Hey guys not a valve amp, but I'm having an issue with my 1986 marshall 5212 2x12 fifty spilt reverb combo.
Basically the gain pot does nothing until it gets to 3/4 of the way up then bam it all comes on at once.
Basically the pot only works in the last 1/4 of its range and it's super sensitive. Like the slightest tweak delivers a massive increase of gain...
My thoughts is that the pots screwed. Any other ideas? Replace or clean with contact cleaner?
Thanks guys
Crazy gain pot???
Moderators: pompeiisneaks, Colossal
Re: Crazy gain pot???
Either a bad pot or possibly it lost ground reference in one end.
I Think I Think Too Much !
- Leo_Gnardo
- Posts: 2583
- Joined: Thu Sep 27, 2012 1:33 pm
- Location: Dogpatch-on-Hudson
Re: Crazy gain pot???
Worth a shot of cleaner spritz, maybe some crud has grown in there that doesn't let the wiper hit the track until it's nearly full up. OR the wafer is split, your track discontinuous, you'll need a new pot.
down technical blind alleys . . .
Re: Crazy gain pot???
It's not a conventional gain/volume pot with one end grounded but a feedback+attenuation pot, with the center lug/wiper grounded.
Replace it with a fresh 22k (or 25k , it's the same) linear pot.
It might have a cracked wafer as suggested above or somebody might have replaced it with a larger value one, say 220k or anything above 50k.
That would also deliver all the gain in the last 10% of rotation.
Replace it with a fresh 22k (or 25k , it's the same) linear pot.
It might have a cracked wafer as suggested above or somebody might have replaced it with a larger value one, say 220k or anything above 50k.
That would also deliver all the gain in the last 10% of rotation.
-
- Posts: 16
- Joined: Sat Dec 06, 2014 10:11 pm
Re: Crazy gain pot???
Thanks guys I have cleaned the pots with contact cleaner and put my multimeter across it and it seems to be reading a normal range, as in as you would expect a good pot to behave.... As the tree said to the lumber jack I'm stumped...