Need Help - Issues w. Pot Replacement

Discussion in 'Shock Brother's DIY Amps' started by joel_ostrom, Mar 1, 2013.

  1. joel_ostrom

    joel_ostrom Tele-Afflicted

    Posts:
    1,135
    Joined:
    Sep 11, 2006
    Location:
    Calgary, AB
    Hey all - so a bit of background for you: I'm refurbishing an old Fender M-80 1X12 amp. The pots were all extremely scratchy and staticky when you'd turn them, sometimes signal would cut out completely so I opted to replace them instead of cleaning them out (tried deoxy cleaner, didn't work).

    Right now i'm in the middle of replacing the pots. Now these are the kind of pots that were originally installed 37596.jpg

    but i'm installing standard alpha pots. I understand that because the snap in pots have 4 pins to ground I will have to jumper the ground terminals on the PCB with hookup wire (which I have done, no problem).

    My problem comes with the first pot that I installed. It works just fine, no scratchiness or static when turned but - the taper is backwards. When I turn the pot counter-clockwise, the volume goes up. Clockwise, it goes down.

    Do I have the wrong pot for this?

    I purchased the pots from Small Bear Electronics Online
    I acquired the pot specs from the layout and schematic of the amp itself that I got from Fender.

    Here's a shot of the work i have so far:
    IMG_0167.jpg

    You can see how i've soldered all the jumpered ground points to the 1st terminal on the pot and the hot leads to the 2nd and 3rd.

    The Volume Pot (Clean Volume) that i'm having the problem with read 30C50K. As I understand it, this means that it is a 'C' type taper. I have read from an article using this chart:
    Screen Shot 2013-02-28 at 11.35.34 PM.png that 'C' was the old code, and is now referred to as 'A' taper.

    Did I wire this up wrong?
    Or do I just have the wrong tapered pot?

    Any info you guys can give is greatly appreciated.
    Thanks,
    Joel
     
  2. BobbyZ

    BobbyZ Doctor of Teleocity

    Posts:
    11,896
    Joined:
    Jan 12, 2011
    Location:
    Snellman MN
    If it works backasswords you wired it wrong. I would flip the wires on the outside posts and try it,
    If that don't work you'll have to figure it out from the schmatic.(or post one here)

    A word of caution.
    I haven't had my coffee yet this morning.
     
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