G-8000 In Protection Diagnostics

mikte15

Active Member
ATTN - Sansui Techs

We have a receiver in protection and fiddling with VR01 & VR02 is not helping.

We want to check DC above protection. Is that checked with meter at pin 13/14 and ground?
 
ATTN - Sansui Techs

We have a receiver in protection and fiddling with VR01 & VR02 is not helping.

We want to check DC above protection. Is that checked with meter at pin 13/14 and ground?

Correct, there is rather confusing pin labelling in this area of the schematic, pin 06 is the output pin of the driver board, connecting through F-2814 onward to the output transistors and the centre junctions of the emitter resistors, the traditional measuring point for an amplifier of this type with protection activated. (pin 13 on one channel and pin 14 on the other channel... allegedly).
 
Thanks John!

I'm having difficulty understanding where Pin 13 & 14 are, on the F-2809 board?
 
Might consider pulling the output transistors before continuing with readings--
-Lee


Funny you should say that.

The owner of the receiver took it to a local tech this past week and was told the outputs were shorted and the amp boards have to be rebuilt.

My question to my friend was how did the tech know they were shorted.

Undoubtedly that's the issue you're warning about.
 
I'll add here that I did not touch the receiver myself. All our conversations about it were by phone.
 
The owner of the receiver took it to a local tech this past week and was told the outputs were shorted and the amp boards have to be rebuilt.

I sure as heck wouldn't have fire it up until the outputs are checked/replaced and the driver boards fusibles have all been checked/replaced.
 
I'll rephrase my question above.

What is the simplest/quickest way to determine the outputs are blown?

Pull them and test?
 
I'll rephrase my question above.

What is the simplest/quickest way to determine the outputs are blown?

Pull them and test?

Correct, you must test each one 6 ways, that is each of the three junctions in forward and reverse directions, and this should be done with your multimeter set to the 'diode test' position. You must avoid touching the transistor terminals (ECB) as you with then read the resistance of your fingers/hands as well as the junctions.
 
There are NPN and PNP outputs. They need to go back in the right place. Either mark the heat sink or pull and test them one at a time.

- Pete
 
they will test short in circuit if they are ..BUT need pulling to test again as if they test ok then find the shorted power supply or driver transistor etc ..if shorted still test everything else ...
i am not sure if outputs randomly short under normal use but if they did more damage will likely occur ...
if you can find the in detailed history of the unit all the better in a diagnosis .
one example ....it was fine until i shorted the speaker terminals .
 
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they will test short in circuit if they are ..BUT need pulling to test again as if they test ok then find the shorted power supply or driver transistor etc ..if shorted still test everything else ...
i am not sure if outputs randomly short under normal use but if they did more damage will likely occur ...
if you can find the in detailed history of the unit all the better in a diagnosis .
one example ....it was fine until i shorted the speaker terminals .

The owner, a friend of mine, stated that he had just acquired a new set of Sansui speakers and had listened to them briefly at moderate levels before going into protection. He did not have or test with an ohm meter before trying the speakers.

I got interested in helping him out because I also have a G-8000 sitting in my audio rack waiting for me to do a total rehab.

I think he plans to sell unit because he doesn't have the knowledge or patience to rebuild the it. The tech wanted a lot to fix it.

I looked for replacements for the outputs anyways because I'm interested.

The stock Sankens (2sc1403 & 2sa745 I believe) look like they could be replaced with OnSemi MJ21193/4's. Does anyone concur?
 

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The stock Sankens (2sc1403 & 2sa745 I believe) look like they could be replaced with OnSemi MJ21193/4's. Does anyone concur?
Have you tested the Sankens yet ? Or you just planning on shotgunning it ? Yes, those Onsemi's will be sufficiant. MJ21193G and MJ21194G.....
 
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