Mint Henry 2K Classic amplifier bring up questions.

Discussion in 'Amateur Radio Amplifiers' started by N9EVD, Nov 7, 2019.

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  1. N9EVD

    N9EVD Ham Member QRZ Page

    BCFB2E00-85D9-4552-8AF6-85ACD9F626C9.jpeg 09E432DB-0F16-4B7E-A0D8-EC46D75901D6.jpeg F6A0EA8A-E5FC-4E45-902C-0E05FED8526C.jpeg I purchased a Henry 2K Classic from a ham friend that was moving and scaling down. This amp has been sitting for a while but is very clean. I have had it for a couple of years, but I have not fired it up yet.

    I removed the tubes to check them out and they are very nice Eimac 3-500z tubes showing very little or at least very gentle use. One of the tubes that litter my looks to be almost unused has what looks like a small internal fracture. I was considering removing the anode power on the tubes to do a gas test on the tubes to make sure the tube is still maintaining a vacuum. Is this tube safe to use? Is it more likely to fail and possibly damage the amp? See attached images. The glass on the outside looks to be intact and feels smooth. If the gas test does not reveal an issue, Is it safe to use this tube? Any recommendations would be appreciated.
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The tube you show was manufactured in early 1987 so it's more than 32 years old.

    How do you vacuum test the tube? Just apply filament power and see if it burns up? Maybe that works, never tried it.

    I'd be highly suspicious of that tube.
     
  3. N9EVD

    N9EVD Ham Member QRZ Page

    What I have read is to disconnect the anode so there is no high voltage on the anode and turn the amp on. This only applies the filament voltage. If the tube has a lot of gas, then the interior of the tube should almost immediately turn white.
     
  4. N9EVD

    N9EVD Ham Member QRZ Page

    I assume this prevents a potential short from damaging the HV supply.
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That may well work fine (never tried it).

    In any case, it shouldn't hurt the tube (if it's good) and shouldn't hurt the amp in any way.

    Why not try that and see what happens?
     
  6. N8FVJ

    N8FVJ Ham Member QRZ Page

    Install tubes with anode caps removed. Turn on the amp. A very gassy tube will have the filament start burn (oxidize) and produce a light foggy appearance inside the gas. No vacuum will have the filament burn out in about 15-30 seconds. If no issues noted after about 30 minutes filament voltage applied, apply high voltage. Careful, anode caps may have high voltage. Short to ground with insulated screwdriver first before installing anode caps to the tubes. If still good (no issues) try driving the amp for RF output.
     
  7. K3XR

    K3XR Ham Member QRZ Page

    Bears repeating, if you have never worked with high power tube amps before, or even if you have, use caution there are deadly voltages present.

    Henry amps are first class have owned a couple over the years. Quality all the way.
     
  8. N9EVD

    N9EVD Ham Member QRZ Page

    N8FVJ, Thanks for the input, and yes I will be more than careful with the inside of the amp. My training has always taught me to assume High voltage is always present, even after you have confirmed that the voltage has been eliminated. I have a 40K probe that I use to confirm that no voltage is present before going any further. Even after this, I remove all metal from my hands, rings, etc. and assume some voltage is still present. But thank you for the reminders, it may save a life someday.
     
  9. N9EVD

    N9EVD Ham Member QRZ Page

    Thank you for the reminder, will use all the caution, grounding, confirmation of no voltage present, etc.
     
    K3XR likes this.
  10. N9EVD

    N9EVD Ham Member QRZ Page

    So, my first question is, am I risking the amplifier by after passing the gas test, using a tube that shows an internal fracture? If the tube gasses up all the sudden, arcs would likely occur if HV is present and the HV supply is at risk. Just guessing.

    Also, for testing purposes I have a 3 prong 220 plug attached. Neutral, plus 2x hot wires. Chassis ground is not connected to anything on the plug. Is this an issue for testing?
     

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