by the cathode), grid emission commences. Perhaps you checked the control grid voltage, when the tube was cold?? If grid emission is the cause of the problem, I would expect the grid voltage to rise in a positive direction, and the plate current to rise substantially, as the tube heats up.
                                               GL & 73 de Ron
                From: "tvman1954@..." <tvman1954@...>
                To: heathkit@yahoogroups.com
                Sent: Friday, October 18, 2013 8:05 PM
                Subject: [Heathkit:Yahoo] TX-1 Apache Problem Brand New Member



                I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.
                 
                On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.
                 
                The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can't see why it wouldn't be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....
                                                                           73 from Wade/KJ4WS




              • barry jones
                change the valve/tube base itself ,possibly tracking..   On Saturday, 19 October 2013, 7:57, tvman1954@gmail.com wrote:   Update on
                Message 7 of 26 , Oct 19, 2013
                  change the valve/tube base itself ,possibly tracking..
                   


                  On Saturday, 19 October 2013, 7:57, "tvman1954@..." <tvman1954@...> wrote:
                   
                  Update on the TX-1 Apache.
                                                                The 680 ohm 2 watt resistor on the Cathode is Brand New . It is a Carbon Composition resistor.  Also, the 2 uf capacitor for the Cathode to Ground is a Brand New 450 vdc , made by NTE.  These are connected from the cathode pin to Ground. Yes, I did check the Polarity of the New cap very closely. The Positive Lead is connected to the Cathode. Any problems in the Cathode Circuit should be cured. At pin 2 or the Control grid, I have opened the circuit and placed a Brand New .01 @ 2 KV Ceramic Cap in series. So, any positive voltage to the Control Grid from the preceding stage  or a Leaky Cap in the Plate of the preceding stage should be cured. If the Cathode Capacitor was Shorted ... there would not be about 180 volts on the cathode after this thing gets cooking. The Cathode Resistor will sit there and self destruct if, you allow it. We are on the Third Cathode/680 ohm resistor. Therefore the Cathode Capacitor to ground can't be Shorted We will be looking for Carbon Tracks in the Tube Socket and all other suggestions. Ron, you have brought up several points that we will be checking. Maybe, I can find a 12BY7 that has not been used in RF Service for 30 years. Where in the world do you find a Brand New 12BY7 Tube?  Thanks to All who have replied so far.
                                                                                                                        73 DE Wade/KJ4WS


                  ---In heathkit@yahoogroups.com, <vtrbest@...> wrote:

                  There is a possibility that the 12BY7 is faulty (excessive grid emission), despite the fact that it seems to function ok, in the FT-101. Perhaps the dc grid circuit resistance is lower in the FT-101 vs the TX-1??
                   A problem that can occur in "high milage" tubes, involves migration of the cathodes oxide coating, to the control grid. The rate of this migration problem is greatly accelerated if the heater voltage is excessive, a common situation with todays higher line voltage levels.
                   The unwanted oxide coating, on the control grid, causes it to begin emitting electrons--not a desired function of the control grid!
                   This type of failure can manifest itself as a run away type condition. The tube seems to function ok, when "cold", but when the grid temperature rises sufficiently (due to heat radiated by the cathode), grid emission commences. Perhaps you checked the control grid voltage, when the tube was cold?? If grid emission is the cause of the problem, I would expect the grid voltage to rise in a positive direction, and the plate current to rise substantially, as the tube heats up.
                                                 GL & 73 de Ron
                  From: "tvman1954@..." <tvman1954@...>
                  To: heathkit@yahoogroups.com
                  Sent: Friday, October 18, 2013 8:05 PM
                  Subject: [Heathkit:Yahoo] TX-1 Apache Problem Brand New Member



                  I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.
                   
                  On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.
                   
                  The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can't see why it wouldn't be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....
                                                                             73 from Wade/KJ4WS






                • Bry Carling
                  Hi Wade, This is an interesting troubleshooting story. I woul dlike to nklow the final outcome and what fixes it. There are plenty of new old stock 12BY7
                  Message 8 of 26 , Oct 19, 2013
                    Hi Wade,

                    This is an interesting troubleshooting story. I woul dlike to nklow the final outcome and what
                    fixes it. There are plenty of new old stock 12BY7 tubes around. You can find them, easily.
                    I may even have one here if you are stuck... Let me know.

                    It really does sound like a bad tune. I would also check the screen grid voltage and current
                    first. The voltage on your screen creed and/or beam forming plates in these driver tubes can
                    greatly influence cathode current too.

                    Bry, AF4K



                    On 18 Oct 2013 at 23:57, tvman1954@... wrote:

                    To: <heathkit@yahoogroups.com>
                    From: <tvman1954@...>
                    Date sent: 18 Oct 2013 23:57:27 -0700
                    Subject: [Heathkit:Yahoo] RE: TX-1 Apache Problem Brand New Member
                    Send reply to: heathkit@yahoogroups.com




                    Update on the TX-1 Apache.
                    The 680 ohm 2 watt resistor on the Cathode is Brand New . Itis
                    a Carbon Composition resistor.Also, the 2uf capacitor for the Cathode to Groundis a Brand
                    New 450 vdc , made by NTE. These are connected from the cathode pin to Ground. Yes, I
                    did check the Polarity of the New cap very closely. The Positive Lead is connected to the
                    Cathode. Any problems in the Cathode Circuit should be cured. At pin 2 or the Control grid, I
                    have opened the circuit and placed a Brand New .01 @ 2 KV Ceramic Cap in series. So, any
                    positive voltage to the Control Grid from the preceding stage or a Leaky Cap in the Plate of
                    the preceding stage should be cured. If the Cathode Capacitor was Shorted ... there would
                    not be about 180 volts on the cathode after this thing gets cooking. The Cathode Resistor will
                    sit there and self destruct if, you allow it. We are on the Third Cathode/680 ohm resistor.
                    Therefore the Cathode Capacitor to ground can't be Shorted We will be looking for Carbon
                    Tracks in the Tube Socket and all other suggestions. Ron, you have brought up several
                    points that we will be checking. Maybe, I can find a 12BY7 that has not been used in RF
                    Service for 30 years.Where in the world do you find a Brand New 12BY7 Tube? Thanks to
                    All who have replied so far.
                    73 DE Wade/KJ4WS


                    ---In heathkit@yahoogroups.com, <vtrbest@...> wrote:

                    There is apossibilitythat the 12BY7 is faulty (excessivegrid emission),
                    despite the fact that it seems to function ok, in the FT-101.Perhaps the dc
                    grid circuitresistance is lower in theFT-101 vs theTX-1??
                    Aproblem that can occurin "high milage" tubes,involvesmigration of
                    thecathodes oxide coating, to the control grid. The rate of thismigration
                    problem is greatly accelerated if theheater voltage is excessive, a common
                    situation withtodays higher line voltage levels.
                    The unwanted oxide coating, on the control grid, causes itto begin emitting
                    electrons--not a desired function of the control grid!
                    This type of failure can manifest itself as a run away type condition. The
                    tube seems to function ok, when "cold", butwhen the grid temperature rises
                    sufficiently (due to heat radiated by the cathode), grid emission commences.
                    Perhaps you checked the control grid voltage, when the tube was cold?? If
                    grid emission is the cause of the problem, I would expect the grid voltage to
                    rise in a positive direction, and the plate current to rise substantially, as the
                    tube heats up.
                    GL & 73 de Ron

                    From: "tvman1954@..." <tvman1954@...>
                    To: heathkit@yahoogroups.com
                    Sent: Friday, October 18, 2013 8:05 PM
                    Subject: [Heathkit:Yahoo] TX-1 Apache Problem Brand New Member



                    I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But
                    Modulation is the problem. I have changed the Cathode Resistor and Cap to
                    ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the
                    12BY7 is Grounded as it should be. B+ voltage is present on the Screen and
                    the Plate through the Driver Transformer. I have purchased and replaced the
                    Audio Driver Transformer Twice.

