Technics SA-616 Tape 1 and Tape 2 left channel not working

[David Brehm]

Just getting into stereo vintage repair. My receiver just went out, the Technics SA-616. Here are symptoms:

It was working fine for the last 2 months. Now the left channel does not work on Tape 1 or Tape 2. I would like to use an equalizer and I cannot get the left channel to work any more. I swapped out the equalizer but I get the same behavior on both Tape 1 and Tape 2.

For the last two weeks I could turn the power off and turn the power back on and the left channel would sometimes click in and work and be ok after the speaker protection circuit clicked from "protection" to "safety".

Any help would be greatly appreciated. I have a scope and signal generator so I thought I would work through the boards and see where the issue is...

Regards,

David Brehm

 

[century tek]

Does AUX, phono, AM / FM work okay?

The first thing I would do is to clean all your pots and switches. If the symptom still persists, then it might be something else like pitted contacts on the protection relay.

If you crank it up for a second and it pops back in, then yup, relay contacts.

 

[David Brehm]

The AUX is now having some distortion on the right channel. Tuner is fine. I had this before, cleaned the pots and switches with DeOxit, and it cleared this up. Maybe a second pass cleaning first and then looking at the contacts for the protection relay.

Thank you for your help....

 

[century tek]

 

[David Brehm]

I have cleaned up all the pots and switches. The Tape Monitoring switch is the culprit on the Equalizer Circuit board. I put deoxit in it and it lasted about 3 days. I was about to close it up and the left channel went out again. I simply press on the plastic switch on the board and it comes back. I have tried resodering the connection mounts but this did not seem to make a difference. My next step is to take the board out and carefully use deoxit all over the switch with a Q tip.

Any other suggestions are greatly appreciated...

 

[century tek]

Replace the switch.

I swear to goodness that tape monitor switches seem to give the most grief!