Help! Sansui G7000 !

[nadude98]

I recapped and installed new outputs in it and on initial power up dbt stayed bright, pulled the driver board and it dimmed out. Checked outputs and reinstalled one at a time and powered on. With all outputs except TR702 installed everything is fine but when I put in TR702 in the bulb stays bright..

A gentle nudge in the right direction would be most helpful!

 

[nadude98]

Nevermind...... Figured it out!!!

 

[laatsch55]

Well???????

 

[nadude98]

Well???????

Damn, sent a pic to myself of the board but it is lost in the ether. There is a resistor that sticks up in the air right next to a transistor and it had gotten pushed over into the collector of the transistor. Moved it and that problem went away. That problem anyways!

After all that I set DC offset and Bias according to service manual. Got the DC offset down to .00001mvdc! Set bias to 4.5mvdc. All with it on the DBT. After that I took it off the DBT and wanted to see if it would play, hooked up a antenna and headphones and noticed the left channel (the one I had the issue with) sounded kinda of distorted.. played with it for a few minutes and then I was going to recheck everything and I noticed the damn heatsink in back was hotter than the WOPL gets playing at high volume. I turned it off and I am done with it for the night but there is obviously something not quite right..!

Going to have to take another crack at it tomorrow...! Kinda burnt out on it at the moment. I think I've put in close to 30 hours on it over the pastr 4 days.

 

[stuwee]

That's a nice receiver, worth spending some more time on, hopefully you'll get some info on what's going on with it!

 

[Elite-ist]

I hope you can get your Sansui receiver all figured out. Had you owned it for long? I recently put my Sansui G-5500 up for consignment sale at Innovative Audio. I was the second owner of the receiver. When Geri and I were married last August, I used it as a back-up receiver for our wedding reception held at the Legion. I supplied my own stereo system and music during our dinner and reception/dancing. I was nervous about using old equipment, but everything worked great and the system played practically non-stop from 6:30 p.m. until 2:00 a.m..

​

Nando.

 

[nadude98]

That's a nice receiver, worth spending some more time on, hopefully you'll get some info on what's going on with it!

Yes, it is... I got it done and sounding awesome. It was bias setting and a bad driver on the board. Replaced all the drivers on the board with new transistors, and after that I was able to get the dc offset down to 0.0002mv

Played it for about 4 hours and now it's ready to go home for hopefully another 40 years of faithful service to music!

 

[nadude98]

It's not mine. It belongs to a good friend of mine.. he bought it new when he was in the Navy. We're redoing it to power the Altec Model 14's he just bought.

 

[nadude98]

Well, when I took it over to his place and we hooked it up to his Altec's a issue came to the surface.. I guess it was a heavier load than I had placed it under and it seems like the right channel is a tad weaker than the left.. any ideas.

 

[nadude98]

Right channel is definitely lower output than the left, also have left channel cutting out. I believe one of the 2SK109's are failing.. Tried testing it but not for sure I am doing it right.

 

[Elite-ist]

Does anything change when you slightly turn the source selector knob? Sometimes the source selector knob needs cleaning and lubrication to prevent channel cut-out or distortion.

Nando.

 

[nadude98]

Does anything change when you slightly turn the source selector knob? Sometimes the source selector knob needs cleaning and lubrication to prevent channel cut-out or distortion.

Nando.

I'll try that... Cleaned it once, but sometimes I know it could use a second try.

 

[nadude98]

Does anything change when you slightly turn the source selector knob? Sometimes the source selector knob needs cleaning and lubrication to prevent channel cut-out or distortion.

Nando.

Did more cleaning of all the controls.. also replaced all the MV12's with dual 1N4148's. Now balance is even but it's still distorted and won't hold consistent offset..?

 

[nadude98]

Got it all pretty much sorted out, or so I thought... now just have a loud popping or thump when I switch source to phono 2. No sound from left channel phono!

 

[nadude98]

I'm getting 30vdc positive and 33vdc negative on the rails for EQ board. I'm not confident on trouble shooting the power supply, at least for the 30v section.. Should I be concerned about it?

 

[nadude98]

I'm getting 30vdc positive and 33vdc negative on the rails for EQ board. I'm not confident on trouble shooting the power supply, at least for the 30v section.. Should I be concerned about it?

Bump!!! Best opinion's?

I have been through everything as best I can and can find a bad component in the power supply... schematic attached
View attachment hfe_sansui_g-7000_701_schematics.pdf

 

[nadude98]

 

[Northwinds]

I think the lack of helpful responses is because nobody messes with Sansui gear here really. You might jump on AK and post a thread in the Exclusively Sansui section, should get lots of help there

 

[nadude98]

I think the lack of helpful responses is because nobody messes with Sansui gear here really. You might jump on AK and post a thread in the Exclusively Sansui section, should get lots of help there

 

[orange]

Sansuis obey the same laws of physics and amp design as most any other make.

Sometimes it's a little busy here or maybe we just haven't looked at the thread lately.

If you have an intermittent channel I doubt the power supply is to blame. Try your switches, then work through the affected channel's circuit path. If the channel intermittency seems to be relate to temperature, isolate the bad part and replace.

My G-5700 has two separate output boards, does yours? Have you checked the solder joints to and from them, and checked to see if moving any of the wires makes or fixes a short (cracked wire)?

Do you have internal fuses on the boards? Are any blown (my experience with the X0X0 and earlier series)?