Roland JC-120

[mitch]

Hello - My friend has a JC-120 that he claims the bright switches on either channel do not work, which sounds kind of odd to me. I'm not all that familiar with S.S. stuff but looking at the schematic it appears to me that the bright switches are just adding C-5 & C-6 to the circuit kind of like a cathode R by-pass. Is there something else I should be looking at that I'm not getting? Seems unlikely that both caps or switches would fail at the same time. Here's a link to the schematic. http://www.freeinfosociety.com/elect...C120-JC160.pdf
I appreciate any input anyone could give me on this cause I'm no tech by a long shot. I've just built a couple of amps and now everyone wants me to fix theirs when something goes wrong. I don't mind helping them out but I don't want to make things worse either. Thanks in advance - Mitch

[Jazz P Bass]

It does seem odd that both switches do not react.
That circuit is a treble peaking circuit.
Either the swiches do not switch, the capacitor is not or the resistor is not.
Prove it out.
The switch & the resistor are easy to check with a meter.
The capacitor either passes high frequency or it doesn't.

[mitch]

Thanks for reply Jazz -Ah! a treble peak circuit. It seems simple enough, may only concern was both going at the same time and maybe something else I'm ignorant of was the causing issue. Well I guess I delve into it and find out....Thanks again!