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power tranny buzzing? help?

Discussion in 'Amps and Cabs [BG]' started by nil, Jul 8, 2001.


  1. The power tranny on one of my (tube) heads started buzzing the other day.

    It's still running fine, no other issues at all - ran it all weekend and didn't skip a beat.

    I know the tranny's on it's way out - but can someone explain what the buzzing would be and whether I could cause further damage by using it?
     
  2. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    How do you know the transformer's on the way out? It's not uncommon for a power transformer winding to get a little loose after some time and cause a buzz. When transformers are manufactured, their layers of windings are often wrapped with tape to keep them from vibrating; maybe yours now needs a little tighter wrapping.

    Another thing to check: make sure its mountings are tight and secure.
     
  3. I've probably always associated tranny buzz with the imminent demise of the appliance! ;)

    But, what you said makes sense - and there's no extra heat or anything silly coming from it...

    I'll have a dig inside...thanks!
     
  4. Yeah, it's the power tranny alright. Even with standby off it's buzzing. I'm convincing myself that it's getting louder, but it's probably just more noticable when you stop playing.

    I'm (slightly) worried that by running it with a dodgy tranny (if it is dodgy) I could bunt something else in the amp (apart from the tranny and fuses).
     
  5. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    I still think it's not much to worry about. From what I've seen here at QSC and previously at Crest, power trannies rarely fail, and those that do seldom fail slowly. (Unless they're real pieces of crap to begin with.)

    Most often, they're done in by violent physical damage, such as the amp tumbling down a few flights of stairs, or by burning out due to overheating plus overcurrent. Burning out may be accompanied by spectacular flames, but more often by acrid burning smells and smoke.

    If the transformer doesn't smell cooked, it's probably still in good shape and might benefit from a little wrap fix as I described earlier.

    -Bob
     
  6. Cool, thanks for that Bob. I'll look at wrapping the beast next time I have it apart.
     
  7. ubersam

    ubersam

    Oct 12, 2000
    L.A.
    I've got a similar prob, but with a non-powered mixer. I was thinking about re-dipping the transformer in that laquer-like solution they dip it in, but I don't know what it's called. (Anybody know?) Maybe I'll try that wrap thing. BTW, any special kind of tape? Or would gaffer tape work?
     
  8. I'm with the others. I think your tx is probably quite OK.

    I've been in electronics for 30 years and have heard loads of buzzing transformers (esp. when under load). I doubt that I've replaced 1.

    Ubersam, the stuff you're talking about is simply known as 'transformer varnish'. The stuff I'm used to using is a kind of orange colour and it smells lovely!! Well, I think it does. When transformers are made they dip them in this stuff then let them dry. You might be able to get some from electronic an hobbyist store. You might be able to drip some into the transformer with (say) a pippette or similar.

    Gaffa tape will not be suitable as it's self adhesive. The adhesive will almost certainly melt, or at least badly soften, so that the tape will come off the tx again. In any case, you probably need to get some varnish between the windings for the cure to ba effective so that taping wouldn't work anyway. Sometimes transformers are overwrapped with a special tape that soaks up the varnush, too, but that's probably not appropriate here.

    Rockin John
     
  9. The way I've heard it done involves using a vacuum pump to remove all the air in the transformer windings, so that the varnish sucks into all the open spaces.

    Pretty cool.

    Chris
     
  10. ubersam

    ubersam

    Oct 12, 2000
    L.A.
    Rockin John, thanks for the lead on the varnish.