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bassman 100t power tubes

Discussion in 'Amps and Cabs [BG]' started by muncie, Jul 22, 2012.

  1. Dear kind TB'ers,
    I recently purchased and received a new Bassman 100t amplifier and I noticed that one of the four power tubes is a bit smaller (shorter) than the other three. I'm not totally inexperienced with tube amps but I've never encountered this anytime before. Is it reasonable to expect vacuum tubes to vary slightly in size? If not, is there any reason why a tube with "less glass" would not perform up to standard? In other words, should I be thinking of replacing it based only on it's appearance?
    Thanks so much for reading this.
  2. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    I would not worry, but exactly how much smaller are we talking?
  3. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    If a tube is truly short when the rest are tall, I'd be getting on the phone with Fender CS because that's unacceptable in a new amp IMHO unless there's a specific reason for it (and I can't think of any). But first, check and make sure that the other tubes didn't just come a little loose in the sockets and are standing taller. I know, probably a silly suggestion, but stranger things have happened.
  4. PlungerModerno


    Apr 12, 2012
    Try and find a diagram. It could be a pre tube. Power tubes are typically bigger and matched in type to keep the power section simple (less chance of failure).

    That's as far as I know. Which isn't far. TB has plenty of tube people with loads to offer on the topic.

    EDIT: +1 to the above!
  5. All the output tubes should look the same on a new amp (or re-tube). One being a different size glass could indicate one was broken and a non-matched tube just stuck in the socket.
    I'm not that big a believer in matching, but in a new amp they should all look the same period (different makers may use different bottle sizes).
  6. thanks all for the responses. here's a visual reference... it looks like the other three could be seated a bit better but I still don't think they'd be even.

    Attached Files:

  7. Wow that's noticeably different...

    I don't have much more to contribute other than to talk to Fender's CS because that's pretty apparent that they're different. I would hope with a brand new amp that there wouldn't be that much difference.
  8. Linnin


    Jul 19, 2012
    Linningrad, Earth
    Looks like one 6L6 is from a different manufacturer. No way can that be a matched quartet. I'd replace them with a matched quartet from your favorite high end tube manufacturer. I like Groove Tubes. You may like somthing else such as NOS RCA's or Sylvanias. My '79 blackface Fender Studio Bass amp came stock with Fender branded Sylvanias, and they rocked out BIG TIME!
  9. Auguste


    Apr 5, 2012
    A recently purchased new amp

    Odds are the store had to change a tube

    Should not have come out of Fender like that

    Call Fender and send a picture

    At very least you should get a new set of matched tubed tubes sent to you over night
  10. Doesn't the 100 have automatic bias? Doesn't that mean you don't need to have a matched set?

    I would still expect a brand new amp to have matching tubes. I agree that something happened to the original tube and it was replaced by one from a different manufacturer.
  11. BogeyBass


    Sep 14, 2010
    Its actually no big deal, sorry to say it is what cheap tubes look like sometimes. My Blues Deluxe reissue came with factory tubes that looked odd in size to.

    The glass is just malformed slightly shorter, as long as the guts work...who cares.

    if it really bothers you spend some money on new tubes.
    then keep the factorys in the new boxes as back up.

    The factory tubes in my Blues reissue sounded like krap, after I replaced them. It sounded pretty darn good. They really didnt last very long. The amp really waked up after changing the preamp tubes. Sorry factory tubes are really crappy. and the difference was more than noticeable. Output tubes not as much, preamp big difference.
  12. Looks to my old eyes to be a bit of poor assembly on the base of that one tube. The glass itself "looks" to be the same but assembled crooked in the tube base. Not a functional problem but a result of the quality control in new production tubes?
  13. hey muncie i didnt notice any name on the tubes but can u tell the manufacturer of the tubes? or does anyone know if fender makes their own? i read somewhere fender uses groove tubes on some of there products. My 100t will be here Tuesday!!! sooo stoked! Sweetwater sells groove tubes and i was thinking of purchasing all new tubes and keepin the factorys as backups. I was just recently approved for 5000 dollar credit limit with sweetwater card. Thats probably bad news! LOL. And yea im with a few others when they said contact Fender CS they should hook u up if its a defect.
  14. Fender's parent corporation owns Groove Tubes. Neither one MAKES their own tubes. Just buy, test and match other's production.
  15. Hi.

    You get what You pay for :).

    Elaborate please.

    The size of the envelope has absolutely no measurable difference in a set of tubes. As far as the "matching" goes anyway.

    Quite like saying that as long as the tubes in a set look the same, the set is matched.


    That's what the mundane tube amp manufacturers/rebranders count on, hence the often "less than perfect" selection of the factory tubes.

  16. I'm lookin on my phone only, but they don't look too different to me. As stated above, just poor QC in tube manufacturers imo.
    If it's all working as it should, I'd leave it as is. As always, not a bad idea to have spare set of power & pre amp tubes on hand, so grab some & use them, or the original set & the others as spares.
  17. thanks everybody for the input.
    the stickers on the bottles are facing forward...
    they are GrooveTubes 6L6GCs.
  18. christw

    christw Get low!

    May 11, 2008
    Dayton OH
    ...and it could well be a factory matched quad based on how they test. Just sayin' ;)

    Unless it's causing a performance issue, I wouldn't worry about it.
  19. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    looks like 1 is seated well and the other 3 not so much...
  20. Oh my god!!!!! Actually hearing the 100t in person and playing thru it is 100 times better then any you tube video!!!!! im in love

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