Repair Ampeg Amp in Northern California. Worth it?

Discussion in 'Amps and Cabs [BG]' started by xavierandrade, Jul 15, 2020.

  1. xavierandrade

    xavierandrade Supporting Member

    Jul 5, 2012
    Hi! This is my first time posting in this forum but I have been reading it for a while.

    I just got my hands on an Ampeg SVT 6 pro that needs repairs. There was a short that burned part of the circuit board on the amplifier part (see picture). However the preamp part works (the DI gives sound, even though with a lot of background noise).

    I would like to get it repaired in some place with experience. Does anyone know such a place around the Bay Area? How much should I expect to pay for such work?

    Is it worth repairing it or will I end up paying more that what it is worth? I know a bit of electronic so I could try to do it myself, but the chances of me screwing up something are high.

  2. How long is piece of string? Unless someone can point to that and say ''I have fixed that fault a couple of times, the XYZ blows and takes out the doofer and the whatzit, half an hour tops'', it's guesswork and even then there could be more to it.

    At least it looks oldschool repairable if you know what you're doing.
  3. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    There are quite a few parts that are damaged aside from the 4 or 5 that are visible. The bigger challenge is that there may be hidden damage to the underside of the PCB where excessive currents may have damaged traces. Also, the damage to the PCB laminate may be more seriously burned than it looks, the resins carbonize under heat and they are somewhat conductive, so the cleaning needs to be thorough and aggressive.

    Sure it's repairable, the entire PCB may be available as a replacement part (might be less expensive because there could be a lot of additional parts plus a lot of expensive labor), but you will need to decide how much it's worth investing.

    Based on my GENERAL experience, (hypothetically) if I were to repair it, I would expect about $125 in parts (mostly power semiconductors) and at least 3 hours of labor @$85/hr) or around $400+. This is not an easy repair.

    How much do they sell for used? You may be better off going that route but be darn sure it works and is in decent condition.
    BassmanPaul and Wasnex like this.
  4. xavierandrade

    xavierandrade Supporting Member

    Jul 5, 2012
    Thanks for the responses! I know it is hard to give an exact estimate, but I wanted to get in the ballpark of what a repair might cost to decide what to do. It is probably not worth to do it since a working one costs around $400-500 according to reverb.

    So I am going to try to fix it myself, since at the end I got it for free. The thrift shop were I bought it gave me a full refund and let me keep it. Worst case I still learn, and I just use it as a tube preamp.
  5. dlb1001


    Jan 30, 2007
    Contact Keith Holland at Keith Holland Guitars in Los Gatos. He has a person (Randall) who comes by Keith's shop and pick it up the amp. Randall has his own shop, which he would diagnose the problem and give you an estimate.
    Agedhorse's estimate is probably in the ballpark for fixing it.
    Kevnn4 likes this.
  6. BassmanPaul

    BassmanPaul Inactive

    Before you get started, how many amplifiers have you successfully diagnosed and repaired? Do you have the requisite tools needed to effect such a repair? Using the amp in any capacity unprepared could be dangerous and pose a fire risk.
  7. BogeyBass

    BogeyBass Inactive

    Sep 14, 2010
    Toasted traces have been repaired before.

    Never a easy process.

    Parts get removed from the area and you clean the carbon off to get a better look.

    Then you look for few things.

    1, What traces have been burned
    and how , or if possible to make bridges that will stay in place

    2 visual check to surrounding traces, also meter check surrounding traces.
    Because as mentioned, sometimes it burns the actual pcb material to much. and you have carbon tracking to other traces. No amount of surface cleaning can remove carbon tracking if the substrate is to burned.

    It's been done before, but is either done because a replacement board is impossible to find, and or the owner is very in love with the amp

    Full compass, use to stock alot of Ampeg boards. Far as what's still available. I'm not sure.
    Sometimes things look really black and ugly and not to bad. Sometimes things look not to bad but 5 others traces are carbon tracked in the board.

    Can't give a exact circuit analysis. But a resistor got hot obviously and blew. But there is likely another bad component that caused the high heat.

    Looks like dropping resistors to the opamp as quick guess. Possible dead opamp or low voltage circuits. Assume the usual dead zeners or toasted opamps. Ampeg likes to push power amp drivers at 22 volts instead of a modest 18. Works fine till the opamp pulls to much current.

    Alot of board jumpers, your somewhat lucky, probably single sided board. Double sided boards are nightmares for burn through
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Going to be more parts than this, guaranteed. There's at least 1 destroyed cap a couple of resistors, etc.
  9. rufus.K


    Oct 18, 2015
    Thats gonna take a whole lot of duct tape and crazy glue.
  10. Old Fart

    Old Fart

    Mar 11, 2011
    JB Weld.

    Kidding. Not kidding: Not worth it, IMHO.
  11. rufus.K


    Oct 18, 2015
    Jb weld, is it conductive?
  12. I had a blues junior I bought at the pawn shop for $200 a few years ago. My kid used it quite a bit for about a year but it wound up failing because of two big ceramic resistors on the PCB that burnt up and took the PCB with it.

    They replaced the whole assembly as a populated board and the total cost was $225 CDN. The part was $125.
  13. BassmanPaul

    BassmanPaul Inactive

    IMHO the safest way to repair that amplifier is with a board swap if available. Patching the existing board will be a chore to say the least.
  14. I have found disposability to be a sad fact of life when it comes to typical consumer-grade amps.
  15. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    This isn't disposable because of disposability, but because the damage is really quite serious.

    This kind of damage is not unique to solid state amps, I have also seen it with tube amps.

    Whenever there is a catastrophic failure, there is a chance that this kind of damage can occur.

    Before assuming that such expensive repairs are exclusive to solid state type amps, lets consider that an output stage failure can result in similar internal damage to output transformers. The costs are quite similar and replacement of the part in both cases is the solution.

    Both situations are essentially the same degree of disposable, except that for a quality tube amp, the cost of replacement is usually high enough to justify repair.

    It also depends on how well supported the amp is, and if replacement assemblies are available.
    BassmanPaul likes this.
  16. abarson


    Nov 6, 2003
    Santa Cruz
    One of my previous bands was given a Sunn powered mixer that "needed some repair". I opened it up and found a hole burned through a power supply PCB. I did my best to try and find schematics, finally gave up and sold it for scrap. Got $50 for it, and figured it was the best outcome all around.
    agedhorse likes this.

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