MKIII issues

[johndandry]

I bought a used MKIII Red Stripe. It's got some issues.
when you turn the volume control closest to the input jack up past 4, the volume cuts out.
Same with the bass control, above 4 or so, volume disappears. I figured it was bad pots...changed the 1meg to a brand new CTS.. did the same thing.
What should I look for? thanks

 

[McBarry]

Tough call, but shotgun replacing is prolly not gonna do it - as you've found out..

I'd be chasing voltages and chasing a sig-gen signal to see where it stops - all of which is bench kinda stuff with at the very least a constant signal source and a DMM..

There's a multitude of possibilities - we'd only be guessing at this stage.. and usual caveats apply - big volts inside, so big care, discharge caps, be big safety-aware..

Good luck with it... Dave

 

[johndandry]

Fixed it. I changed both caps in the tonestack and eveything is normal in Mkiii land for now.
in the process I burned the trace at the .1uf but I got it to stick, I may just have to solder the wire to the end of the cap later and bypass that trace all together... but for now I got a mismatch of a original .047 mustard cap and the only .1 I had around, a old blue Paktron from a fender
I bought this amp from a guy for $300 because of this problem and turned out to be a $4 fix.