                    On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this
                    12BY7 tube. In my mind and now out of my mind, I think that everything has
                    been done. When placed in my FT-101 the 12BY7 Tube works great so we
                    know the tube is good.

                    The problem is really Distorted Audio from the Secondary of the Audio Driver
                    Transformer and also the Plate of the Tube will turn Cherry Red quite
                    quickly. Pin 1 the Cathode of the tube is going to over 180 volts instead of
                    10 volts as the Schematic references. Gentlemen, this thing has me
                    Stumped. It is apparent that the tube is turned on hard and drawing lots of
                    current. With 0 Volts on the Control Grid pin 2 I can't see why it wouldn't be
                    doing that. Please Help. I have never seen a Pentode wired as a Triode
                    much less Zero Bias on the Grid..... Help ... Help... What am I missing?
                    Someone has surely had this problem..... Also a Brand New Member here
                    just waiting to help others....
                    73 from Wade/KJ4WS
















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                  • herpsrwe
                    Here is what all those letters and numbers mean in a vacuum tube number http://tubesound.com/2010/04/09/rma-tube-numbering-code/
                    Message 9 of 26 , Oct 19, 2013

                       

                      Here is what all those "letters and numbers" mean in a vacuum tube number

                       http://tubesound.com/2010/04/09/rma-tube-numbering-code/

                       

                      I believe you could also use a 12BY7A

                       

                      Here is a Data Sheet for the 12BY7

                      http://www.nj7p.org/Common/Tube/SQL/Tube_query.php?Type=12by7

                      The Data Sheet also has a couple of Substitutions listed.

                       

                      Where do you normally buy tubes ? 

                      As everyone who owns tube type equipment has their own preference of where they buy their tubes...

                       

                      This is a common tube with plenty of them still around, for around $12.00...

                       

                      Bill

                       



                      ---In heathkit@yahoogroups.com, <bcarling@...> wrote:

                      Hi Wade,

                      This is an interesting troubleshooting story. I woul dlike to nklow the final outcome and what
                      fixes it. There are plenty of new old stock 12BY7 tubes around. You can find them, easily.
                      I may even have one here if you are stuck... Let me know.

                      It really does sound like a bad tune. I would also check the screen grid voltage and current
                      first. The voltage on your screen creed and/or beam forming plates in these driver tubes can
                      greatly influence cathode current too.

                      Bry, AF4K



                      On 18 Oct 2013 at 23:57, tvman1954@... wrote:

                      To: <heathkit@yahoogroups.com>
                      From: <tvman1954@...>
                      Date sent: 18 Oct 2013 23:57:27 -0700
                      Subject: [Heathkit:Yahoo] RE: TX-1 Apache Problem Brand New Member
                      Send reply to: heathkit@yahoogroups.com




                      Update on the TX-1 Apache.
                      The 680 ohm 2 watt resistor on the Cathode is Brand New . Itis
                      a Carbon Composition resistor.Also, the 2uf capacitor for the Cathode to Groundis a Brand
                      New 450 vdc , made by NTE. These are connected from the cathode pin to Ground. Yes, I
                      did check the Polarity of the New cap very closely. The Positive Lead is connected to the
                      Cathode. Any problems in the Cathode Circuit should be cured. At pin 2 or the Control grid, I
                      have opened the circuit and placed a Brand New .01 @ 2 KV Ceramic Cap in series. So, any
                      positive voltage to the Control Grid from the preceding stage or a Leaky Cap in the Plate of
                      the preceding stage should be cured. If the Cathode Capacitor was Shorted ... there would
                      not be about 180 volts on the cathode after this thing gets cooking. The Cathode Resistor will
                      sit there and self destruct if, you allow it. We are on the Third Cathode/680 ohm resistor.
                      Therefore the Cathode Capacitor to ground can't be Shorted We will be looking for Carbon
                      Tracks in the Tube Socket and all other suggestions. Ron, you have brought up several
                      points that we will be checking. Maybe, I can find a 12BY7 that has not been used in RF
                      Service for 30 years.Where in the world do you find a Brand New 12BY7 Tube? Thanks to
                      All who have replied so far.
                      73 DE Wade/KJ4WS


                      ---In heathkit@yahoogroups.com, <vtrbest@...> wrote:

                      There is apossibilitythat the 12BY7 is faulty (excessivegrid emission),
                      despite the fact that it seems to function ok, in the FT-101.Perhaps the dc
                      grid circuitresistance is lower in theFT-101 vs theTX-1??
                      Aproblem that can occurin "high milage" tubes,involvesmigration of
                      thecathodes oxide coating, to the control grid. The rate of thismigration
                      problem is greatly accelerated if theheater voltage is excessive, a common
                      situation withtodays higher line voltage levels.
                      The unwanted oxide coating, on the control grid, causes itto begin emitting
                      electrons--not a desired function of the control grid!
                      This type of failure can manifest itself as a run away type condition. The
                      tube seems to function ok, when "cold", butwhen the grid temperature rises
                      sufficiently (due to heat radiated by the cathode), grid emission commences.
                      Perhaps you checked the control grid voltage, when the tube was cold?? If
                      grid emission is the cause of the problem, I would expect the grid voltage to
                      rise in a positive direction, and the plate current to rise substantially, as the
                      tube heats up.
                      GL & 73 de Ron

                      From: "tvman1954@..." <tvman1954@...>
                      To: heathkit@yahoogroups.com
                      Sent: Friday, October 18, 2013 8:05 PM
                      Subject: [Heathkit:Yahoo] TX-1 Apache Problem Brand New Member



                      I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But
                      Modulation is the problem. I have changed the Cathode Resistor and Cap to
                      ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the
                      12BY7 is Grounded as it should be. B+ voltage is present on the Screen and
                      the Plate through the Driver Transformer. I have purchased and replaced the
                      Audio Driver Transformer Twice.

                      On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this
                      12BY7 tube. In my mind and now out of my mind, I think that everything has
                      been done. When placed in my FT-101 the 12BY7 Tube works great so we
                      know the tube is good.

                      The problem is really Distorted Audio from the Secondary of the Audio Driver
                      Transformer and also the Plate of the Tube will turn Cherry Red quite
                      quickly. Pin 1 the Cathode of the tube is going to over 180 volts instead of
                      10 volts as the Schematic references. Gentlemen, this thing has me
                      Stumped. It is apparent that the tube is turned on hard and drawing lots of
                      current. With 0 Volts on the Control Grid pin 2 I can't see why it wouldn't be
                      doing that. Please Help. I have never seen a Pentode wired as a Triode
                      much less Zero Bias on the Grid..... Help ... Help... What am I missing?
                      Someone has surely had this problem..... Also a Brand New Member here
                      just waiting to help others....
                      73 from Wade/KJ4WS
















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                    • R M Barlow
                      Hi Wade,  When you say that you have inserted a .01 cap in the control grid lead, do you mean that it has been inserted between pin 2 of the 12BY7 and the
                      Message 10 of 26 , Oct 19, 2013
                        Hi Wade,
                         When you say that you have inserted a .01 cap in the control grid lead, do you mean that it has been inserted between pin 2 of the 12BY7 and the audio gain pot, or is it located as per the schematic--that is between the plate of V2 (12AU7,) and the top end of the pot???
                         If the former, unless you have also added a resistor from pin 2 to chassis ground, the control grid is now floating, from a DC perspective. I suggest that should install the .01 in the original location, if that is the case.
                         
                         Many/most tubes go into the plate current cutoff mode, when the grid is left open, for dc, but the 12by7 may be an exception??
                         For example, when the screen grid is allowed to "float", with most tubes, the plate current will drop to or nearly to zero. Not so with radial beem tetrodes, such as the 4CX250. If the screen grid is allowed to float, with these types of tubes, the screen grid voltage will soar, and the plate current will do likewise. This is due to secondary emission effects.
                         
