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Henry 2K-D relay woes

Discussion in 'Amateur Radio Amplifiers' started by AD0AC, Nov 15, 2015.

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  1. AD0AC

    AD0AC Ham Member QRZ Page

    Continuing the following thread:

    I pulled the T/R relay today and tested it. The relay slightly pulls down, but not enough to make contact on the N/O side. The coil is badly corroded under the tape and I think it's just too weak to pull in. Might be burned up, who knows. The relay was also made by Kurman, not Magnacraft, and seems equally unobtanium.

    I've reviewed the Guardian relay kit produced by Henry and $140 seems a bit steep for two $10 relays. It appears that one relay is assigned for input RF switching and the other for output. I'd like to figure out how it's wired up and put one together myself, or use one 3PDT replacement relay. I'm concerned that having two relays replace one may cause issues with delayed switching, so my inclination is to use one relay. There is also not much room in the first-gen 2K-D cabinet.

    At some point, this amp was set up to use 3-500z tubes, but there is no bias zener present. Any ideas on where to put one? Any relay replacement recommendations?

    Attached Files:

  2. W9GB

    W9GB Ham Member QRZ Page

    Relay could have been changed earlier, or may have been substitute. You are dealing with a 40+ year old HF amplifier design and build.

    Henry Radio is no longer in Butler, MO ... and proper advice (FREE, volunteers that receive no compensation) was given the first time you asked. You don't want to see my professional consulting rates.

    Those kits for EASY installation were designed and offered a number of years ago. They won't be around forever, so that it is "an easy relay change".

    At this point, spending over 12 months on this project,
    you seem to need an Elmer (or finances to finish) ---- see if KC5RT (Liberty, MO) has time to assist.

    Previous Henry Restoration by KC5RT 2K.htm
    Last edited: Nov 15, 2015
  3. AD0AC

    AD0AC Ham Member QRZ Page

    Indeed, and I appreciate the advice. Part of the problem is that Henry does not offer any support for the older amps (yes, I asked), and many other resources have disappeared from the Internet, such as the NE7X website. I have reached out to KC5RT and reviewed his restoration, which was helpful in restoring the LV supply.

    At this point, I just want to know whether it's better to use two DPDT relays, or one 3PDT relay to replace the original TR relay. The original Henry schematics for this amp are laughably inaccurate and the parts list actually describes the relay as a DPDT rather than a 3PDT.
  4. W1QJ

    W1QJ Ham Member QRZ Page

    Should be very simple to use a generic 3pdt relay. no magic here. There is a bias didode or should be, but it does not look like a typical zener. It looks like a block rectifier diode instead.
  5. AD0AC

    AD0AC Ham Member QRZ Page

    Thanks, Louis, I was hoping you would chime in. The project has also overlapped with a job change and birth of a child, so the amp has been sitting in the corner of the basement for a while. I just got around to disassembling the RF deck again today to get the relay out. Tomorrow I will test the relays in the power supply to see if one or both have similar problems.
  6. AD0AC

    AD0AC Ham Member QRZ Page

    Sure enough, one of the open frame relays in the power supply isn't making contact on two of its three contacts either. The two relays in the power supply are identical to the TR relay, same mfg and layout. I might as well replace all three with modern general purpose relays.
  7. W1QJ

    W1QJ Ham Member QRZ Page

    YUP that is what I would do.
  8. AD0AC

    AD0AC Ham Member QRZ Page

    Okie dokie!

    We're making some progress. I ordered three new relays back in December, one for the T/R and two for the power supply. You can see the old T/R relay I pulled out next to one of the new relays:


    To get to the old relay, I had to remove all of the rear panel connectors and the mounting plate for the whole circuit. Compared to what I've seen from pictures of later 2k models, this was a pretty good teardown:


    The original relay had a special mounting bracket that didn't match up at all with the new relay, so I made a new one out of Lexan. The new relay is a tight fit:


    The insulation on the thicker wires had become brittle over time, so I had to rewire much of the output circuit and extend several wires to meet the business end of the new relay:


    New input and output jacks were installed, but the old filter bypass cap on the HV line broke off from stress, so I'm at a stopping point again. There's a hamfest tomorrow and hopefully I'll find one there, otherwise it'll be a few days waiting on Mouser:


  9. AD0AC

    AD0AC Ham Member QRZ Page

    In the meantime, here is a picture of the top side of the power supply. The other two open frame relays are in the lower right hand corner. Right now the plan is to button up the RF deck and test the relay operation with no RF power or tubes installed, then tackle the other two relays. I know progress has been extremely slow, but that's the reality of 80 hour work weeks all winter and springtime!

    Interesting thing about the power supply. The serial number on the amp suggests an assembly date of somewhere in 1962. The power supply has a small blower on top of either the HV choke or transformer that blows onto the bleeders with a date of 1980. The original 3B28 tubes were also replaced with diode stacks at some point. I need to test those because the HV only seemed to come up around 2-2500 last time I checked.


    The PS is pretty filthy too. It was sitting under a workbench in the previous owners garage for some time. I managed to blow out most of the dust, but I need to really get back in there before I fire it up again.
  10. WD8ED

    WD8ED Ham Member QRZ Page

    while not exactly the same, but very similar... I recently completed a 2KD5 conversion to a W7RY Bias and QSK relay driver. I used two Gigavac GH-1 relays for antenna switching. You must use two due to the way the relays are wired. It is possible to rewire the amp to more common method in order to use a smaller DPDT input relay. But the relative output meter would have to be reconfigured or eliminated. With the W7RY bias board almost all of the bias circuit components and some wiring can be eliminated and converted to solid state switching. I retained the bias fuse in the front panel. The board is cheap. The relays no so much, but can be had cheaper found used. I used two brand new ones. That expensive bias diode is now gone along with a couple resistors. The amp is now fully QSK capable, totally quiet and has adjustable bias. The low voltage transformer output taps directly into the bias board. It then supplies all other relay, keying and bias voltages. I used the W7RY board for Ameritron AL-82.

    I loved my Henry, but now I really love it. I only wish it had 160m in it. I have researched that and it's possible, but no small chore!

    I did take some pictures of the install, but not enough to consider a tutorial or webpage. I can post them if there's any interest. I just finished it a week ago so a write up would still be fresh in my head!



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