Peavey Windsor Loud Hum

Discussion in 'The Workbench' started by JM5010, Mar 24, 2020.

  1. JM5010

    JM5010 Member

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    Hi guys, i have a peavey windsor that hums loudly when the standby switch is turned on...

    This happened after i tried to wire in a JCM 800 style “low input” to use woth pedals. Was working fine before this.

    I’ve troubleshooted by removed preamp tubes, checked my wiring, checked my speaker, and even tapped the filter caps with a popsicle stick to see if that’s the issue.

    Dunno what to do, any suggestions?

    BTW, the amp is wired like the Green Day “Dookie Mod” (modded 2203ish schematic). Sounded great when it was working...
     
  2. JM5010

    JM5010 Member

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    Update: The hum seems to be originating from the PI tube area. Also, there is sound coming from the amp if i plug in my guitar.

    Here are my schematics if it helps.
     

    Attached Files:

    Last edited: Mar 24, 2020
  3. marco_giampa23

    marco_giampa23 Active Member

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    probably a loose ground, depends on the type of hum though
     
  4. ampmadscientist

    ampmadscientist Well-Known Member

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    Put the tubes back in.
    Plug guitar into the effects return.
    Turn the amp on, is there sound now?

    From what you are telling me so far, it's an input jack wiring error.
    Put the jacks back to stock and re-test the amp.
     
  5. JM5010

    JM5010 Member

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    My amp doesn’t have an FX loop, i actually took it out of the circuit.
    Will rewire the jacks to how i had it before.
     
  6. ampmadscientist

    ampmadscientist Well-Known Member

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    Did it work before you wired in the extra jack?
     
  7. JM5010

    JM5010 Member

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    It did. However, the input jacks don’t seem to be the problem. I just wired it back to stock and the hum is still there.

    What usually causes this type of hum? What other places should i check for issues?
     
  8. JM5010

    JM5010 Member

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    May have found the culprit: R22.
    It’s that big white resistor which is part of the bias circuit...gets hot to the touch and seems “crumbled” in the pic. Could this be it? I don’t think i moved the bias pot at ALL, the tubes aren’t red plating or anything.

    If not, where else can i look for any issues? @ampmadscientist
     

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  9. ampmadscientist

    ampmadscientist Well-Known Member

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    Take out the preamp tubes.
    Leave the PI tube installed.
    Leave the power tubes installed.
    Turn up master volume to 10.
    Turn channel volume to 0.
    Does it still have the hum?
     
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  10. JM5010

    JM5010 Member

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    Yep, still has the hum.
     
  11. JM5010

    JM5010 Member

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    Also, there’s a more prominent “buzz” when the master is at 12 o’ clock. Then it goes back to the hum from before once the master is maxed.
     
  12. South Park

    South Park Well-Known Member

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    Some thing is not grounded right in the input . Try to relocate the ground
     
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  13. JM5010

    JM5010 Member

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    I’ve tried that^ already with no luck...should i look in the mixer areas? (470k res/470p cap area)
     
  14. ampmadscientist

    ampmadscientist Well-Known Member

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    What happens when you take out the PI?
    Just the power tubes in does it still hum?
     
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  15. JM5010

    JM5010 Member

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    It only hums with the PI tube in.
     
  16. JM5010

    JM5010 Member

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    Jesus christ...was messing with the master volume pot and pulled it and the hum stopped...

    So i put on the washer and bam! LOL! hum gone!
     
  17. ampmadscientist

    ampmadscientist Well-Known Member

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    I don't exactly understand how your master is hooked up but I'm happy you fixed it...:fever:
     
  18. mickeydg5

    mickeydg5 Well-Known Member

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    So as long as you run the washer the hum cannot be heard, correct?
     
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  19. South Park

    South Park Well-Known Member

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    The pot was not grounding out right
     
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  20. JM5010

    JM5010 Member

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    Correct. It’s so weird...it is what it is.
     

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