                         I was too tired, when I previously relied, to realize that a voltage drop of 180 volts across 680 ohms would indicate that the tube is drawing nearly 270 mils of plate current!!! That  seems surreal! I would have expected the plate of the tube would quickly do a complete melt down, at that level, and that your driver transformer would fail almost immediately! Also, the 680 ohm cathode bias resistor would be dissipating  45+ watts, which would quickly destroy it!!
                         I suspect that you may be getting some RF into your meter (DVM???) circuitry, causing erroneous readings. Shunting the meter leads with a .01 cap may correct this problem, but perhaps not, due to the long leads, to the meter. A shunting cap placed closer to the meter itself, would be more effective.
                                                                       GL & 73 de Ron
                        From: barry jones <barrymw1fdu@...>
                        To: heathkit@yahoogroups.com
                        Sent: Saturday, October 19, 2013 7:05 AM
                        Subject: Re: [Heathkit:Yahoo] RE: TX-1 Apache Problem Brand New Member



                        change the valve/tube base itself ,possibly tracking..
                         


                        On Saturday, 19 October 2013, 7:57, "tvman1954@..." <tvman1954@...> wrote:
                         
                        Update on the TX-1 Apache.
                                                                      The 680 ohm 2 watt resistor on the Cathode is Brand New . It is a Carbon Composition resistor.  Also, the 2 uf capacitor for the Cathode to Ground is a Brand New 450 vdc , made by NTE.  These are connected from the cathode pin to Ground. Yes, I did check the Polarity of the New cap very closely. The Positive Lead is connected to the Cathode. Any problems in the Cathode Circuit should be cured. At pin 2 or the Control grid, I have opened the circuit and placed a Brand New .01 @ 2 KV Ceramic Cap in series. So, any positive voltage to the Control Grid from the preceding stage  or a Leaky Cap in the Plate of the preceding stage should be cured. If the Cathode Capacitor was Shorted ... there would not be about 180 volts on the cathode after this thing gets cooking. The Cathode Resistor will sit there and self destruct if, you allow it. We are on the Third Cathode/680 ohm resistor. Therefore the Cathode Capacitor to ground can&apos;t be Shorted We will be looking for Carbon Tracks in the Tube Socket and all other suggestions. Ron, you have brought up several points that we will be checking. Maybe, I can find a 12BY7 that has not been used in RF Service for 30 years. Where in the world do you find a Brand New 12BY7 Tube?  Thanks to All who have replied so far.
                                                                                                                              73 DE Wade/KJ4WS


                        ---In heathkit@yahoogroups.com, <vtrbest@...> wrote:

                        There is a possibility that the 12BY7 is faulty (excessive grid emission), despite the fact that it seems to function ok, in the FT-101. Perhaps the dc grid circuit resistance is lower in the FT-101 vs the TX-1??
                         A problem that can occur in "high milage" tubes, involves migration of the cathodes oxide coating, to the control grid. The rate of this migration problem is greatly accelerated if the heater voltage is excessive, a common situation with todays higher line voltage levels.
                         The unwanted oxide coating, on the control grid, causes it to begin emitting electrons--not a desired function of the control grid!
                         This type of failure can manifest itself as a run away type condition. The tube seems to function ok, when "cold", but when the grid temperature rises sufficiently (due to heat radiated by the cathode), grid emission commences. Perhaps you checked the control grid voltage, when the tube was cold?? If grid emission is the cause of the problem, I would expect the grid voltage to rise in a positive direction, and the plate current to rise substantially, as the tube heats up.
                                                       GL & 73 de Ron
                        From: "tvman1954@..." <tvman1954@...>
                        To: heathkit@yahoogroups.com
                        Sent: Friday, October 18, 2013 8:05 PM
                        Subject: [Heathkit:Yahoo] TX-1 Apache Problem Brand New Member



                        I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.
                         
                        On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.
                         
                        The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can&apos;t see why it wouldn&apos;t be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....
                                                                                   73 from Wade/KJ4WS










                      • kj4ws
                        Hello to Ron and Thanks, There is no real RF to get into the meter leads unless I throw the Receive/Transmit Switch on the front panel of the transmitter. I
                        Message 11 of 26 , Oct 19, 2013

                          Hello to Ron and Thanks,

                                                                   There is no real RF to get into the meter leads unless I throw the Receive/Transmit Switch on the front panel of the transmitter. I have removed the 12BY7 Tube and the Cathode is Zero Voltage while it is out of the rig.  The Audio Pre-Amp circuits are alive and working all the time in this Beast but, Plate Voltage is only applied to the (2) 6146 PA Outputs and the (2) 6CA7 Modulator Tubes when the Standby/Transmit Switch is Thrown to Transmit. YOU HAVE MADE A GOOD CALL on the Floating Grid ! The 500K Ohm Pot used as the Level Control ( I believe R3 thanks to bad eyes ) was isolated by the Extra .01 Cap. I have since replaced the 500 K Ohm Control and placed the .01 Cap ( new ) 2.5 KV in the circuit where the Schematic indicates. I have never allowed one of the several 680 ohm Cathode Resistors to full Self Destruct But, they have gotten quite warm. I do know that with this posting, I am out of ideas for anything except the tube. As a radio collector of sorts, there were (2) 12BY7 tubes that work well at my disposal. The Email Address says it all tvman1954@... ..... I am now on my way to the Storage Building which is out back, to see if, one of those 5 gallon buckets have a good one in the box. Ron, thanks to you and the Group for all of your help. The Weird Problem still Plagues this poor old 1958 piece of equipment. Cosmetically it is Beautiful. Any and All ideas are still needed.

                                                                                                      Abundant 73 to All de Wade/KJ4WS 

                                                                                                   .



                          ---In heathkit@yahoogroups.com, <heathkit@yahoogroups.com> wrote:

                          Hi Wade,
                           When you say that you have inserted a .01 cap in the control grid lead, do you mean that it has been inserted between pin 2 of the 12BY7 and the audio gain pot, or is it located as per the schematic--that is between the plate of V2 (12AU7,) and the top end of the pot???
                           If the former, unless you have also added a resistor from pin 2 to chassis ground, the control grid is now floating, from a DC perspective. I suggest that should install the .01 in the original location, if that is the case.
                           
                           Many/most tubes go into the plate current cutoff mode, when the grid is left open, for dc, but the 12by7 may be an exception??
                           For example, when the screen grid is allowed to "float", with most tubes, the plate current will drop to or nearly to zero. Not so with radial beem tetrodes, such as the 4CX250. If the screen grid is allowed to float, with these types of tubes, the screen grid voltage will soar, and the plate current will do likewise. This is due to secondary emission effects.
                           
                           I was too tired, when I previously relied, to realize that a voltage drop of 180 volts across 680 ohms would indicate that the tube is drawing nearly 270 mils of plate current!!! That  seems surreal! I would have expected the plate of the tube would quickly do a complete melt down, at that level, and that your driver transformer would fail almost immediately! Also, the 680 ohm cathode bias resistor would be dissipating  45+ watts, which would quickly destroy it!!
                           I suspect that you may be getting some RF into your meter (DVM???) circuitry, causing erroneous readings. Shunting the meter leads with a .01 cap may correct this problem, but perhaps not, due to the long leads, to the meter. A shunting cap placed closer to the meter itself, would be more effective.
                                                                         GL & 73 de Ron
                          From: barry jones <barrymw1fdu@...>
                          To: heathkit@yahoogroups.com
                          Sent: Saturday, October 19, 2013 7:05 AM
                          Subject: Re: [Heathkit:Yahoo] RE: TX-1 Apache Problem Brand New Member



                          change the valve/tube base itself ,possibly tracking..
                           


