Beta Lead Ticking

[porcupine]

I picked up my first Beta Lead for pretty cheap off Craigslist ($180!) and have spent the past couple days cleaning it and learning its ins and outs. I cleaned all of the jacks and pots and took a look at the PCBs to see if there were any obviously damaged components. No obvious damage, though it looks like someone added an electrolytic capacitor to the solder side of the preamp board.

Everything seems to be working, except the amp produces a ticking sound when Drive A is set below noon. The ticking is slow when the drive is turned counterclockwise and starts going faster as the pot is turned up. The pot works -- it adjusts the drive as it should, but it also controls this ticking sound. The tone of the tick is effected by the EQ knobs.

I plan to replace the electrolytic caps just as a general precaution, but does this sound like an issue with the transistors or ICs, or should I wait and see if re-capping solves it?

Unrelated question: when I use the Both input, certain EQ and Level settings seem to interact and in some cases lower the overall volume. Is this normal? I wouldn't be surprised if it was some kind of phase issue or EQ curves cancelling each other out, but I'm just not sure...

[porcupine]

Played through it some more, and I'm thinking something must be wrong with the Both input. I can get a good sound through Channel A or B and set the other channel exactly the same way, but when I plug into Both the sound is substantially different. For example, if Channel A bass is set to 5 and Channel B bass is set to 5, playing through both will give a much thinner sound than playing through just A or B. Turning the bass down (!) or up on one of the channels will increase the overall bass response, but the 4-7 sweep of the pot will sound really thinned out. The mids don't behave like this, and I'll have to test some more to see if the treble is doing that. I think the pots are fine, as they work as they should through each channel individually.