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Re: SG230 RF sensing diode problem

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  • Michael Kendall
    Hello group,     This is the thread related to the diode problem and the case number on the diodes.  It doesn t get good until page 2 or 3 from my
    Message 1 of 5 , Apr 4, 2012
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      Hello group,
       
        This is the thread related to the diode problem and the case number on the diodes.  It doesn't get good until page 2 or 3 from my reading.  Cecil Moore weighed in on it and he is a HAM's Ham in my book.
        Here is the link on the bleeders.  It is not geared towards SG-230's but instead towards antennas in general.  Personally, I would put the bleeder on the input network of the SG-230 to reduce current accross the bleeder (high resistance with less voltage across the bleeder means less current) instead of at the antenna.  There is room in the coupler to put it across the input coax.  The DC path is essentially a short to the antenna in any tune position or during any changing of relays in the SG-230.  It is not a DC path to the counterpoise as there are three parallel high value caps and a resistor from the circuit board ground to the counterpoise.  The bleeder resistor should work from the hot side of the coax on the input side to the circuit board ground.
       
       
        I will be putting the bleeder on the input as well as the better diode on my modified "supersized" and balanced SG-230's that I'm working on.
       
      73,
      Mike


      --- On Tue, 4/3/12, Michael Kendall <michael.kendall@...> wrote:

      From: Michael Kendall <michael.kendall@...>
      Subject: SG230 RF sensing diode problem
      To: smartuners@yahoogroups.com
      Date: Tuesday, April 3, 2012, 7:57 PM

      Hello group,
       
        I read a very detailed message thread on the radiobanter thread regarding the SMD's blowing on the newer boards.  From the case code they were able to determine it was an MMDB914 and not an MMBD4148.  Both of those have less ratings than the origional 1N4148.  Phil, AD5X, recommended a good diode that is used as a switching diode up to frequencies alot higher than HF work.  It is the BAV21 (in a leaded case) and in the exact same case with the exact same anode/cathode case style as what is in the SG230 it is the BAS21.  Here is the spec sheet,
       highly recommend use of this and also one of Phil's high wattage/high ohmage bleeder resistors or two in series in your coupler as well to protect the RF sensing circuitry.
        I can provide the part number for the bleeder if necessary also in a different email.  I'm buying me some of those diodes!
       
      Best regards,
      Mike
       
    • Michael
      Recommend putting the bleeder on the output of the network. The input of the network is already a low impedence path to ground, verified that with my
      Message 2 of 5 , Apr 7, 2012
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        Recommend putting the bleeder on the output of the network. The input of the network is already a low impedence path to ground, verified that with my multimeter last night. With no power applied to the coupler there was an open from the RF input to the RF output so the bleeder would need to go on the output of the coupler to ground to ensure when the tuner is energized there is no possibility of static reaching anywhere in the circuit.
        73,
        Mike


        --- In Smartuners@yahoogroups.com, Michael Kendall <michael.kendall@...> wrote:
        >
        > Hello group,
        >  
        >   This is the thread related to the diode problem and the case number on the diodes.  It doesn't get good until page 2 or 3 from my reading.  Cecil Moore weighed in on it and he is a HAM's Ham in my book.
        > http://www.radiobanter.com/showthread.php?t=132784
        >   Here is the link on the bleeders.  It is not geared towards SG-230's but instead towards antennas in general.  Personally, I would put the bleeder on the input network of the SG-230 to reduce current accross the bleeder (high resistance with less voltage across the bleeder means less current) instead of at the antenna.  There is room in the coupler to put it across the input coax.  The DC path is essentially a short to the antenna in any tune position or during any changing of relays in the SG-230.  It is not a DC path to the counterpoise as there are three parallel high value caps and a resistor from the circuit board ground to the counterpoise.  The bleeder resistor should work from the hot side of the coax on the input side to the circuit board ground.
        > http://www.ad5x.com/images/Articles/Static%20Bleed.pdf
        >  
        > http://www.mouser.com/ProductDetail/Ohmite/MOX-1-123004F/?qs=r4Z5oksfPX0%252bxaVVECEGrA%3d%3d
        >  
        >   I will be putting the bleeder on the input as well as the better diode on my modified "supersized" and balanced SG-230's that I'm working on.
        >  
        > 73,
        > Mike
        >
        >
        > --- On Tue, 4/3/12, Michael Kendall <michael.kendall@...> wrote:
        >
        >
        > From: Michael Kendall <michael.kendall@...>
        > Subject: SG230 RF sensing diode problem
        > To: smartuners@yahoogroups.com
        > Date: Tuesday, April 3, 2012, 7:57 PM
        >
        >
        >
        >
        >
        >
        >
        > Hello group,
        >  
        >   I read a very detailed message thread on the radiobanter thread regarding the SMD's blowing on the newer boards.  From the case code they were able to determine it was an MMDB914 and not an MMBD4148.  Both of those have less ratings than the origional 1N4148.  Phil, AD5X, recommended a good diode that is used as a switching diode up to frequencies alot higher than HF work.  It is the BAV21 (in a leaded case) and in the exact same case with the exact same anode/cathode case style as what is in the SG230 it is the BAS21.  Here is the spec sheet,
        > http://www.fairchildsemi.com/ds/BA/BAS21.pdf
        >  highly recommend use of this and also one of Phil's high wattage/high ohmage bleeder resistors or two in series in your coupler as well to protect the RF sensing circuitry.
        >   I can provide the part number for the bleeder if necessary also in a different email.  I'm buying me some of those diodes!
        >  
        > Best regards,
        > Mike
        >  
        >
      • Christopher Brown
        This does not sound right, there should always be a DC connection from RF in to RF out. Powered off, one with all inductors inline. Powered on, with all
        Message 3 of 5 , Apr 7, 2012
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          This does not sound right, there should always be a DC connection from
          RF in to RF out.

