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Any way to test a 6L6...

Discussion in 'Glowing Bottle Tube Amp Forum' started by charlie chitlin, Sep 25, 2017.

  1. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

    Age:
    56
    Mar 17, 2003
    Spring City, Pa
    ...with a regular VOM?
    I just want to know if it's trashed.
    Pretty sure a bad 6L6 shut my amp down.
    The tech said it was bad, but he taped the pair together and said both were bad.
    They were an old set and he figured if one was shot, the other can't be far behind.
    I'm a little more optimistic and would run the OK one in something.
     

  2. archetype

    archetype More tone than talent Ad Free + Supporter

    738
    Jun 4, 2005
    Williamsville NY
    All you can tell with a VOM is whether the heater has continuity and whether things are shorted that shouldn't be. I'd say it's a waste of time. You need a friend with a real tube tester. It the tubes aren't "bad," then stick them in the amp and listen to them.
     
    SnidelyWhiplash likes this.

  3. dr_tom

    dr_tom Tele-Meister

    319
    Sep 21, 2013
    Ontario
    I remember the days when my father would send me to the local convenience store with old tubes to test them out on the tube tester! That was always a fun job.
     

  4. thegeezer

    thegeezer Tele-Holic Gold Supporter

    Age:
    65
    661
    Jul 5, 2010
    West Michigan
    Know anybody with a single ended amp, like a Champ?
     
    telemnemonics likes this.

  5. Old Tele man

    Old Tele man Tele-Afflicted

    May 10, 2017
    Tucson, AZ
    Tubes are "high-voltage" devices, and must be tested using high voltages (typically ~250VDC). They cannot be testing using simple VOM like some transistors.
     

  6. Strato50

    Strato50 Tele-Meister

    Age:
    50
    439
    Mar 30, 2017
    Port Arthur TX
    I am lucky to have my old NRI tube tester...saved me a bunch of time and money.
     

  7. Old Tele man

    Old Tele man Tele-Afflicted

    May 10, 2017
    Tucson, AZ
    The RIGHT tool for the right JOB!
     
    brokenbones and JustABluesGuy like this.

  8. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

    Age:
    56
    Mar 17, 2003
    Spring City, Pa
    I was just wondering if there's a way to tell if a tube is shorted or something.
    I don't have a single ended amp that uses a 6L6, and I'm not sure I'd want to use a nice amp as a tube tester.
    I've seen some serious damage happen without the fuse ever blowing
     

  9. Strato50

    Strato50 Tele-Meister

    Age:
    50
    439
    Mar 30, 2017
    Port Arthur TX
    You need a tube tester.
     
    Hiker likes this.

  10. dsutton24

    dsutton24 Poster Extraordinaire Gold Supporter

    Dec 29, 2010
    Illinois
    No.

    A VOM has a battery in it, something between three and nine volts, depending. Many times a device will appear to test 'good' with a VOM, then do hideous things when high voltage is applied to it. Add to this that what happens in the internals of a tube changes a lot when it warms up and you can see the difficulty.

    You need to find somebody with a tube tester. Tube testers themselves are no guarantee, but you can at least check emission and check for shorts. Why not just ask the guy who worked on the amp to test them for you?
     

  11. Strato50

    Strato50 Tele-Meister

    Age:
    50
    439
    Mar 30, 2017
    Port Arthur TX
    Send them to me I will test them for you.
     
    Hiker likes this.

  12. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

    Age:
    56
    Mar 17, 2003
    Spring City, Pa

  13. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

    Age:
    56
    Mar 17, 2003
    Spring City, Pa
    Because he's 45 minutes away and I SOMETIMES get one day off a week.
     

  14. dsutton24

    dsutton24 Poster Extraordinaire Gold Supporter

    Dec 29, 2010
    Illinois
    I was trying to be helpful. Just how would I have known either of those things?
     

  15. Zeonoid

    Zeonoid Tele-Meister

    Age:
    38
    252
    Dec 17, 2008
    Slovakia, EU
    check the cables that goes to the power tube sockets inside ot the amp.. if one is loose at the connection then even good tubes can fail
     

  16. MA6200

    MA6200 Tele-Meister

    139
    May 12, 2017
    Maryland
    His tech needs a tube tester too!!
     
    SnidelyWhiplash likes this.

  17. radiocaster

    radiocaster Friend of Leo's

    Aug 18, 2015
    europe
    The problem is if only one is fried, it would be hard to find another somewhat used 6L6 to match it unless you have a stash of tubes.

    If you have a single-ended amp with just one 6L6 you can put it in there and see if it works. Otherwise you'd be better off giving to someone who does.
     
    Last edited: Nov 26, 2017

  18. mad dog

    mad dog Friend of Leo's

    Jun 27, 2005
    Montclair, NJ
    I would accept his judgement on the trashed tube, and ditch it. If you have other 6L6s around, you can try to match it in the amp by biasing. Happened to me recently with NOS 6v6s. Bought a set of RCA blackplates from a trusted seller. One of the tubes bailed a year later. It happens. As it happens, I had 4 or 5 more or less equivalent blackplate single 6v6s in the box, only one of which was an RCA from an earlier set in which one had died. So I put the known good tube in, tried every other next to it, with the biasrite hooked up. The single RCA was not even close. One of the others was close enough in Ma. No name. And voila. Sounded just as good as the original pair.
     

  19. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

    Age:
    56
    Mar 17, 2003
    Spring City, Pa
    He's very fastidious and has gotten himself in trouble with customers who wanted old glass but didn't understand the foibles.
    There was 1 bad tube amd he taped the pair together and marked them "bad".
    He also suggested I not use any of the old tubes I gave him to try in the amp and get a new set from TAD.
    I understand his point. I would probably do the same if I was expected to stand behind work on 60 year old amps that my customers wanted to put 60 year old parts in.
     

  20. mad dog

    mad dog Friend of Leo's

    Jun 27, 2005
    Montclair, NJ
    Charlie: didn't realize he didn't ID the bad one. That's a different deal. Introduces risk in trying to use the remaining (allegedly) good one.

    I understand his point too, but rely on my own judgment about tubes too, when there seems to be no danger involved. Have had more than one otherwise totally cool tech pull and toss a NOS preamp tubes and replace with "more reliable" modern equivalent. Now I get this stuff clear in advance, so no misunderstandings.
     

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