Technics SA-600 Receiver - Left channel problems

[Dan Rooke]

Hi all, my Technics SA-600 Receiver has a quiet left channel. To my ear it sounds as though it is missing much if not all of the high frequencies. I have to crank the balance right over to centre the sound at low volumes. At moderate volume it isn't as noticeable. Voltage bias is balanced okay. Any thoughts greatly appreciated.

 

[mbz]

Dirty switch contacts cause a lot of issues in vintage, there's a sticky on using deoxit/cleaning switches. Suggest also
check bias, procedure should be in service manual.

 

[Dan Rooke]

Dirty switch contacts cause a lot of issues in vintage, there's a sticky on using deoxit/cleaning switches. Suggest also
check bias, procedure should be in service manual.

Thanks, for you quick reply. Switches all deoxidised and bias voltage adjusted without any change. It is consistent across all source inputs and on main and remote speakers. Base and low frequency seem equal on both channels but High frequency absent on left.

 

[mbz]

Would be nice to verify a preamp issue but no pre-outs/main-in. Did you try headphones? You will probably need
some test equipment and trace the audio path, even those toy oscilloscopes (USD25-?) on the bay are helpful in such cases.

 

[Dan Rooke]

Would be nice to verify a preamp issue but no pre-outs/main-in. Did you try headphones? You will probably need
some test equipment and trace the audio path, even those toy oscilloscopes (USD25-?) on the bay are helpful in such cases.

Havent tried headphones yet but the power level display shows the left channel is down even without speakers connected.

 

[ivandezande]

Technics used certain purple caps that went bad very quickly. If it's not controls or the relay, I'd start looking there.

 

[Dan Rooke]

Thank you. I have seen that some people go as far as to replace all caps.

 

[mbz]

Maybe try checking resistance/continuity through the switches, you
can do this by unplugging the unit, select AUX, all other switches
in their normal listing positions. Measure the resistance between the
left AUX RCA inside/female to pin 13 highlighted. Repeat for right
AUX RCA and pin 10. Both results should be about the same +/- 10%?
depending on volume position.

Thank you. I have seen that some people go as far as to replace all caps.

Try and localise the problem first

 

[bhayes9614]

Hey OP did you ever get anywhere with this? I have the exact same issue with my Technics SA 600 except the right channel is low volume missing high frequencies and left channel seems fine. I have cleaned all switches and knobs with deoxit for a long time and adjusted bias. The issue also occurs across all inputs and headphones.

I'm pretty good at soldering I recapped a Marantz 2230 successfully. But finding out a starting point on this Technics is pretty challenging as I can't seem to narrow down the issue. Too add to my situation though my precious Technics SA 600 was involved in a shipping disaster with a destroyed faceplate and the wood side casings damaged. I was lucky enough to find replacement parts but only just now am finding out about the audible issues. Not really sure if it was caused from the shipping damage or what but it sat for a year after I had it professionally serviced.

Any info is much appreciated!