signal tracers - remember them?

[jimh12345]

My vintage receiver has lost one channel on the Aux or Tape inputs. Weirdly, in Phono mode, I get both channels. It's hard to figure out how this could happen, from the schematic.

I don't have an oscilloscope. But back in the day, I might have used an "audio signal tracer" which was just an amplifier/speaker with a high-impedance input via a probe. I can find old ones on Ebay, but most are sold "as is". Doesn't anyone make one today?

 

[elnaldo]

Just build one probe with a capacitor blocking sny DC (I use a 1uf x 100v film cap), and one RCA conector at the other end. Then, connect the probe to a second amp.

I've posted a drawing of my probe a couple of times here at AK.

 

[jimh12345]

Good idea, thanks.

 

[elnaldo]

Good idea, thanks.

 

[jimh12345]

I figured this out and the problem is... wait for it.... yes, the volume control. One channel was dropping out above a particular level setting, which is why it seemed to be associated with only the AUX inputs. Blasting it with cleaner helps, but only temporarily.

I found one dual-gang, 100K, long shaft pot on Amazon, but no switch. I could install this new pot - if it fits, physically - but would have to add a power switch on the back panel. Either that, or give up on this receivever, having already wasted a lot of time on it, futilely trying to track down hum.

Is that pretty much the story?

 

[Pio1980]

Fwiw, one could use the good channel as the tracer, with an appropriate simple rig plugged into it's AUX line input

 

[BinaryMike]

I found one dual-gang, 100K, long shaft pot on Amazon, but no switch. I could install this new pot - if it fits, physically - but would have to add a power switch on the back panel. Either that, or give up on this receivever, having already wasted a lot of time on it, futilely trying to track down hum.

The folks on this forum have found many creative solutions over the years for such problems. Post a detailed description with lots of photos and see what happens.