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31583Re: [Heathkit:Yahoo] TX-1 Apache Problem Brand New Member

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  • Howie
    Oct 18, 2013
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      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

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