Ampeg SVT-III (non-pro) quit working mid gig

Discussion in 'Amps and Cabs [BG]' started by sanchothesinner, Dec 28, 2016.

  1. sanchothesinner


    Dec 28, 2016
    I turned off my amp in between the 3rd and 4th set at a show (I know....big mistake as letting the tubes warm up is where it's at). Either way, I tried to turn the amp on and it just wouldn't work. The power cable is fine. Is there any way to know if tubes are the issue ? This thing has worked like a tank for me for 10+ years. I just don't want to buy new tubes if that's not the issue. On the fence between buying a new head or fixing this one, but to be honest everything in my price range is underwhelming and I loved my SVT-III (non pro).

    Any troubleshooting tips? not much info about this amp online
  2. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    It could very well be a tube, and it could very well be something else. If you have a working 12ax7, you can try subbing it out for each tube one at a time. But unfortunately, there's no way to diagnose it from afar, especially with the info given.
  3. sanchothesinner


    Dec 28, 2016
    sorry I just didn't know if there was some sort of diagnostic plug type thing
  4. rufus.K


    Oct 18, 2015
    Does the pilot light come on
    Do the speakers hiss
    Does the clip light engage
  5. sanchothesinner


    Dec 28, 2016
    the speakers hissed. I'm not next to the head but I believe the pilot light came on but no audio. I need to doublecheck. Should've had my ducks in a row before making this thread.

    I'm gathering that the cheapest I can do right now is get tubes then try those out. a transformer might be a possibility too. I don't think it has a clip light.
  6. Bim1959


    Apr 15, 2009
    Naples Florida
    Sales and electronic tech/piano tech: England Music Center - Clinton IA - now closed
    What we need to do is isolate the problem to either the preamp or power amp section. You can start by running an instrument cord from the preamp out into a small practice amp and plugging your bass into the SVT 3. If you get sound there, then do the same to the effects send jack. If you get signal from either or both of those then your preamp is good and there's a power amp problem.

    You also need to turn down the master volume on the amp and plug your bass into first the effect return and then the power amp in Jacks, turning up the bass and turning up the master volume on the amp. You should get a good clean signal. If you get a distorted signal then your problem is the power amp section and the amp needs to go to a shop.

    Good luck!!!
  7. Bim1959


    Apr 15, 2009
    Naples Florida
    Sales and electronic tech/piano tech: England Music Center - Clinton IA - now closed
    If your problem is the transformer you'd smell smoke and see a lot of it. I know because the transformer in my 3 pro burned up a few months ago and I was quoted $350 plus labor to replace it.

    Don't always assume the transformer is the problem because it rarely is. With most amps, IF a transformer goes, it's usually because other components died and caused the transformer to burn up.
  8. farace

    farace Supporting Member

    Jul 9, 2016
    Connecticut USA
    In the "for what it's worth, and it's easy and free to check" category, the only problem I ever had with mine (well, other than the one that caused Ampeg to issue a service bulletin, but that's a different (and long) story) was with dirty effect send/receive jacks, which will frustratingly cut off all sound. Easy to check, just patch a cable between them. I understand this is not an uncommon occurrence.