POP-POP-POP-POP?

In a "junk" pile I found a curious looking amp. I powered it up and seemed to work for a while but now one channel keeps going POP-POP-POP at about 2 second intervals.

Other than the huge PS filter caps, it uses no polarized capacitors--just about 8 bipolar lytics and the rest polys. It has 8 MJ21194 power transistors per channel, and various general purpose transistors throughout the circuit.
I haven't really run into any bipolar lytics until now...
What's more likely the culprit, leaky caps or an output transistor?

Motorboating ?

I've seen a cold solder joint on a transistor cause that - is it in both channels? If it is, then its easy to determine where the problem may be. If its just one channel - well thats even easier cause you can use the working channel to compare the broken one with.

> What's more likely the culprit, leaky caps or an output transistor?

Caps. Transistors don't do frequency.

I had that problem on one of my ampex machines. The loud pops were generally caps but the low level popcorn towards the noise floor turned out to be a swithcing transistor that somehow was getting into the audio path. That took a while to find.

dave

Whwnever I hear POP-POP-POP I just write it off as the hood. :grin: