Pots on a JCM 800

sei046

Lads pickup up a Jcm 800 50 watt combo and the pots are in a bad way. Whats the best way to sort them out or should i just replace them?

Voodu Child

Well, contact cleaner will help lubricate them and fix minor scratching problems, but if they're completely full of gunk, time for new ones tbh.

sei046

What would be my best bet for new ones? are they hard to swap over?

Voodu Child

sei046 wrote: »

What would be my best bet for new ones? are they hard to swap over?

The exact replacments will vary from amp to amp. I don't know the ins-and outs of the JCM800 but i'd presume it's chassis mounted pots instead of PCB mounted ones. If that's the case, replacing should be a breeze.

The exact type and value of the pots can be had by checking what you've got or posting on a Marshall centred-forum. Im sure google will throw up the info too. bear in mind that lots of JCM800 owners mod their amps by using different (than stock) K pots in the various positions, might be something to consider, and about the simplest 'mod' there is.

Eoin Madsen

sei046 wrote: »

What would be my best bet for new ones? are they hard to swap over?

Not especially, assuming they're chassis mount. Soldering the bus wire is the hardest part. You need a hot iron, maybe 50 watts. Alphas are the favoured replacement, unless you're going for something boutique or military spec. Don't bother with Marshall stock replacements anyway.

There are several different models of JCM800 in both 50 and 100 watt so the exact circuit will vary. But if I recall correctly, the normal pot arrangment is 1M, 1M, 1M, 250k, 25k, 5k. The 1 meg pots are logarithmically tapered, the rest are linear.

The 250k and 25k are 220k and 22k on a lot of models but those are harder values to find these days, and the difference is negligible. And the 5k presence is a 22k/25k on some models too.

sei046

cheers eoin will look into it