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Four track cassette no signal output on channel three

lukelafayett

lukelafayett

LUKE
I need some advice trouble-shooting an analog circuit on a four track cassette recorder. There is audio output from the cassette playback head but once the signal enters the PCB board it does not come back out like the other three channels. Mostly all I see on this PCB board are capacitors and resistors. I see no damaged or blown out components.

How do you trouble-shoot the components? ESR meter for the capacitors? Oscilloscope for the circuit?

The machine is an AMR MCR 4 made by Peavey back in the late 80s.
 
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If the PCB traces are accessible, it should be fairly easy to follow the signal from where the head input connects using a scope, until you lose it. Then check the components around there. Are any of the caps electrolytics? They would be my first suspects. They won't necessarily show any external damage, especially smaller ones.
 
swechsler said:
If the PCB traces are accessible, it should be fairly easy to follow the signal from where the head input connects using a scope, until you lose it. Then check the components around there. Are any of the caps electrolytics? They would be my first suspects. They won't necessarily show any external damage, especially smaller ones.
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There are about a dozen electrolytic caps and a few "orange drop" capacitors that we call them in guitars.

I know how to use a multimeter and and have replaced numerous solder components but not an oscilloscope. Is is worth getting an oscilloscope or should I just get an ESR meter to test the capacitors?
 
You can get a cheap scope (either new or used - I have an old 15mhz TV serviceman's scope from the 1970s. You won't need higher unless you're working on digital circuits...or maybe radio tuners) but it might only be worthwhile if you plan on servicing other components in the future. I'm not sure an ESR meter will help as I've never used one.
 
You can trace a signal with a DMM (if you play a 50 or 100Hz sine wave, any decent DMM set to AC should be able to measure some AC mV) or with a signal tracer probe, sending the signal to an audio amplifier, even a cheap powered speaker will serve this purpose.

sonda_audio-2.jpg
 
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