          Powered off, one with all inductors inline.

          Powered on, with all inductors switched out.

          The RF input is also grounded via the sense transformer.


          Did you perhaps check between coax shield and RF GND? These are not DC
          coupled.



          All that aside, I am in the habit of putting bleeders all over the
          place, keep boxes of 10k, 100k and 1M 2w 1kv or better rated around.

          Generally throw a 100k center to ground on the antenna jack of any radio
          I open. AMPs, tuners, etc the same. Unless DC grounded by default (by
          something larger than a sense transformer).

          On both 237s and the 235 I threw in a 100k on input and a 1M on output.

          We get long dry winters with dry powder snow and high winds. Had radio
          damaged my first year as a HAM, would have taken be off the air for 6
          months if not for some help (and spare parts) donated to the cause.

          On 4/7/12 4:44 AM, Michael wrote:
          > Recommend putting the bleeder on the output of the network. The
          > input of the network is already a low impedence path to ground,
          > verified that with my multimeter last night. With no power applied to
          > the coupler there was an open from the RF input to the RF output so
          > the bleeder would need to go on the output of the coupler to ground
          > to ensure when the tuner is energized there is no possibility of
          > static reaching anywhere in the circuit. 73, Mike
          >
          >
          > --- In Smartuners@yahoogroups.com, Michael Kendall
          > <michael.kendall@...> wrote:
          >>
          >> Hello group,
          >>
          >> This is the thread related to the diode problem and the case number
          >> on the diodes. It doesn't get good until page 2 or 3 from my
          >> reading. Cecil Moore weighed in on it and he is a HAM's Ham in my
          >> book. http://www.radiobanter.com/showthread.php?t=132784 Here is
          >> the link on the bleeders. It is not geared towards SG-230's but
          >> instead towards antennas in general. Personally, I would put the
          >> bleeder on the input network of the SG-230 to reduce current
          >> accross the bleeder (high resistance with less voltage across the
          >> bleeder means less current) instead of at the antenna. There is
          >> room in the coupler to put it across the input coax. The DC path
          >> is essentially a short to the antenna in any tune position or
          >> during any changing of relays in the SG-230. It is not a DC path
          >> to the counterpoise as there are three parallel high value caps and
          >> a resistor from the circuit board ground to the counterpoise. The
          >> bleeder resistor should work from the hot side of the coax on the
          >> input side to the circuit board ground.
          >> http://www.ad5x.com/images/Articles/Static%20Bleed.pdf
          >>
          >> http://www.mouser.com/ProductDetail/Ohmite/MOX-1-123004F/?qs=r4Z5oksfPX0%252bxaVVECEGrA%3d%3d
          >>
          >> I will be putting the bleeder on the input as well as the better
          >> diode on my modified "supersized" and balanced SG-230's that I'm
          >> working on.
          >>
          >> 73, Mike
          >>
          >>
          >> --- On Tue, 4/3/12, Michael Kendall <michael.kendall@...> wrote:
          >>
          >>
          >> From: Michael Kendall <michael.kendall@...> Subject: SG230 RF
          >> sensing diode problem To: smartuners@yahoogroups.com Date: Tuesday,
          >> April 3, 2012, 7:57 PM
          >>
          >>
          >>
          >>
          >>
          >>
          >>
          >> Hello group,
          >>
          >> I read a very detailed message thread on the radiobanter thread
          >> regarding the SMD's blowing on the newer boards. From the case
          >> code they were able to determine it was an MMDB914 and not an
          >> MMBD4148. Both of those have less ratings than the origional
          >> 1N4148. Phil, AD5X, recommended a good diode that is used as a
          >> switching diode up to frequencies alot higher than HF work. It is
          >> the BAV21 (in a leaded case) and in the exact same case with the
          >> exact same anode/cathode case style as what is in the SG230 it is
          >> the BAS21. Here is the spec sheet,
          >> http://www.fairchildsemi.com/ds/BA/BAS21.pdf highly recommend use
          >> of this and also one of Phil's high wattage/high ohmage bleeder
          >> resistors or two in series in your coupler as well to protect the
          >> RF sensing circuitry. I can provide the part number for the bleeder
          >> if necessary also in a different email. I'm buying me some of
          >> those diodes!
          >>
          >> Best regards, Mike
          >>
          >>
          >
          >
          >
          >
          > ------------------------------------
          >
          > Yahoo! Groups Links
          >
        • Michael
          I have two new SG-230 s that I m modifying. I mistakenly measured on the one that I am prepping for modification and did a measurement on the other one that
          Message 4 of 5 , Apr 8, 2012
          • 0 Attachment
            I have two new SG-230's that I'm modifying. I mistakenly measured on the one that I am prepping for modification and did a measurement on the other one that read the resistance of the transformer primary in the RF sensing network.
            I still would never leave those stock diodes in there and go with the BAS-21's. Something is blowing those diodes in some cases. I emailed Steve who was recommended for repairs off the Eham.net reviews. He told me that the diodes are his most common failure item.
            73,
            Mike


