Henry 2KD-5 high voltage problems

Discussion in 'Amateur Radio Amplifiers' started by W5VQ, Jun 26, 2020.

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  1. W5VQ

    W5VQ Premium Subscriber QRZ Page

    Back in January this year a friend gave me a very nice looking Henry 2KD-5 amp. He had just received his KPA-1500 and didn’t want the Henry. He also told me the amp had high voltage issues, it was fine on the CW position (2400vdc), but on SSB position (3400vdc) it had arc in the power supply somewhere. I got it home on the bench and sure enough, no problem on the low voltage tap, but on the high tap after a while you could hear it snap like breaking a wooden pencil. I decided to completely rebuild the power supply. New capacitors, equalizer resistors, new phenolic board, rectifiers checked OK, transformer megged with a Biddle megger check OK. Reassembled and on initial startup looked good, 2400vdc on CW, 3400vdc on SSB using a Fluke 87 & HV probe NO short NO “snap”. Problem solved? NO under normal load 700ma plate current and about 1250 watts out on the SSB position it shorts and pops just like before. I have tried to see the flash with all the lights off, but can’t see where it’s coming from. Sounds like in the same place as before the back of the capacitor/resistor bank. Anyone out there have any suggestions or ideas? Any help would be appreciated.
     

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  2. W1QJ

    W1QJ Ham Member QRZ Page

    I rebuilt a couple of those power supplies before but I never do it the same way. I modernize it. As I recall the high voltage passageway is terrible on that amp. It runs close and if that HV wire is broken down over time I wouldn’t doubt it arcs over someplace.
     
    KU3X likes this.
  3. W5VQ

    W5VQ Premium Subscriber QRZ Page

    Yes it is very close in there, I really don't like the HV cables in the wiring harness that runs along the bottom rail.
    Guess I will unlace the cables and check that.
     
  4. WC5P

    WC5P Platinum Subscriber Platinum Subscriber QRZ Page

    Running the HV lead through a piece of teflon tubing might resolve the problem. 4mm or 6mm id available on Amazon.
     
    AC0OB and K4AGO like this.
  5. W5VQ

    W5VQ Premium Subscriber QRZ Page

    I will keep that in mind. There are 3 HV cables that go to the CW/SSB switch on the front, I suspect that's were the problem is.
     
  6. WC5P

    WC5P Platinum Subscriber Platinum Subscriber QRZ Page

    You think the problem may be in the switch? Interesting. I had a 2KD-5 years ago. Called it Ol’ Hank. Heck of a strong amp. I don’t remember too much else about it except that it wasn’t much fun to work on, and the relay was loud. I remember that I had to replace the on-off switches, which are actually very expensive circuit breakers in disguise.
     
  7. W1QJ

    W1QJ Ham Member QRZ Page

    What line voltage are you using to power this amplifier? 120 or 240? I just want to point out that there is a MAJOR flaw in the line voltage diagram. The TWO MAJOR flaws depends on which vintage model you have. They have the wiring all screwed up and the color code they use in the diagram for their intended purpose is against all common color code standards. Not that this is your problem, but you should be totally aware that their way of hooking the amp up for 240v is wrong and should be noted and changed.
     
  8. W5VQ

    W5VQ Premium Subscriber QRZ Page

    This one is wired for 240vac. I will look at the primary wiring and make the changes if needed. Thanks for the heads up.
     
  9. KC3HUM

    KC3HUM Ham Member QRZ Page

    Just in case this could help ( I realize this is part of the rf and not high voltage), BBI on you tube who has a few vids on the Henry 2k4 amps, mentioned in a video of arcing problems he had a bit of a hard time finding where it was coming from. He found the arcing within one of the all threads assembling the air variable capacitors together. He had to replace one of the 4 all threads and clean up the surfaces for better contact.

    I like the idea suggesting teflon sleeve, but Id rather replace the high voltage line all together. I'm planning on doing that with my 2k-4.
     
  10. W5VQ

    W5VQ Premium Subscriber QRZ Page

    I saw the you tube BBI did when I was doing some research on the 2KD-5, it was interesting. My RF deck is in good shape no arcing there. I plan to check all the HV cables and will probably change them out and re-route them.
     

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