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Sansui g-8000 dead left channel

H

Hlash99

New Member
Hey all, I came across a mint Sansui G-8000 at an estate sale. Looks like the left channel is struggling. I tested the phono input and the left channel is very quiet, if I increase volume the unit immediately goes into Protection mode. I’ve never restored a receiver but have plenty of electronics experience…

Appreciate any help, and pointers. Thanks
 
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I’m sorry to inform you it’s probably a goner, also very dangerous to have a older stereo, not fully functioning with a possible dead channel in your house, could be a source of all kinds of problems, and would be best if you just PM me your address so I could come pick it up

:beerchug:
 
All joking aside, great pick up! Many threads / online info regarding diagnosis and repair of vintage receivers. Start with the basics. Be careful as you power up, give it a good visual, look for blown fuses, or any other obvious issues, and of course a good deoxit. Good luck!



Finally rebuilding my Sansui G-8000, I’ll post all my questions here.

Hey all, so I came across this mint G-8000 that I’m starting a rebuild on. One channel has zero output and so I’m working on finding those issues. I’m doing a full recap etc. First question: on the power supply board there is a large resistor and the manual calls for a 3.9 ohm 15w resistor. The...
audiokarma.org
 
Build a Dim Bulb Tester. (150W bulb) for starters to protect the unit from excessive current draw as you troubleshoot issues. This will protect your unit should you inadvertently make a mistake (which we all have done) when making repairs such as installing a cap or transistor incorrectly. Check DIY forum for threads on how to build and utilize. $20 insurance policy.
 
Before you do anything else, "exercise" the little slide switch on the side of the unit. It's the one that has a little plastic retainer. All the audio goes through that switch and it's notorious for causing channel dropout. If you still don't get sound, exercise the rest of the controls on the front panel. The #1 cause of channel dropout are dirty controls.

- Pete
 
LBPete said:
Before you do anything else, "exercise" the little slide switch on the side of the unit. It's the one that has a little plastic retainer. All the audio goes through that switch and it's notorious for causing channel dropout. If you still don't get sound, exercise the rest of the controls on the front panel. The #1 cause of channel dropout are dirty controls.

- Pete
Click to expand...
Thanks, yea I read up on how problematic that switch can be. I hit with some Deoxit (from the inside) and still no luck. Starting the next level of Debug
 
It's very hard to get de-oxit into that switch and it could still be dirty to the point of blocking the audio. Also, it's always a good idea to get the unit working before rebuilding. The rebuilding process is very invasive and it's easy to make a mistake. Having new problems overlapping with old problems can make it very hard to troubleshoot.

If you are getting sound from one channel, it's not in protection. That means the amp is probably OK and you should focus on the pre-amp. Do you get sound from both channels when the mono switch is on? If so, the dropout is occurring in the signal path before the mono switch. If it's still silent, the dropout could be anywhere in the pre-amp, in the connected/separated switch or in the speaker switches or speaker relay.

If you have an oscilloscope you can pretty quickly determine where the dropout is occurring. You can get a small digital oscilloscope now for about $50. It's all you need for signal tracing.

jd3rdcoast said:
Build a Dim Bulb Tester. (150W bulb) for starters to protect the unit from excessive current draw as you troubleshoot issues. This will protect your unit should you inadvertently make a mistake (which we all have done) when making repairs such as installing a cap or transistor incorrectly. Check DIY forum for threads on how to build and utilize. $20 insurance policy.
Click to expand...
A 150w bulb may not provide enough voltage drop. The higher the wattage, the lower it's resistance. On an unknown unit I usually start with 60 until I'm convinced it's stable then I switch to 100w for safekeeping. It won't interfere with the protection circuit on this model.

- Pete
 
LBPete said:
It's very hard to get de-oxit into that switch and it could still be dirty to the point of blocking the audio. Also, it's always a good idea to get the unit working before rebuilding. The rebuilding process is very invasive and it's easy to make a mistake. Having new problems overlapping with old problems can make it very hard to troubleshoot.

If you are getting sound from one channel, it's not in protection. That means the amp is probably OK and you should focus on the pre-amp. Do you get sound from both channels when the mono switch is on? If so, the dropout is occurring in the signal path before the mono switch. If it's still silent, the dropout could be anywhere in the pre-amp, in the connected/separated switch or in the speaker switches or speaker relay.

If you have an oscilloscope you can pretty quickly determine where the dropout is occurring. You can get a small digital oscilloscope now for about $50. It's all you need for signal tracing.


A 150w bulb may not provide enough voltage drop. The higher the wattage, the lower it's resistance. On an unknown unit I usually start with 60 until I'm convinced it's stable then I switch to 100w for safekeeping. It won't interfere with the protection circuit on this model.

- Pete
Click to expand...
Thanks Pete, what a wealth of good advice! It didn’t occurred to me to try mono and the implications of that. Let me give it a shot
 
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