Mint Henry 2K Classic amplifier bring up questions.

Discussion in 'Amateur Radio Amplifiers' started by N9EVD, Nov 7, 2019 at 2:50 PM.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    If the anode connector isn't on the tube, it doesn't have any HV. Zero risk, except to you if you happen to contact the HV. Don't do that! Also remember all the Henry amps I've ever worked on have a protection system that won't allow you to turn them on if the covers are removed to allow access to the tubes. You have to defeat that interlock to get it to power on at all, even the filaments.
    I think if you use an Ohmmeter to test continuity between the neutral and the chassis, you'll find they really are connected internally. The only time they wouldn't be is with a 4-wire system where neutral and ground are two separate conductors.
     
  2. N9EVD

    N9EVD Ham Member QRZ Page

    Thank you for that info. When I was referring to risking the amplifier HV supply, and the tube suddenly gassing up while operating, I was referring to actual operation with the HV connected.

    And this amp has a 4 conductor power wire on it, but the green, GND wire is connected internally to the Chassis GND but the wire is not connected to anything on the plug end. The plug is has 3 contacts that are connected to neutral, and the 2-220v taps.
     
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Oh, for actual operation with a tube that goes gassy, the Henry amps have two levels of protection: Usually a 1.5A cathode fuse (replaceable) and two AC line fuses or a double-pole circuit breaker, depending on the model. They protect the whole amplifier.

    With a 4-wire power cord, tie the neutral and ground together at the plug. Some had that, some didn't.

    Do you have the manual?
     
  4. N9EVD

    N9EVD Ham Member QRZ Page

    Yes, it did come with the manual.
     
  5. N8FVJ

    N8FVJ Ham Member QRZ Page

    There is no risk to the amp with a filament failure and no high voltage on the tube anodes.
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    There's very little risk even with the HV connected if a tube arcs internally due to lack of vacuum.

    Usually that would just blow the 1.5A cathode fuse very fast, which opens the HV circuit.

    3-500Zs have failed by the millions (? -- well, certainly thousands, anyway) over the past 50 years and in well-designed amps nothing bad results. The Henry has protective circuits and the power supply is very robust.
     
  7. N8FVJ

    N8FVJ Ham Member QRZ Page

    Eimac made some leaky 3-500Z tubes in I believe the late 1980s. If the tubes are bad, RF Parts sells a very good Chinese 3-500Z.
     
  8. N9EVD

    N9EVD Ham Member QRZ Page

    OK, because ground and neutral are not connected together internal to the amp, I will connect ground and neutral together at the 3 prong 220 volt plug.
     
  9. N9EVD

    N9EVD Ham Member QRZ Page

    Some images of the outside of the amp.
     

    Attached Files:

  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That's what they all looked like!

    Did you fire it up yet?

    Note the 1.5A fuse at the rear panel; that's the cathode fuse that protects the power supply and the stuff between the power supply and the tubes in the event of a tube arc or short.
     

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