                          On Saturday, 19 October 2013, 7:57, "tvman1954@..." <tvman1954@...> wrote:
                           
                          Update on the TX-1 Apache.
                                                                        The 680 ohm 2 watt resistor on the Cathode is Brand New . It is a Carbon Composition resistor.  Also, the 2 uf capacitor for the Cathode to Ground is a Brand New 450 vdc , made by NTE.  These are connected from the cathode pin to Ground. Yes, I did check the Polarity of the New cap very closely. The Positive Lead is connected to the Cathode. Any problems in the Cathode Circuit should be cured. At pin 2 or the Control grid, I have opened the circuit and placed a Brand New .01 @ 2 KV Ceramic Cap in series. So, any positive voltage to the Control Grid from the preceding stage  or a Leaky Cap in the Plate of the preceding stage should be cured. If the Cathode Capacitor was Shorted ... there would not be about 180 volts on the cathode after this thing gets cooking. The Cathode Resistor will sit there and self destruct if, you allow it. We are on the Third Cathode/680 ohm resistor. Therefore the Cathode Capacitor to ground can&apos;t be Shorted We will be looking for Carbon Tracks in the Tube Socket and all other suggestions. Ron, you have brought up several points that we will be checking. Maybe, I can find a 12BY7 that has not been used in RF Service for 30 years. Where in the world do you find a Brand New 12BY7 Tube?  Thanks to All who have replied so far.
                                                                                                                                73 DE Wade/KJ4WS


                          ---In heathkit@yahoogroups.com, <vtrbest@...> wrote:

                          There is a possibility that the 12BY7 is faulty (excessive grid emission), despite the fact that it seems to function ok, in the FT-101. Perhaps the dc grid circuit resistance is lower in the FT-101 vs the TX-1??
                           A problem that can occur in "high milage" tubes, involves migration of the cathodes oxide coating, to the control grid. The rate of this migration problem is greatly accelerated if the heater voltage is excessive, a common situation with todays higher line voltage levels.
                           The unwanted oxide coating, on the control grid, causes it to begin emitting electrons--not a desired function of the control grid!
                           This type of failure can manifest itself as a run away type condition. The tube seems to function ok, when "cold", but when the grid temperature rises sufficiently (due to heat radiated by the cathode), grid emission commences. Perhaps you checked the control grid voltage, when the tube was cold?? If grid emission is the cause of the problem, I would expect the grid voltage to rise in a positive direction, and the plate current to rise substantially, as the tube heats up.
                                                         GL & 73 de Ron
                          From: "tvman1954@..." <tvman1954@...>
                          To: heathkit@yahoogroups.com
                          Sent: Friday, October 18, 2013 8:05 PM
                          Subject: [Heathkit:Yahoo] TX-1 Apache Problem Brand New Member



                          I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.
                           
                          On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.
                           
                          The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can&apos;t see why it wouldn&apos;t be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....
                                                                                     73 from Wade/KJ4WS










                        • Howie
                          What about carbon tracking on the tube base? ... From: tvman1954@gmail.com To: heathkit@yahoogroups.com Sent: Saturday, October 19, 2013 3:05 PM Subject: RE:
                          Message 12 of 26 , Oct 19, 2013
                            
                            What about carbon tracking on the tube base?
                             
                            ----- Original Message -----
                            Sent: Saturday, October 19, 2013 3:05 PM
                            Subject: RE: Re: [Heathkit:Yahoo] RE: TX-1 Apache Problem Brand New Member

                             

                            Hello to Ron and Thanks,

                                                                     There is no real RF to get into the meter leads unless I throw the Receive/Transmit Switch on the front panel of the transmitter. I have removed the 12BY7 Tube and the Cathode is Zero Voltage while it is out of the rig.  The Audio Pre-Amp circuits are alive and working all the time in this Beast but, Plate Voltage is only applied to the (2) 6146 PA Outputs and the (2) 6CA7 Modulator Tubes when the Standby/Transmit Switch is Thrown to Transmit. YOU HAVE MADE A GOOD CALL on the Floating Grid ! The 500K Ohm Pot used as the Level Control ( I believe R3 thanks to bad eyes ) was isolated by the Extra .01 Cap. I have since replaced the 500 K Ohm Control and placed the .01 Cap ( new ) 2.5 KV in the circuit where the Schematic indicates. I have never allowed one of the several 680 ohm Cathode Resistors to full Self Destruct But, they have gotten quite warm. I do know that with this posting, I am out of ideas for anything except the tube. As a radio collector of sorts, there were (2) 12BY7 tubes that work well at my disposal. The Email Address says it all tvman1954@... ..... I am now on my way to the Storage Building which is out back, to see if, one of those 5 gallon buckets have a good one in the box. Ron, thanks to you and the Group for all of your help. The Weird Problem still Plagues this poor old 1958 piece of equipment. Cosmetically it is Beautiful. Any and All ideas are still needed.

                                                                                                        Abundant 73 to All de Wade/KJ4WS 

                                                                                                     .



                            ---In heathkit@yahoogroups.com, <heathkit@yahoogroups.com> wrote:

                            Hi Wade,
                             When you say that you have inserted a .01 cap in the control grid lead, do you mean that it has been inserted between pin 2 of the 12BY7 and the audio gain pot, or is it located as per the schematic--that is between the plate of V2 (12AU7,) and the top end of the pot???
                             If the former, unless you have also added a resistor from pin 2 to chassis ground, the control grid is now floating, from a DC perspective. I suggest that should install the .01 in the original location, if that is the case.
                             
                             Many/most tubes go into the plate current cutoff mode, when the grid is left open, for dc, but the 12by7 may be an exception??
                             For example, when the screen grid is allowed to "float", with most tubes, the plate current will drop to or nearly to zero. Not so with radial beem tetrodes, such as the 4CX250. If the screen grid is allowed to float, with these types of tubes, the screen grid voltage will soar, and the plate current will do likewise. This is due to secondary emission effects.
                             
                             I was too tired, when I previously relied, to realize that a voltage drop of 180 volts across 680 ohms would indicate that the tube is drawing nearly 270 mils of plate current!!! That  seems surreal! I would have expected the plate of the tube would quickly do a complete melt down, at that level, and that your driver transformer would fail almost immediately! Also, the 680 ohm cathode bias resistor would be dissipating  45+ watts, which would quickly destroy it!!
                             I suspect that you may be getting some RF into your meter (DVM???) circuitry, causing erroneous readings. Shunting the meter leads with a .01 cap may correct this problem, but perhaps not, due to the long leads, to the meter. A shunting cap placed closer to the meter itself, would be more effective.
                                                                           GL & 73 de Ron
                            From: barry jones <barrymw1fdu@...>
                            To: heathkit@yahoogroups.com
                            Sent: Saturday, October 19, 2013 7:05 AM
                            Subject: Re: [Heathkit:Yahoo] RE: TX-1 Apache Problem Brand New Member



                            change the valve/tube base itself ,possibly tracking..
                             


                            On Saturday, 19 October 2013, 7:57, "tvman1954@..." <tvman1954@...> wrote:
                             
                            Update on the TX-1 Apache.
                                                                          The 680 ohm 2 watt resistor on the Cathode is Brand New . It is a Carbon Composition resistor.  Also, the 2 uf capacitor for the Cathode to Ground is a Brand New 450 vdc , made by NTE.  These are connected from the cathode pin to Ground. Yes, I did check the Polarity of the New cap very closely. The Positive Lead is connected to the Cathode. Any problems in the Cathode Circuit should be cured. At pin 2 or the Control grid, I have opened the circuit and placed a Brand New .01 @ 2 KV Ceramic Cap in series. So, any positive voltage to the Control Grid from the preceding stage  or a Leaky Cap in the Plate of the preceding stage should be cured. If the Cathode Capacitor was Shorted ... there would not be about 180 volts on the cathode after this thing gets cooking. The Cathode Resistor will sit there and self destruct if, you allow it. We are on the Third Cathode/680 ohm resistor. Therefore the Cathode Capacitor to ground can&apos;t be Shorted We will be looking for Carbon Tracks in the Tube Socket and all other suggestions. Ron, you have brought up several points that we will be checking. Maybe, I can find a 12BY7 that has not been used in RF Service for 30 years. Where in the world do you find a Brand New 12BY7 Tube?  Thanks to All who have replied so far.
                                                                                                                                  73 DE Wade/KJ4WS


