3 channel dual rec tone control related failure

[woodbutcher65]

So I was playing my 3 channel dual rec this evening, went to take a break, came back, and found that during my brief absence something had failed.

In the orange channel, the treble control has stopped working correctly and is now working incorrectly.

As the treble control is turned up, the output level decreases dramatically and the tone becomes extremely fizzy and tinny.

It's only the treble control and only in the orange channel. No other channel or control is affected.

It appears that a coupling cap in the tone circuit of the orange channel is at fault.

I'll be investigating and looking at the caps in that part of the circuit, expecting to find one that has failed and shorted.

It should be an orange drop type.

 

[woodbutcher65]

On second thought, it's probably a leaky treble cap. 800 pF. I don't have that value on hand so I ordered up a few.

 

[woodbutcher65]

Sure enough, it was the 500 pF ceramic disc treble cap. Just replaced that, and while I was at it, gave it a new set of filter caps, and it's running great again.

 

[deeman]

Thanks for following up on the underlying issue as well as the successful fix. Hopefully others will be helped in the future!