Broken rotary switch?

[fuzznut]

I was adjusting gain like normal when the rotary switch jammed and I heard a loud pop. It felt like some small chip jammed the switching machine.. I turned it some more and it started working. Problem is that gain does not change until step 6 so steps 1 to 5 on the rotary switch is same gain as step 6.

Is it possible that I toasted something when the switch jammed?

[fuzznut]

I'm not 100% sure if the switch was acting funny before it "jammed". I built four A12s and all of them are working fine except for that fourth one. I tried to look for bad solder joints and solder bridges but didn't find any. All of the components seemed to be in the correct places. I'll have to double check again...

[dkatz42]

Given that the gain switching is just a resistor network, it seems more likely that perhaps one of the wafers in the switch is broken and no longer engages the shaft of the switch. Some sleuthing with an ohmmeter and the schematic should tell whether each gang is still switching or not (not sure how much you can see by looking.)

Replacing that switch looks like no fun at all...