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3-500 Taylor Graphite tube, need advise...

Discussion in 'Amateur Radio Amplifiers' started by KB4MNG, Mar 11, 2013.

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  1. W1QJ

    W1QJ Ham Member QRZ Page

    Carl has repeatly said that he has degassed (if you will accept that terminology) several 3-500 tubes and others. I have no reason to not believe that is true. Tom W8JI expalins a process in doing so on his website. Both of these guys claim they have "degassed" tubes that had a level of gas that "I assume" can be absorbed by the getter material on a 3-500 or the getter itself in other tubes. If you (Bozo) haven't attempted it yourself I can't imagine you can discount the fact that it can be done. Personally I haven't myself but I certainly would not say it is impossible if I never tried it. BTW...I did take your advice and I did read up on the gettering process, although I have read it before I still came away knowing a bit more than I did the last time. The actual gettering process is not rocket science however the workings on the process to lay the getter material on the anode is some pretty heavy stuff, I agree. But there is no denying the fact that a getter absorbs gas molecules in the tube, that's what it is suppossed to do. The question is, will the getter still work after a tube is inactive, has a certain amount of gas, and the getter asbsorb it when it is activated at the right temperature? My readings DID NOT address that fact. The only absorbtion of gas my reading spoke about was the initial bit of gas residue left after the tube was pumped down. The getter is suppossed to keep the tube free of gas molecules during normal activity during it's life. I saw no metion in my reading addressing the fact of what will be if a tube sits dormant for some time and becomes gassy. It appears that most information written about tubes is written with the assumption that the tube is being used in commercial service on an ongoing basis. I never see any mention of the type of use us hams put tubes through. If you can't give me a better explanation other than it can't be done, I can't accept that over someone who has actually done it successfully.
     
  2. AH6RR

    AH6RR Ham Member QRZ Page

    Please explain why the 2 3-500Z's I have in my sb-220 with date codes of 74 and 76 still put out full power. I know for fact the amp sat unused for over 3 years in a carport covered by a blanket in the rain forest and it took me 4 months to completely strip down and rebuild and paint it and it worked perfect the first time I hit the on switch. Now since Eimac made tubes mostly for the broadcast industry where the tubes would be run full tilt 24/7 their "Care and Feeding of Power Tubes" would apply. But since in the amateur radio service the tubes are pushed no where near the same as in the Broadcast service they would tend to sit for long periods and develop gas via leaks in the seals ect. But since the gettering material does not get used up like in the broadcast service why cant they be degassed by getting the anode red to activate the gettering material since it still has some left? So Richard or may I call you Dick? Please explain it to this High School drop out who joined the US Navy in 1970 and was trained as a UDT/Seal sniper in simple language that I can understand why you cant do it please.
     
  3. W1QJ

    W1QJ Ham Member QRZ Page

    Geez...all we are asking is to give us a simple explanation to prove his point and this is what we get. What a cop out. I suppose he doesn't have any evidence to provide and is just being his own contrary self. Gee, you would think that after all these years the ARRL has been publishing the handbook that some PHD ham would have sent in corrections in the past 50+ years. Maybe your PHD professor was wrong and that is why you are misinformed and no one agrees with you on so many matters discussed here.
     
  4. N2EY

    N2EY Premium Subscriber QRZ Page

    Because you got good ones. Simple as that.

    Actually, amateur service is much tougher than commercial service in many ways.

    First off, commercial equipment designers tend not to push tubes as hard as hams do. CCS and ICAS ratings and all that. (btw - did any commercial broadcast transmitters use 3-500Zs?)

    Second, in commercial service the usual operation is that the transmitter is turned on, tuned up on a particular frequency, and then left running 24/7. In a year, a BC transmitter will put 8766 hours on a tube (365.25 days in a year). But amateurs tend to change frequency, turn the rig on and off frequently, etc. A ham who operates 2 hours a day, every single day, will take 12 years to put 8766 hours on a tube.

    Third, all that turning-on-and-off is a hard life too.

    It is my understanding that the issue with the seals is all about quality control. Some of them leak more than others.

    73 de Jim, N2EY
     
  5. W1QJ

    W1QJ Ham Member QRZ Page

    Thanks for the information but you failed to address the issue at hand. To remind you, the issue is, can a tube that has "some" gas be degassed by activating the getter (as has been suggested by a few) to absorb the gas? Yes, no or maybe?
     
  6. N2EY

    N2EY Premium Subscriber QRZ Page

    The answer is, of course, "maybe". If the getter material is in unused shape and there's only a little gas, maybe it can be done. In other cases, the tube is toast.

    Reactivation/rejuvenation of thoriated-tungsten filaments is similar - sometimes it works, sometimes it doesn't.

    Only way to know is to try.

    73 de Jim, N2EY
     
  7. AF6LJ

    AF6LJ Ham Member QRZ Page

    I am hoping for that I was going to pick up one of the ones from Harbash and do the shield mod, om version of it anyway, but they are all gone now..

    Knowing the bit I know about vacuum systems and how materials behave in a vacuum, the only gasses that would be impractical to be gettered would be the inert gasses. Contrary to popular belief glass is porus.Helium and the lighter gasses will make their way thought glass. Since its difficult to get those gasses to combine with other materials that would make gettering those materials to a heavier state next to impossible.

    As I stated above contamination is unavoidable in the manufactorer of vacuum tubes and other vacuum sealed components, a single fingerprint can offgass for weeks. I'm sure everyone here has seen how che Chinese make 811s, that should make you shudder. I know seeing how dirty the environment is where those tubes are made makes me want to not walk but run away from Chinese made 811s or 572Bs that are not screened and at least burned-in for a time.

    By the way....
    Does anybody know what is used for gettering material in the 3-500s?
    What chemical the material is and is it a form of ceramic, exactly what is it?
     
  8. W1QJ

    W1QJ Ham Member QRZ Page

    I read zarconium or moly bendum (sp) There are other materials used I think also, but the zarconium seems to be what the 3-500 uses. It also appears that during the pump down process the getter was activated by inductive heating.
     
  9. AF6LJ

    AF6LJ Ham Member QRZ Page

    Interesting...
    You would heat the anode during pump down, that will besides consuming the gross gasses it provides a pressure for the system to work against and get the tube down to a lower pressure.
     
  10. AH6RR

    AH6RR Ham Member QRZ Page

    Sue wrote "I am hoping for that I was going to pick up one of the ones from Harbash and do the shield mod, om version of it anyway, but they are all gone now.."
    I was going to do the same thing Sue and the Harbach website said there was 3 left so I placed the order only the have Jeff tell me they were gone man was I bummed. Then I found a guy in Alabama that had a outboard transformer (Peter Dalh) that was 4KV at 2amps for the 220 at $300 but the shipping was $285 so I passed on that one.


    As for 3-500Z's being used in the broadcast industry I am not positive but I think they were used as driver tubes in very large AM transmitters along with 3-400, 4-400 and 5-500's in the 60's and 70's. When I lived in Texas before I moved to Hawaii I had a 3-500 and a 3-1000 pulls from 2 AM station's that a buddy's dad was the engineer for that I had in my collection of tubes.

    So now that I am on ignore geez I feel I am in High School again:rolleyes:. I did get my GED and went to an electrician apprentice program after the Navy and built Oil Refineries working on the HV crew. 14KV at thousands of amps is fun but you only make 1 mistake.
     
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