3-500Z gassing?

Discussion in 'Amateur Radio Amplifiers' started by K6BSU, Feb 3, 2018.

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  1. K9DNH

    K9DNH Ham Member QRZ Page

    De-Gassing??.. Here is a site that has a pretty good discussion about tube "reconditioning"
    pa0fri.com that is pa(zero)fri.com
    I had a half dozen 4-400 that came from various sources. I built a rig just like he describes. When I checked them, they all showed various degree's of gassing or needing something before I used them. So I did it to all of them and they came out all about even. I am getting ready to do about a dozen 813's next. the reason for my concern is, I read an article once about a someone who bought a couple of 304TL's and was going to build a gg linear. A third party who I don't remember told him "those old tubes will pop soon after you put high voltage too them". I thought about that and then forgot about it because I wasn't building a 304TL amp. I do remember a friend of mine running a single one in GG back when we were kids. He had no problem with it with a few hundred volts on it. They were plentiful then on the surplus market for 2 or 3 dollars. So 60 years fast forward and I got a pristine Johnson Thunderbolt. I haven't fired it up yet, but I just wanted to take precautions to preserve these old tubes that are getting very rare.
    Phil
     
  2. KM1H

    KM1H Ham Member QRZ Page

    Many amps can be regettered with no drive (using RF drive is a bad suggestion also when working with an unknown.)

    If the amp uses a bias circuit, such as the SB-220 family, then just bypass it with a jumper wire. As long as there is enough air and the tube doesnt get beyond a bright red you are still OK IF the power transformer is up to it. I use an old stripped down SB-220 CB hacked carcass to regetter the 3-400/500's and 4-250A/400A but Ive done it with a regular amp for decades earlier. If I have to do it for a long time I blow a lot of air on the transformer. ALSO make sure the filter caps arent leaky and adding more current drain on the transformer...the amps meters do not show this.

    My own LK-500ZC amp with the original 1986 Eimacs gets regettered simply by using hard on CW, SSB, every few months or just at 1200W PEP on AM. Red anodes on just peaks is fine if you do it long enough as in a contest.

    The worst thing you can do with these tubes is baby them well below the amps rated power, half voltage on the old CW position is a real no no, they will always outgas and when it is bad enough flash over.

    Carl
     
    N8VIL likes this.
  3. K6BSU

    K6BSU Ham Member QRZ Page

    Here's what I've learned about "gettering". 50% say "nonsense". 50% say "works great".

    My plan. If my tube causes breakers to pop, I buy a new tube. Simple.
     
    W5UAA, AI3V and N2EY like this.
  4. KM1H

    KM1H Ham Member QRZ Page

    Some buy a new roll of TP after a wipe also:eek::rolleyes:
     

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