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Ampeg SVT-7 PRO Search

Discussion in 'Amps and Cabs [BG]' started by Jim Pierce, May 21, 2020.


  1. Jim Pierce

    Jim Pierce

    May 21, 2020
    My son has a Ampeg SVT-7 Pro that had an issue cutting out. After a little research we found an issue with U2. The problem is we found it a little late as U2 decided to let go and smoke a bit. I would like to repair this for him as its gotten a bit quite. I've tried searching for a schematic but with no success. What I need to know is the part numbers for the Diode D9 and the Capacitor C36. I already have the replacement for U2 with a heat-sink. Any assistance would be appreciated.

    Jim
    Wizardpcb
     
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    How much electronics experience do you have? Do you have a scope? Do you have experience working with high voltage PWM circuitry?
     
  3. Jim Pierce

    Jim Pierce

    May 21, 2020
    I've been a PCB designer for 30 years and have spent the last 7 as a manufacturing engineer in OR. I have a lot of people that I work with that can assist with the R&R of the components and a test department that can verify. Would love to get my hands on a schematic.
     
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Then start measuring around the PWM controller and see where what you measure doesn't agree with what you would expect for the typical drive circuitry. That would include the drive line snubbers, the output MOSFETs, any push-pull drivers, of course the PWM controller IC. You might be able to lift the drive lines from the controller, or remove the output MOSFETs to verify proper operation of the PWM gate drive signals.

    Or, you can replace the entire PCB for (generally) less than the labor required to effectively troubleshoot and repair the existing assembly.
     
    BasturdBlaster, Geri O and KaseOfBass like this.
  5. Jim Pierce

    Jim Pierce

    May 21, 2020
    Great reply lots to look at, would be a tad easier with a schematic though. Not replacing the board, this is a good unit when it’s working.
     
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    The replacement assembly is not very expensive compared with the challenges of repairing. I strongly urge you to consider it.
     
    BassmanPaul and BasturdBlaster like this.
  7. Jim Pierce

    Jim Pierce

    May 21, 2020
    Considered component total under $10 remove and replace components and testing Zero. I got to try.
     
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    If your time has no value, or you are just looking for a challenge, have at it.

    I've been known to repair or restore something just for the challenge.
     
  9. Jim Pierce

    Jim Pierce

    May 21, 2020
    Sorry but no
     
  10. mickbellinello

    mickbellinello

    Apr 19, 2020
    Italy
    I tried:(
     
  11. ugly_bassplayer

    ugly_bassplayer Supporting Member

    Jan 21, 2009
    Québec
    7 pro cutting out and blowing up.

    No!!!! Impossible.
     
  12. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Worked fine for me, FWIW. Yel_wink.gif

    But relying on a specific revision schematic from a non-authrized source is not always the greatest plan IMHO.
     
    BassmanPaul and mickbellinello like this.
  13. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Agreed, especially when the revisions address the specific issue the OP is dealing with.
     
    mickbellinello and Passinwind like this.
  14. Jim Pierce

    Jim Pierce

    May 21, 2020
    Got the schematic and sorry to say but it checks out with the board Revision we have. I also have additional upgrade information as LOUD went from REV A to REV H. So I'll let you know what happens in a few weeks, components are on order and test engineers have scoped what we can for now. Thanks for your help.
     
    Jim C, Lovep, wave rider and 2 others like this.
  15. mickbellinello

    mickbellinello

    Apr 19, 2020
    Italy
    I apologize but I thought it could be useful... I took the infos of those sheets was good, I'll take more care in the future. ;)
     
  16. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    That's a very hard document to come by. My buddy owns an authorized Ampeg repair facility and he says they can pull his license if he lets a schematic go out the door.
    Good luck on the repair!
     
  17. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    I think you can understand Ampeg's position given the amount of knock off, copied product coming out of the far east.
     
    BassmanPaul and wcriley like this.
  18. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Yamaha’s Ampeg policy has been to release schematics to the public for retired products but not current ones. I can’t blame them. In the past, you could buy service documents from Yamaha. The large foldout schematics were great. Some would wind up on a wall so I could refer to them. To me they were like a work of art.

    Loud would provide a schematic if you requested it and supplied a serial number. As a result, many of their schematics can be found on the internet. At one time they made a CD available with all their products and service tech notes. That’s how they were distributed to service centers. Then they had a service web site with documents available. Much easier to obtain the latest revisions digitally.
     
    Jim C likes this.
  19. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Yes, it makes complete sense.
    Quite honestly, with the complexity of these new amps, I would think there are few individuals that really have the experience and knowledge to trouble shoot let alone deal with SMT components.
    @Jim Pierce on the other hand sounds like the exception and I wish him well!
     

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