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Sansui G7500 HELP.

Ok....I pulled all the mentioned resistors.....all were stable except r42. It was supposed to measure 30K ohm........but never got passed 25K....and it never stabilized at a value.
r41 measured 29.6K ohm..steady. Now....I have no 30k ohmers.......will 33k do?
 
anderslober said:
Ok....I pulled all the mentioned resistors.....all were stable except r42. It was supposed to measure 30K ohm........but never got passed 25K....and it never stabilized at a value.
r41 measured 29.6K ohm..steady. Now....I have no 30k ohmers.......will 33k do?
Click to expand...

I would leave it alone (r41) - that resistor is just outside 1% tolerance :yes: - if you change it for a 33K it'll be just on 10% over :no:

If you feel you must change it, temporarily use a 56K in parallel with a 68K = just over 2% over 30K
 
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One channel first---
Verify
B+ from cap to pin 51 tied to pin 53 to collector of 2sc output
Pin 55 ties to 2sc base lead
Pin 57 from 2sc emitter

B- from cap ties between r71 and r77 0.33ohm resistors and feeds pin 59
Pin 59 to emitter of 2sa output
Pin 61 from 2sa base
Pin 63 to 2sa collector.

Please verify each wire, the polarity +/- and the color.

Pins 51 and 52 should have the same color wire, likewise pins 65 and 66. This is critical to get correct as these are the speaker output lines.

Once done compare to the other side or ask for pin outs :)
Lee
 
Overundr1 said:
One channel first---
Verify
B+ from cap to pin 51 tied to pin 53 to collector of 2sc output
Pin 55 ties to 2sc base lead
Pin 57 from 2sc emitter

B- from cap ties between r71 and r77 0.33ohm resistors and feeds pin 59
Pin 59 to emitter of 2sa output
Pin 61 from 2sa base
Pin 63 to 2sa collector.

Please verify each wire, the polarity +/- and the color.

Pins 51 and 52 should have the same color wire, likewise pins 65 and 66. This is critical to get correct as these are the speaker output lines.

Once done compare to the other side or ask for pin outs :)
Lee
Click to expand...

Are you thinking what I'm thinking Lee? Im totally convinced we have a polarity issue somehow.....
Damn thing is putting up a fight eh' ?
 
I hope this helps......please check the pics. I am staring myself blind...maybe one of you can see whats wrong..........pic 3 is good...there you can see the big caps, all the colored wires and the output config. BCE-BCE/BCE-BCE.

That is the original config. 2sc2581-2sa1106/2sa1106-2sc2581. They are BCE.
 
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anderslober said:
In post #269, pic5........the blue-orange-orange wires are on the '-' terminal of the cap on the right.
Click to expand...

From what I can see there Anders, it looks like it is wired up correctly.......
What do you think Lee?

When you power up on the DBT this time, I would leave those output boards floating where they are, making very sure they are not going to short out on anything, possibly insulate them with some cardboard or something......
Basically we dont want them attached to the heatsink this time, I want those output boards floating in mid-air, not contacting anything....

The thermal paste you are using, are you sure its not conductive?
Get some of it and check it with your multimeter.....
 
The wiring looks correct from here as well. Anders, have you checked each of the output mounting boards for shorts between the traces and also possible hairline cracks in any of the traces? A while back I had to make a transistor mounting board from scratch out of perfboard to eliminate this very issue. The more suspect of the two is the left board. Now that I think of it I think Kevzep had to do the same thing once. Although this board also had the emitter resistors mounted you can get the general idea. Not hard to do.
 

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If I have time tomorrow morning I will pull the cover off a 'G' in queue and verify each lead for you. Certainly by Sunday, day job is a twleve letter word this week. Hang in there.
-Lee
 
OK.....I think the hook-up is correct too. The paste I use(have used for years) is 'Anabond, thermally conductive, electrically insulating'......I would never use conducting heatsink paste.
I will power up on dbt with the boards 'floating'. I guess the outputs can take it for a few seconds with regard to heat build up.
 
Will it be ok to power up again....even though everything has been 'pulsed'? Basically do you think the outputs are ok? Even after the former dbt test.
 
Powered up on dbt with 'floating ' outputs.........still pulsing dbt.............

I think I'll clean sweep the outputs....................again....................or...?

I went over the 2 small boards with a loop...I couldn't find any cracks or soughts.....
 
anderslober said:
Powered up on dbt with 'floating ' outputs.........still pulsing dbt.............

I think I'll clean sweep the outputs....................again....................or...?

I went over the 2 small boards with a loop...I couldn't find any cracks or soughts.....
Click to expand...

Well, if the outputs are okay there would be no point in replacing them......man this thing is being stubborn......
There has to be something we are missing..........
 
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