                            ---In heathkit@yahoogroups.com, <vtrbest@...> wrote:

                            There is a possibility that the 12BY7 is faulty (excessive grid emission), despite the fact that it seems to function ok, in the FT-101. Perhaps the dc grid circuit resistance is lower in the FT-101 vs the TX-1??
                             A problem that can occur in "high milage" tubes, involves migration of the cathodes oxide coating, to the control grid. The rate of this migration problem is greatly accelerated if the heater voltage is excessive, a common situation with todays higher line voltage levels.
                             The unwanted oxide coating, on the control grid, causes it to begin emitting electrons--not a desired function of the control grid!
                             This type of failure can manifest itself as a run away type condition. The tube seems to function ok, when "cold", but when the grid temperature rises sufficiently (due to heat radiated by the cathode), grid emission commences. Perhaps you checked the control grid voltage, when the tube was cold?? If grid emission is the cause of the problem, I would expect the grid voltage to rise in a positive direction, and the plate current to rise substantially, as the tube heats up.
                                                           GL & 73 de Ron
                            From: "tvman1954@..." <tvman1954@...>
                            To: heathkit@yahoogroups.com
                            Sent: Friday, October 18, 2013 8:05 PM
                            Subject: [Heathkit:Yahoo] TX-1 Apache Problem Brand New Member



                            I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.
                             
                            On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.
                             
                            The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can&apos;t see why it wouldn&apos;t be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....
                                                                                       73 from Wade/KJ4WS










                          • Wade Staggs
                            Hello Bry, This is really a straight forward and easy circuit. The Plate and Screen pins are actually soldered to each other and both have direct connection to
                            Message 13 of 26 , Oct 20, 2013
                              Hello Bry,
                                              This is really a straight forward and easy circuit. The Plate and Screen pins are actually soldered to each other and both have direct connection to the Primary of the Audio Driver Transformer. Pin 9 of the 12BY7 is tied straight to ground. And Pin 2 or the Control Grid has the incoming signal through a .01 Ceramic Capacitor. So, the Screen Voltage has to be there. Working on this stuff siince early 1971, I have never seen any trouble like this. My Girlfriend Brenda, has threatened to catch me not looking and pay someone to hide this bugger from me. I may as well double up on the Rogaine !!! The hair is slowly being pulled out. My friend Les/W4SAV, has an NOS 12BY7 waiting for me. I will pick it up tomorrow. Thanks to you and Ron. We will soon see if it is Unwanted Grid Emission.
                                                                                                                               73 de Wade/KJ4WS
                            • R M Barlow
                              Hi Wade,  Just a suggestion; Prior to applying power, connect your VOM to read the voltage on the 12BY7 cathode, referenced to chassis ground. In other
                              Message 14 of 26 , Oct 20, 2013
                                Hi Wade,
                                 Just a suggestion; Prior to applying power, connect your VOM to read the voltage on the 12BY7 cathode, referenced to chassis ground. In other words, connect the VOM across the 680 ohm resistor.
                                 Monitor the voltage drop across the resistor, when you apply power. If it rises to a value that exceeds about 16 volts, immediately remove the power, and post that info, on this reflector, before proceeding.
                                 
                                 I did not readily find voltage measurement info, on the TX-1, only a schematic. It does, however, include info on the power xfmr voltage, which would seem to indicate that the plate (and screen) voltage, on the 12BY7 is ~ 300 volts. The max plate dissipation rating of the BY7 is 6.5 watts, and the screen rating is 1.1 watt. Anything in excess of this level will greatly reduce tube life. A glowing plate, on this type of tube, will certainly ruin the tube in a very brief period of time.
                                 A 16 volt drop across the 680 ohm resistor, indicates a plate and screen current in the vicinity of 25 mils, which is approximately at the max limit. If the cathode current exceeds this value, something is awry, and should be corrected, before your new tube becomes damaged.
                                 
                                 My research did not reveal any suggested ratings, for a triode connected 12BY7. However, the stated screen voltage limit, for the 12BY7, is 180 volts (Tung Sol states that 190 volts is the max limit, for their version of the BY7).  
                                 Did this xmtr previously work ok, in the recent past, Wade? I am wondering about unnoticed mods?? 
                                 
                                                      Again, GL  & 73
                                                      Ron (also an ex tv svc guy).
                                From: Wade Staggs <tvman1954@...>
                                To: heathkit@yahoogroups.com
                                Sent: Sunday, October 20, 2013 7:38 PM
                                Subject: [Heathkit:Yahoo] Re: TX-1 Apache Problem Brand New Member



                                Hello Bry,
                                                This is really a straight forward and easy circuit. The Plate and Screen pins are actually soldered to each other and both have direct connection to the Primary of the Audio Driver Transformer. Pin 9 of the 12BY7 is tied straight to ground. And Pin 2 or the Control Grid has the incoming signal through a .01 Ceramic Capacitor. So, the Screen Voltage has to be there. Working on this stuff siince early 1971, I have never seen any trouble like this. My Girlfriend Brenda, has threatened to catch me not looking and pay someone to hide this bugger from me. I may as well double up on the Rogaine !!! The hair is slowly being pulled out. My friend Les/W4SAV, has an NOS 12BY7 waiting for me. I will pick it up tomorrow. Thanks to you and Ron. We will soon see if it is Unwanted Grid Emission.
                                                                                                                                 73 de Wade/KJ4WS
                              • k4pf@juno.com
                                ... ... Hi, Wade I would change out the 9 pin socket before sacrificing another 12BY7. There could be a conductive path in the socket from the plate or
                                Message 15 of 26 , Oct 20, 2013
                                  > Wade Staggs <tvman1954@...> wrote
                                  <snip>
                                  > My friend Les/W4SAV, has an NOS 12BY7 waiting for me. I will pick it up tomorrow. Thanks to you and Ron. We will soon see if it is Unwanted Grid Emission.

                                  Hi, Wade

                                  I would change out the 9 pin socket before sacrificing
                                  another 12BY7. There could be a conductive path
                                  in the socket from the plate or screen pins to control grid,
                                  causing the runaway cathode current.
                                  That's a very high impedance circuit, so the path may have resistance
                                  higher than a VOM can measure, and still drive the grid positive.

                                  It would be wise to add a 470K resistor
                                  directly from the control grid (pin 2) to ground.
                                  Heath depended on the DC return thru the level
                                  control pot, which is a poor design. If that pot has a poor wiper function (it is now 50 plus years old), the grid will be floating,
                                  and bad results will happen.

                                  The 470K added resistor won't hurt anything, and is good insurance.

                                  73,
                                  Ed Knobloch
                                • Howie
                                  The tx-1 schem I have has all the tube voltages already on the schematic at all the tubes. The plate and screen voltage is 350V. ... From: R M Barlow To:
                                  Message 16 of 26 , Oct 20, 2013
                                    The tx-1 schem I have has all the tube voltages already on the schematic at all the tubes.
                                     
                                    The plate and screen voltage is 350V.
                                     
                                     
                                     
                                     
                                    ----- Original Message -----
                                    Sent: Sunday, October 20, 2013 11:27 PM
                                    Subject: Re: [Heathkit:Yahoo] Re: TX-1 Apache Problem Brand New Member

                                     

                                    Hi Wade,
                                     Just a suggestion; Prior to applying power, connect your VOM to read the voltage on the 12BY7 cathode, referenced to chassis ground. In other words, connect the VOM across the 680 ohm resistor.
                                     Monitor the voltage drop across the resistor, when you apply power. If it rises to a value that exceeds about 16 volts, immediately remove the power, and post that info, on this reflector, before proceeding.
                                     