            --- In Smartuners@yahoogroups.com, "Michael" <michael.kendall@...> wrote:
            >
            > Recommend putting the bleeder on the output of the network. The input of the network is already a low impedence path to ground, verified that with my multimeter last night. With no power applied to the coupler there was an open from the RF input to the RF output so the bleeder would need to go on the output of the coupler to ground to ensure when the tuner is energized there is no possibility of static reaching anywhere in the circuit.
            > 73,
            > Mike
            >
            >
            > --- In Smartuners@yahoogroups.com, Michael Kendall <michael.kendall@> wrote:
            > >
            > > Hello group,
            > >  
            > >   This is the thread related to the diode problem and the case number on the diodes.  It doesn't get good until page 2 or 3 from my reading.  Cecil Moore weighed in on it and he is a HAM's Ham in my book.
            > > http://www.radiobanter.com/showthread.php?t=132784
            > >   Here is the link on the bleeders.  It is not geared towards SG-230's but instead towards antennas in general.  Personally, I would put the bleeder on the input network of the SG-230 to reduce current accross the bleeder (high resistance with less voltage across the bleeder means less current) instead of at the antenna.  There is room in the coupler to put it across the input coax.  The DC path is essentially a short to the antenna in any tune position or during any changing of relays in the SG-230.  It is not a DC path to the counterpoise as there are three parallel high value caps and a resistor from the circuit board ground to the counterpoise.  The bleeder resistor should work from the hot side of the coax on the input side to the circuit board ground.
            > > http://www.ad5x.com/images/Articles/Static%20Bleed.pdf
            > >  
            > > http://www.mouser.com/ProductDetail/Ohmite/MOX-1-123004F/?qs=r4Z5oksfPX0%252bxaVVECEGrA%3d%3d
            > >  
            > >   I will be putting the bleeder on the input as well as the better diode on my modified "supersized" and balanced SG-230's that I'm working on.
            > >  
            > > 73,
            > > Mike
            > >
            > >
            > > --- On Tue, 4/3/12, Michael Kendall <michael.kendall@> wrote:
            > >
            > >
            > > From: Michael Kendall <michael.kendall@>
            > > Subject: SG230 RF sensing diode problem
            > > To: smartuners@yahoogroups.com
            > > Date: Tuesday, April 3, 2012, 7:57 PM
            > >
            > >
            > >
            > >
            > >
            > >
            > >
            > > Hello group,
            > >  
            > >   I read a very detailed message thread on the radiobanter thread regarding the SMD's blowing on the newer boards.  From the case code they were able to determine it was an MMDB914 and not an MMBD4148.  Both of those have less ratings than the origional 1N4148.  Phil, AD5X, recommended a good diode that is used as a switching diode up to frequencies alot higher than HF work.  It is the BAV21 (in a leaded case) and in the exact same case with the exact same anode/cathode case style as what is in the SG230 it is the BAS21.  Here is the spec sheet,
            > > http://www.fairchildsemi.com/ds/BA/BAS21.pdf
            > >  highly recommend use of this and also one of Phil's high wattage/high ohmage bleeder resistors or two in series in your coupler as well to protect the RF sensing circuitry.
            > >   I can provide the part number for the bleeder if necessary also in a different email.  I'm buying me some of those diodes!
            > >  
            > > Best regards,
            > > Mike
            > >  
            > >
            >
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