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BTI amplifier

Discussion in 'Amateur Radio Amplifiers' started by N2ZD, Nov 24, 2019.

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  1. N2ZD

    N2ZD Ham Member QRZ Page

    It shows about 3k plate voltage give or take. Once again it’s idling on 110v. At least this amp doesn’t trip my breaker like the BTI lol
     
  2. W1QJ

    W1QJ Ham Member QRZ Page

    Maybe your antenna relay is stuck in xmit or the circuit is energized and the amp is in transmit.
     
  3. N2ZD

    N2ZD Ham Member QRZ Page

    I checked the relay (RLY-1) and it’s open. I’ll get a better look at it and clean it up. I have extra tubes but both tubes in there now are glowing (I know Murphy’s law :)
    To me, it appears to have lost cutoff bias or it’s in TX as well.
    Before guessing , I’ll go thru the whole thing. I appreciate your help and guidance.
     
    Last edited: Dec 2, 2019
  4. W1QJ

    W1QJ Ham Member QRZ Page

    It is easy to tell if it is in transmit. Does it have a transmit light that lights up in transmit? If that light is off and the tubes draw current then it is a cut off bias problem. Could be bad connection on relay or something in the circuit. I would have to check the schematic. Make sure there is no wire in the antenna relay jack.
     
  5. N2ZD

    N2ZD Ham Member QRZ Page

    I don’t think this amp has a TX light. There’s nothing in
    Henry’s 2k-4 manual from what I can see about such a thing and I’ve Been going over it As you wrote your reply, I was going over the manual and the relay I mentioned is the antenna relay and it’s not energized when this occurs, I “chicken sticked” the relay and no change when closed.
     
  6. W1QJ

    W1QJ Ham Member QRZ Page

    UGH... I checked the schematic. Very unconventional circuitry for a 3-500 based amplifier. The grids are floating and the grid current is measured at the grids.
     
  7. W1QJ

    W1QJ Ham Member QRZ Page

    Well, if C58 is bad it could cause this problem. You could easily eliminate C58 temporarily to see if the problem goes away.
     
  8. N2ZD

    N2ZD Ham Member QRZ Page

    It shows no grid current btw.

    After exercising the relay, the plate current dropped and the tubes cherry very little , if at all.
     

    Attached Files:

  9. W1QJ

    W1QJ Ham Member QRZ Page

    There should be ZERO plate current in stand by. I see the current went down some but there still appears to be some plate current flowing.
     
  10. N2ZD

    N2ZD Ham Member QRZ Page

    The manual states resting current should be between 150-200 ma

    This thing is showing 140 ma now.
    I’m guessing running unconventional, it draws some current.
     

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