                                     I did not readily find voltage measurement info, on the TX-1, only a schematic. It does, however, include info on the power xfmr voltage, which would seem to indicate that the plate (and screen) voltage, on the 12BY7 is ~ 300 volts. The max plate dissipation rating of the BY7 is 6.5 watts, and the screen rating is 1.1 watt. Anything in excess of this level will greatly reduce tube life. A glowing plate, on this type of tube, will certainly ruin the tube in a very brief period of time.
                                     A 16 volt drop across the 680 ohm resistor, indicates a plate and screen current in the vicinity of 25 mils, which is approximately at the max limit. If the cathode current exceeds this value, something is awry, and should be corrected, before your new tube becomes damaged.
                                     
                                     My research did not reveal any suggested ratings, for a triode connected 12BY7. However, the stated screen voltage limit, for the 12BY7, is 180 volts (Tung Sol states that 190 volts is the max limit, for their version of the BY7).  
                                     Did this xmtr previously work ok, in the recent past, Wade? I am wondering about unnoticed mods?? 
                                     
                                                          Again, GL  & 73
                                                          Ron (also an ex tv svc guy).
                                    From: Wade Staggs <tvman1954@...>
                                    To: heathkit@yahoogroups.com
                                    Sent: Sunday, October 20, 2013 7:38 PM
                                    Subject: [Heathkit:Yahoo] Re: TX-1 Apache Problem Brand New Member



                                    Hello Bry,
                                                    This is really a straight forward and easy circuit. The Plate and Screen pins are actually soldered to each other and both have direct connection to the Primary of the Audio Driver Transformer. Pin 9 of the 12BY7 is tied straight to ground. And Pin 2 or the Control Grid has the incoming signal through a .01 Ceramic Capacitor. So, the Screen Voltage has to be there. Working on this stuff siince early 1971, I have never seen any trouble like this. My Girlfriend Brenda, has threatened to catch me not looking and pay someone to hide this bugger from me. I may as well double up on the Rogaine !!! The hair is slowly being pulled out. My friend Les/W4SAV, has an NOS 12BY7 waiting for me. I will pick it up tomorrow. Thanks to you and Ron. We will soon see if it is Unwanted Grid Emission.
                                                                                                                                     73 de Wade/KJ4WS

                                  • K5MYJ
                                    You could connect a jumper between the control grid and ground for testing. Bob Macklin K5MYJ Seattle, Wa. Real Radios Glow In The Dark ... From:
                                    Message 17 of 26 , Oct 20, 2013
                                      You could connect a jumper between the control grid and ground for testing.

                                      Bob Macklin
                                      K5MYJ
                                      Seattle, Wa.
                                      "Real Radios Glow In The Dark"

                                      ----- Original Message -----
                                      From: <k4pf@...>
                                      To: <heathkit@yahoogroups.com>
                                      Sent: Sunday, October 20, 2013 9:27 PM
                                      Subject: Re: [Heathkit:Yahoo] Re: TX-1 Apache Problem Brand New Member


                                      >
                                      >
                                      >> Wade Staggs <tvman1954@...> wrote
                                      > <snip>
                                      >> My friend Les/W4SAV, has an NOS 12BY7 waiting for me. I will pick it up
                                      >> tomorrow. Thanks to you and Ron. We will soon see if it is Unwanted Grid
                                      >> Emission.
                                      >
                                      > Hi, Wade
                                      >
                                      > I would change out the 9 pin socket before sacrificing
                                      > another 12BY7. There could be a conductive path
                                      > in the socket from the plate or screen pins to control grid,
                                      > causing the runaway cathode current.
                                      > That's a very high impedance circuit, so the path may have resistance
                                      > higher than a VOM can measure, and still drive the grid positive.
                                      >
                                      > It would be wise to add a 470K resistor
                                      > directly from the control grid (pin 2) to ground.
                                      > Heath depended on the DC return thru the level
                                      > control pot, which is a poor design. If that pot has a poor wiper
                                      > function (it is now 50 plus years old), the grid will be floating,
                                      > and bad results will happen.
                                      >
                                      > The 470K added resistor won't hurt anything, and is good insurance.
                                      >
                                      > 73,
                                      > Ed Knobloch
                                      >
                                      >
                                      > ------------------------------------
                                      >
                                      > --------------------------------------------------------------------------
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                                    • w6ou
                                      There may be some oscillation or excessive levels somewhere in the audio circuit which is overdriving the 12BY7. What is the amplitude of the audio signal at
                                      Message 18 of 26 , Oct 21, 2013

                                        There may be some oscillation or excessive levels somewhere in the audio circuit which is overdriving the 12BY7.  What is the amplitude of the audio signal at the input of the 12BY7?  Is your scope capable of displaying RF signals which may be present at the 12BY7? Try removing the 12AU7 tube which drives the 12BY7.



                                        ---In heathkit@yahoogroups.com, <tvman1954@...> wrote:

                                        I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.

                                         

                                        On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.

                                         

                                        The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can't see why it wouldn't be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....

                                                                                                   73 from Wade/KJ4WS

                                      • tjb813
                                        I would guess from what you describe, the coupling capacitor onthe grid of the 12BY7 is leaky. It will measure ok when the rig is powered down, but will leak
                                        Message 19 of 26 , Oct 23, 2013

                                          I would guess from what you describe, the coupling capacitor onthe grid of the 12BY7 is leaky.   It will measure ok when the rig is powered down, but will leak when there is plate voltage on the 12au7.   If the grid of the 12BY7 is driven positive (from the leaky coupling cap) it will exhibit the behaviour you describe exactly.

                                           

                                          Good Luck, stay with it,

                                          KD8CN

                                          Tim 



                                          ---In heathkit@yahoogroups.com, <heathkit@yahoogroups.com> wrote:

                                          There may be some oscillation or excessive levels somewhere in the audio circuit which is overdriving the 12BY7.  What is the amplitude of the audio signal at the input of the 12BY7?  Is your scope capable of displaying RF signals which may be present at the 12BY7? Try removing the 12AU7 tube which drives the 12BY7.



                                          ---In heathkit@yahoogroups.com, <tvman1954@...> wrote:

                                          I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.

                                           

                                          On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.

                                           

                                          The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can't see why it wouldn't be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....

                                                                                                     73 from Wade/KJ4WS

                                        • R M Barlow
                                          Hi Wade,  If you haven t resolved this problem, yet, remove the 12by7 tube from its socket, and apply AC power to the xmtr. Check the voltage levels on each
                                          Message 20 of 26 , Oct 23, 2013
                                            Hi Wade,
                                             If you haven't resolved this problem, yet, remove the 12by7 tube from its socket, and apply AC power to the xmtr. Check the voltage levels on each of the 9 pins, AC and DC, and report your findings to us.
                                                                               GL & 73 de Ron
                                            From: "tjb813@..." <tjb813@...>
                                            To: heathkit@yahoogroups.com
                                            Sent: Wednesday, October 23, 2013 8:09 AM
                                            Subject: [Heathkit:Yahoo] RE: RE: TX-1 Apache Problem Brand New Member



                                            I would guess from what you describe, the coupling capacitor onthe grid of the 12BY7 is leaky.   It will measure ok when the rig is powered down, but will leak when there is plate voltage on the 12au7.   If the grid of the 12BY7 is driven positive (from the leaky coupling cap) it will exhibit the behaviour you describe exactly.
                                             
                                            Good Luck, stay with it,
                                            KD8CN
                                            Tim 
                                             
                                          • K5MYJ
                                            My suggestion would be to disconnect the wire in the control grid pin and connect a 470K resistor from that pin to ground and see what happens to the tube. You
                                            Message 21 of 26 , Oct 23, 2013
                                              My suggestion would be to disconnect the wire in the control grid pin and connect a 470K resistor from that pin to ground and see what happens to the tube.
                                               
                                              You could also connect a current limiting resistor in series with the plate lead.
                                               
                                              Bob Macklin
                                              K5MYJ
                                              Seattle, Wa.
                                              "Real Radios Glow In The Dark"
                                              ----- Original Message -----
                                              Sent: Wednesday, October 23, 2013 9:49 AM
                                              Subject: Re: [Heathkit:Yahoo] RE: RE: TX-1 Apache Problem Brand New Member

