Peavey 6505 blows mains fuse with amp on standby

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Rocknrollampsinc, Dec 20, 2009.

  1. Rocknrollampsinc

    Rocknrollampsinc Member

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    Hi
    I have a Peavey 6505 on the bench which keeps blowing the mains fuse with the amp on standby.
    1- I removed the power tubes and tried again, same thing. I disconnected the OT, turned the amp on in standby mode, it stayed on. C34 had about 470vdc to grnd. C38 had about half of that which should be correct.
    2- I checked the OT windings for resistance/shorts, short to ground and they seem OK.
    3- Next, just for the hell of it I rigged up a spare 100w OT after disconnecting the stock one. Turned the amp on in standby mode and again it blew the mains fuse.
    So, I have ruled out the tubes, the OT
    4- checked C34, C35, C38, C39 with an EDS-88 CapAnalyzer and they test ok.
    The only schematic I have or that I can find on the internet is the VH 5150ll which people say is the same. I am not sure they are correct.
    Anyone have any ideas. Thank you in advance.
    Jack
     
  2. rockon1

    rockon1 Member

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    No tech...just guesiing-rectifier diodes? Bob
     
  3. Chris Scott

    Chris Scott Silver Supporting Member

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    Disconnect all leads from th PT one at a time, (save for the primaries) and you'll find the offender. If it still blows the main after fils, rectifier and B+ are disconnected, you've got a duff PT.

    I'm no expert, yet I just went through this with an amp. Pretty simple really, just a process of elimination.
     
  4. JerryP

    JerryP Member

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    Shorted flyback diodes on the power tube circuit board.
    Jerry
     
  5. rockon1

    rockon1 Member

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    Ahhh. My money is on this answer. Bob
     
  6. Rocknrollampsinc

    Rocknrollampsinc Member

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    Thanks to Jerry, :bowamp is repaired and back in service.
    JK
     

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