Peavey XR600B Repair

Discussion in 'Amp Tech Center' started by dkal24, Sep 24, 2020.

  1. dkal24

    dkal24 TDPRI Member

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    Hello all.

    I have a Peavey amp that I can use if I can fix it. It had a blown fuse in it so I replaced it and powered it up. The hum was very loud without any speakers hooked up. I only kept the power on for a couple secs. The new fuse did not blow. I opened up the amp and everything looks fine inside.

    The amp is a 1982 model, schematic 400BH. Some output transistors are known to fail on these older amps, but I sure can use some input from you guys. Let me know what you think.
     
  2. rangercaster

    rangercaster Poster Extraordinaire

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    It's not even 40 years old yet, so just a minor issue....
     
  3. Jon Snell

    Jon Snell Tele-Holic

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    Check the output transistors first. There will be a few damaged but replace all of them to be on the safe side.
    Check the driver transistors.
     
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  4. dkal24

    dkal24 TDPRI Member

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    YEA.... the weird thing is this amp crapped out 30 years ago. I just shoved it under a chair and bought another one. Also this amp was worked on after it left the Peavey factory. It has 3 different brands of output transistors installed....from what I read, all 8 should be the same brand.
     
  5. dkal24

    dkal24 TDPRI Member

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    I'm about to pull all the output transistors but I'm not sure which one's are the drivers.
     
  6. Bill Moore

    Bill Moore Tele-Afflicted Silver Supporter

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  7. Jon Snell

    Jon Snell Tele-Holic

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    Screenshot 2020-09-25 at 08.14.01.png
    The drivers have their emitters, connected to the base of the output transistors and 'drive' current into the bases which, in turn, drive current into your speaker load.
    Q2 drives Q3 that drives the output transistors.
    Check any resistor with the triangle next to it, R25 & R26 etc and if failed replace ONLY with the same fire proof type!
     
  8. dkal24

    dkal24 TDPRI Member

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    Thx Jon
     
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