                                               

                                              Hi Wade,
                                               If you haven't resolved this problem, yet, remove the 12by7 tube from its socket, and apply AC power to the xmtr. Check the voltage levels on each of the 9 pins, AC and DC, and report your findings to us.
                                                                                 GL & 73 de Ron
                                              From: "tjb813@..." <tjb813@...>
                                              To: heathkit@yahoogroups.com
                                              Sent: Wednesday, October 23, 2013 8:09 AM
                                              Subject: [Heathkit:Yahoo] RE: RE: TX-1 Apache Problem Brand New Member



                                              I would guess from what you describe, the coupling capacitor onthe grid of the 12BY7 is leaky.   It will measure ok when the rig is powered down, but will leak when there is plate voltage on the 12au7.   If the grid of the 12BY7 is driven positive (from the leaky coupling cap) it will exhibit the behaviour you describe exactly.
                                               
                                              Good Luck, stay with it,
                                              KD8CN
                                              Tim 


                                              ---In heathkit@yahoogroups.com, <heathkit@yahoogroups.com> wrote:

                                              There may be some oscillation or excessive levels somewhere in the audio circuit which is overdriving the 12BY7.  What is the amplitude of the audio signal at the input of the 12BY7?  Is your scope capable of displaying RF signals which may be present at the 12BY7? Try removing the 12AU7 tube which drives the 12BY7.


                                              ---In heathkit@yahoogroups.com, <tvman1954@...> wrote:

                                              I have mostly restored this TX-1. Big Iron and Lots of Plate Modulation. But Modulation is the problem. I have changed the Cathode Resistor and Cap to ground. Isolated the Input Grid with another New .01 Capacitor. Pin 9 of the 12BY7 is Grounded as it should be. B+ voltage is present on the Screen and the Plate through the Driver Transformer. I have purchased and replaced the Audio Driver Transformer Twice.
                                               
                                              On my Scope, the Input Audio Signal is Nice and Clean on Pin 2 of this 12BY7 tube. In my mind and now out of my mind, I think that everything has been done. When placed in my FT-101 the 12BY7 Tube works great so we know the tube is good.
                                               
                                              The problem is really Distorted Audio from the Secondary of the Audio Driver Transformer and also the Plate of the Tube will turn Cherry Red quite quickly.  Pin 1 the Cathode of the tube is going to over 180 volts instead of 10 volts as the Schematic references. Gentlemen, this thing has me Stumped. It is apparent that the tube is turned on hard and drawing lots of current. With 0 Volts on the Control Grid pin 2 I can&apos;t see why it wouldn&apos;t be doing that. Please Help. I have never seen a Pentode wired as a Triode much less Zero Bias on the Grid..... Help ... Help... What am I missing? Someone has surely had this problem..... Also a Brand New Member here just waiting to help others....
                                                                                                         73 from Wade/KJ4WS
                                               

                                            • k4pf@juno.com
                                              ... I agree with Tim. I missed that Wade had not checked the grid voltage, since he wrote with zero grid volts... (Apparently, he was just referring
                                              Message 22 of 26 , Oct 23, 2013
                                                > Tim KB8CN wrote
                                                > I would guess from what you describe, the coupling capacitor on the grid of the 12BY7 is leaky. It will measure ok when the rig is powered down, but will leak when there is plate voltage on the 12au7. If the grid of the 12BY7 is driven positive (from the leaky coupling cap) it will exhibit the behaviour you describe exactly.
                                                <snip>

                                                I agree with Tim. I missed that Wade had not checked the grid voltage,
                                                since he wrote "with zero grid volts..." (Apparently,
                                                he was just referring to the voltage shown on the schematic.)
                                                Also, it threw me that Wade didn't change out the coupling capacitor,
                                                when he suspected it, but only added another capacitor in series.
                                                I must learn to read more attentively.

                                                73,
                                                Ed Knobloch
                                              • kj4ws
                                                Hello to All, I Thank You All for your help so far. I have been away for a couple of days. Ron, has the theory that the 12BY7 has Grid Emission or that the
                                                Message 23 of 26 , Oct 23, 2013

                                                  Hello to All,

                                                                     I Thank You All for your help so far. I have been away for a couple of days. Ron, has the theory that the 12BY7 has Grid Emission or that the coating from the Cathode has migrated to the grid of this used tube. The original tube was a melted down, Shorted little fellow which had Fried the Modulation Driver Transformer. We have a New in Box 12BY7 from Ebay on the way. Also, the 12BY7 has a Maximum Plate Voltage Rating of 300 Volts. The Schematic calls for 370 Volts and with the raised Line Voltage of 120 volts as opposed to the 110 Volts of Days Gone By .... I am seeing about 420 VDC at the Plate of the tube. Heathkit was running the tube 70 Volts above it's Plate Rating when it was new. Now with the higher AC line voltages? I may need a Voltage Divider of some type to lower the Plate Voltage.  Once again, Thanks to you All. I will post more details after the new tube arrives. With the good tube, things may work out. Everything in the 12BY7 Circuit and the Surrounding Stages has Now been replaced.

                                                                                                                                                                      73 from Wade/KJ4WS



                                                  ---In heathkit@yahoogroups.com, <heathkit@yahoogroups.com> wrote:

                                                  > Tim KB8CN wrote
                                                  > I would guess from what you describe, the coupling capacitor on the grid of the 12BY7 is leaky. It will measure ok when the rig is powered down, but will leak when there is plate voltage on the 12au7. If the grid of the 12BY7 is driven positive (from the leaky coupling cap) it will exhibit the behaviour you describe exactly.
                                                  <snip>

                                                  I agree with Tim. I missed that Wade had not checked the grid voltage,
                                                  since he wrote "with zero grid volts..." (Apparently,
                                                  he was just referring to the voltage shown on the schematic.)
                                                  Also, it threw me that Wade didn't change out the coupling capacitor,
                                                  when he suspected it, but only added another capacitor in series.
                                                  I must learn to read more attentively.

                                                  73,
                                                  Ed Knobloch
                                                • kj4ws
                                                  Scratchy Apache CURED ! Thanks to all who helped..... After placing a New In Box and NOS 12BY7 in the Transmitter, Everything is Fine. After trying 3 separate
                                                  Message 24 of 26 , Oct 25, 2013

                                                    Scratchy Apache CURED !

                                                                                                Thanks to all who helped..... After placing a New In Box and NOS 12BY7 in the Transmitter, Everything is Fine. After trying 3 separate 12BY7 Tubes that have been in RF Service as Drivers for the FT-101 and other rigs, and watching them turn Cherry Red. It was a pure Delight to see the New Tube, work Exactly as it should. I have learned that when someone tells me that the Cathode Coating might have Migrated to the Grid ...... It is time to listen to them. The Troublesome 12BY7 Tubes all 3 work just fine at Driving Two 6146 tubes in the FT-101E ......Thank You All a Million Times for the Help.....

                                                                                                                                                         73 and May God Bless de Wade/KJ4WS

                                                                                                 



                                                    ---In heathkit@yahoogroups.com, <tvman1954@...> wrote:

                                                    Hello to All,

                                                                       I Thank You All for your help so far. I have been away for a couple of days. Ron, has the theory that the 12BY7 has Grid Emission or that the coating from the Cathode has migrated to the grid of this used tube. The original tube was a melted down, Shorted little fellow which had Fried the Modulation Driver Transformer. We have a New in Box 12BY7 from Ebay on the way. Also, the 12BY7 has a Maximum Plate Voltage Rating of 300 Volts. The Schematic calls for 370 Volts and with the raised Line Voltage of 120 volts as opposed to the 110 Volts of Days Gone By .... I am seeing about 420 VDC at the Plate of the tube. Heathkit was running the tube 70 Volts above it's Plate Rating when it was new. Now with the higher AC line voltages? I may need a Voltage Divider of some type to lower the Plate Voltage.  Once again, Thanks to you All. I will post more details after the new tube arrives. With the good tube, things may work out. Everything in the 12BY7 Circuit and the Surrounding Stages has Now been replaced.

