Randall RX120R Solid State Treble Fault

[UltraNamron]

I have a Randall RX120R that one day developed a fault with the treble control on the dirty channel. When the pot is turned up, all the bass is cut from the amp resulting in a very tinny, thin sound. At its lowest position it's very boomy with no treble, it seems to have turned itself into a high pass filter overnight. I repair musical instruments but not amplifiers, I opened it up to have a look if anything was obviously fried, the only thing I could see out of place was some of the glue around the bass of a capacitor was browner than the rest. It sounds like a capacitor fault but I really have no clue, can anyone shed any light on the situation?

Thank you!

[J M Fahey]

The track must be cut, so it's not "a pot" any more but a switch: above the cut/crack you have all treble through a tiny capacitor, Bass can not reach you through open air; at low settings you connect to the mid and high killing Bass capacitor (so sound is bassy muddy) but treble can't reach the wiper.
Replace the pot and it should work properly.

[Jazz P Bass]

Here is a snag of the schematic showing the tone control circuit.

Agree.

Either the pot is bad, the soldering is bad or the 102 (0.001uf) cap is open.

[UltraNamron]

Thank you all, I'll pick up a B50k pot and a new cap just to be sure. Time to measure some splined shafts!

[chiko]

Boa tarde
sou novo no grupo
Tenho um amo Randall KH 120 que ao ligar emite um zumbido tummmmmmmm e depois de 5 segundos para e o amo funciona normal
Alguém poderia me ajudar?

Good afternoon
I'm new to the group
I have a Randall KH 120 master that when turned on emits a buzzing hummmmmmmmm and after 5 seconds it stops and the master works normally
can anybody help me?

[nosaj]

it is best to start a new thread. Do you have a voltmeter? to test for DC on the speaker?
nosaj