Myrlynski you talked about taking out the Darlington packs and putting in 1k resistors to bypass the STK'S and perform further testing. In the schematic you highlighted what appears to be 4 resistors. Am I understanding that right.
I would connect the resistors to the four pins you highlighted and tie them in to what???
In Stereo left channel no sound. In Mono both channels have sound.
If both channels have output in MONO mode, both output amplifiers are operating. The investigation should be upstream, where the signal is split or blended ahead of the MONO switch. The prime suspect is the stereo/mono switch, and tape monitor switches ahead of that.
Would I need two jumpers per channel. One jumper on one side or resistor to pin, and another jumper on the other side of resistor to pin?
If you want the "easy" way out, acquire some jumpers with miniature alligator clips or grabber hooks, then jumper the switches at different points in the circuit.
For example, for the AUX switch L and R channels, jumper from Pins 52 (L) and 48 (R) on the board edge to R207 (L) and R208 (R). That eliminates all the questionable switches and their connections and solder joints. Plug in your source and test the operation.
If that question is directed at the resistor substitution I suggested I just removed the bad STK completely and tack soldered the resistors to the PCB where the STK pins would be soldered if it was present.
Watthour is talking about bypassing noisy/dirty switches with clip on jumpers to temporarily troubleshoot noise and/or signal loss. A different problem than bad STK units.
I was referring to what Watthour was talking about. I want to try what he said, then I will know if there is a problem with the switches or not and I can save time buy not having to take apart and clean every switch one at at time. (Note once I get the unit up and running to proper specs I can always go back and clean each switch independently. I just don't know exactly how to hook up the jumpers. For example if I was doing channel A would I connect one jumper to pin 52 and the other end to R207, then another jumper to pin 52 and the other end to the other side of R207. So I would need two jumpers per channel?
If afer this test I can't isolate the problem to the switches I will try merlynski's method. Thank you
If you want the "easy" way out, acquire some jumpers with miniature alligator clips or grabber hooks, then jumper the switches at different points in the circuit.
For example, for the AUX switch L and R channels, jumper from Pins 52 (L) and 48 (R) on the board edge to R207 (L) and R208 (R). That eliminates all the questionable switches and their connections and solder joints. Plug in your source and test the operation.
with an FM antenna connected (folded dipole or better) tune across the dial, do you get any signal strength deflection on the meter? what number? if you get no deflection you have to check that the the ckts are getting power then have to work from the RF front end thru the IF to the detector PA chip.Signal meter detect full scale with strong signal? I don't know what this means.
Since the audio problem resolved, this should now transition to the RF section.
Given that the other parts of the unit evidently had dirt/oxidation problems, it might be good to review this: http://audiokarma.org/forums/index.php?threads/how-to-clean-a-tuner-analog.144163/