                                                                                                                                                                        73 from Wade/KJ4WS



                                                    ---In heathkit@yahoogroups.com, <heathkit@yahoogroups.com> wrote:

                                                    > Tim KB8CN wrote
                                                    > I would guess from what you describe, the coupling capacitor on the grid of the 12BY7 is leaky. It will measure ok when the rig is powered down, but will leak when there is plate voltage on the 12au7. If the grid of the 12BY7 is driven positive (from the leaky coupling cap) it will exhibit the behaviour you describe exactly.
                                                    <snip>

                                                    I agree with Tim. I missed that Wade had not checked the grid voltage,
                                                    since he wrote "with zero grid volts..." (Apparently,
                                                    he was just referring to the voltage shown on the schematic.)
                                                    Also, it threw me that Wade didn't change out the coupling capacitor,
                                                    when he suspected it, but only added another capacitor in series.
                                                    I must learn to read more attentively.

                                                    73,
                                                    Ed Knobloch
                                                  • R M Barlow
                                                    Hi Wade,  Congrats on your success!  IMHO, you may want to check the line voltage, at your QTH, and the heater voltage, on your new 12BY7 (pin 4 or 5,
                                                    Message 25 of 26 , Oct 26, 2013
                                                      Hi Wade,
                                                       Congrats on your success!
                                                       IMHO, you may want to check the line voltage, at your QTH, and the heater voltage, on your new 12BY7 (pin 4 or 5, referenced to chassis ground).
                                                       If the line voltage is higher than ~ 115 volts (it it almost assuredly is), and/or the 12BY7 heater voltage exceeds ~ 6.8 volts, I suggest adding a variac, or a bucking xfmr, in the AC line to your xmtr (and any other vintage rigs, that you may have).
                                                       Otherwise, excessive line voltage will continue to cause premature failures of the tubes, power xfmr., and other components. A 12 volt "filament" xfmr, of adequate size, wired to buck the incoming AC line, would probably be ~ correct. 
                                                                     GL & 73 de Ron  n4gjv 

                                                      From: "tvman1954@..." <tvman1954@...>
                                                      To: heathkit@yahoogroups.com
                                                      Sent: Friday, October 25, 2013 11:59 PM
                                                      Subject: [Heathkit:Yahoo] RE: RE: RE: TX-1 Apache Problem Brand New Member



                                                      Scratchy Apache CURED !
                                                                                                  Thanks to all who helped..... After placing a New In Box and NOS 12BY7 in the Transmitter, Everything is Fine. After trying 3 separate 12BY7 Tubes that have been in RF Service as Drivers for the FT-101 and other rigs, and watching them turn Cherry Red. It was a pure Delight to see the New Tube, work Exactly as it should. I have learned that when someone tells me that the Cathode Coating might have Migrated to the Grid ...... It is time to listen to them. The Troublesome 12BY7 Tubes all 3 work just fine at Driving Two 6146 tubes in the FT-101E ......Thank You All a Million Times for the Help.....
                                                                                                                                                           73 and May God Bless de Wade/KJ4WS
                                                                                                   




                                                    • kj4ws
                                                      No one caught my mistake but, it is Killing me ..... The 12BY7 tubes are all doing a great job in the FT-101 and driving the 6JS6 tubes in the FT-101.... Not
                                                      Message 26 of 26 , Oct 28, 2013

                                                        No one caught my mistake but, it is Killing me ..... The 12BY7 tubes are all doing a great job in the FT-101 and driving the 6JS6 tubes in the FT-101.... Not 6146 tubes... Don't know where my mind was. They would go into Melt Down in the Apache TX-1 .....  Thanks Ron, The Owner of the Scratchy Apache has probably read this already. The line voltage at my QTH is 120.4 Volts most times that I check it. My friend Odie, took the Transmitter home on Sunday.. AWESOME MODULATION.... We must barely crack the Microphone Gain Open to get Great Audio from the Rig......

                                                                                                                         73 de Wade/KJ4WS



                                                        ---In heathkit@yahoogroups.com, <heathkit@yahoogroups.com> wrote:

                                                        Hi Wade,
                                                         Congrats on your success!
                                                         IMHO, you may want to check the line voltage, at your QTH, and the heater voltage, on your new 12BY7 (pin 4 or 5, referenced to chassis ground).
                                                         If the line voltage is higher than ~ 115 volts (it it almost assuredly is), and/or the 12BY7 heater voltage exceeds ~ 6.8 volts, I suggest adding a variac, or a bucking xfmr, in the AC line to your xmtr (and any other vintage rigs, that you may have).
                                                         Otherwise, excessive line voltage will continue to cause premature failures of the tubes, power xfmr., and other components. A 12 volt "filament" xfmr, of adequate size, wired to buck the incoming AC line, would probably be ~ correct. 
                                                                       GL & 73 de Ron  n4gjv 

                                                        From: "tvman1954@..." <tvman1954@...>
                                                        To: heathkit@yahoogroups.com
                                                        Sent: Friday, October 25, 2013 11:59 PM
                                                        Subject: [Heathkit:Yahoo] RE: RE: RE: TX-1 Apache Problem Brand New Member



                                                        Scratchy Apache CURED !
                                                                                                    Thanks to all who helped..... After placing a New In Box and NOS 12BY7 in the Transmitter, Everything is Fine. After trying 3 separate 12BY7 Tubes that have been in RF Service as Drivers for the FT-101 and other rigs, and watching them turn Cherry Red. It was a pure Delight to see the New Tube, work Exactly as it should. I have learned that when someone tells me that the Cathode Coating might have Migrated to the Grid ...... It is time to listen to them. The Troublesome 12BY7 Tubes all 3 work just fine at Driving Two 6146 tubes in the FT-101E ......Thank You All a Million Times for the Help.....
                                                                                                                                                             73 and May God Bless de Wade/KJ4WS
                                                                                                     


                                                        ---In heathkit@yahoogroups.com, <tvman1954@...> wrote:

                                                        Hello to All,
                                                                           I Thank You All for your help so far. I have been away for a couple of days. Ron, has the theory that the 12BY7 has Grid Emission or that the coating from the Cathode has migrated to the grid of this used tube. The original tube was a melted down, Shorted little fellow which had Fried the Modulation Driver Transformer. We have a New in Box 12BY7 from Ebay on the way. Also, the 12BY7 has a Maximum Plate Voltage Rating of 300 Volts. The Schematic calls for 370 Volts and with the raised Line Voltage of 120 volts as opposed to the 110 Volts of Days Gone By .... I am seeing about 420 VDC at the Plate of the tube. Heathkit was running the tube 70 Volts above it&apos;s Plate Rating when it was new. Now with the higher AC line voltages? I may need a Voltage Divider of some type to lower the Plate Voltage.  Once again, Thanks to you All. I will post more details after the new tube arrives. With the good tube, things may work out. Everything in the 12BY7 Circuit and the Surrounding Stages has Now been replaced.
                                                                                                                                                                            73 from Wade/KJ4WS


                                                        ---In heathkit@yahoogroups.com, <heathkit@yahoogroups.com> wrote:

                                                        > Tim KB8CN wrote
                                                        > I would guess from what you describe, the coupling capacitor on the grid of the 12BY7 is leaky. It will measure ok when the rig is powered down, but will leak when there is plate voltage on the 12au7. If the grid of the 12BY7 is driven positive (from the leaky coupling cap) it will exhibit the behaviour you describe exactly.
                                                        <snip>

                                                        I agree with Tim. I missed that Wade had not checked the grid voltage,
                                                        since he wrote "with zero grid volts..." (Apparently,
                                                        he was just referring to the voltage shown on the schematic.)
                                                        Also, it threw me that Wade didn&apos;t change out the coupling capacitor,
                                                        when he suspected it, but only added another capacitor in series.
                                                        I must learn to read more attentively.

                                                        73,
                                                        Ed Knobloch




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