Sansui 3000A blowing fuses?

[jleon92f]

Hi,

I have been trying to fix my Sansui 3000A that has been blowing output fuses, I changed the output transisitors on the back of the case with 4 new ones. Left channel fuses blow out as soon as power is applied?

Anyone run into this problem.:scratch2:
Any help Appreciated..
Thanks.
JOhn.

 

[jpdylon]

where the original output transistors bad? I usually won't replace them unless they are obviously shorted. Check the driver board of the effected channel for shorted driver transistors or open bias regulation diodes.

On a rare occasion, if this has been modified with output capacitors and the cap for that channel has shorted, it will also pop the fuse. However, this is very unlikely.

 

[nosirrah]

3000a

I just got one of these recently, is it possible that the trannie is shorted to the heatsink? Did you replace the mica insulators?{outputs}
Is all well with the speaker connection points?
Casey

 

[jleon92f]

I just got one of these recently, is it possible that the trannie is shorted to the heatsink? Did you replace the mica insulators?{outputs}
Is all well with the speaker connection points?
Casey

Hi,

Thanks for a reply. I do not have the speakers hooked up, I looked at the connector blocks seemed to be ok, don't rally know what to look for. The left channel was ok until I installed the new Transisitors? I am going to put back that channels transistors, they were ok before. Maybe the new HK trasisitors are bogus.

Thanks,
John.

 

[jleon92f]

where the original output transistors bad? I usually won't replace them unless they are obviously shorted. Check the driver board of the effected channel for shorted driver transistors or open bias regulation diodes.

On a rare occasion, if this has been modified with output capacitors and the cap for that channel has shorted, it will also pop the fuse. However, this is very unlikely.

Hi,
Thanks for a reply, I am going back to square one.One was bad on the right channel, now the Left channel has problems. This channel was ok until I replaced the Transistors. I will check the boards for other shorts.

Thanks,
John.

 

[nosirrah]

shorts

I'll bet you have a short to the heatsink on the outputs you installed.
Get new mica isolators, new heat sink compound {white goo}
Get trannies only from good sources, lots of counterfeits out there.
Digikey, Mouser are sources others have used here.
Casey

 

[jleon92f]

I'll bet you have a short to the heatsink on the outputs you installed.
Get new mica isolators, new heat sink compound {white goo}
Get trannies only from good sources, lots of counterfeits out there.
Digikey, Mouser are sources others have used here.
Casey

Thanks, will do.:thmbsp:

John.

 

[Duffinator]

Nice receiver built like a tank, definitely worth fixing.

Casey, I like the new avatar. :thmbsp:

 

[jleon92f]

Hi, I am back to this repair as it has been sitting in front of me all this time.

Bought new Mica plates w/ white goo on them already.

Anything I should know when replacing them?:scratch2:

Thanks,
John.

 

[nosirrah]

Make sure the transistors are not shorting to the heatsink.

 

[jleon92f]

Back on the bench..

Hi, I have this on the bench again. Got tired of looking at it .

The left channel fuses are still a problem. I get the right channel to play through headphones. Have not hooked up speakers yet.

Now the fuses are going back and forth, 1st one then the other? Both on the left channel?


IMG_0415 by jleon92f, on Flickr


IMG_0422 by jleon92f, on Flickr


IMG_0419 by jleon92f, on Flickr


IMG_0424 by jleon92f, on Flickr

I also noticed the adjustment on the PCB have been disturbed. I put them back to their original position?

Thanks,
John.

 

[jleon92f]

I have decided not to invest in this repair.. I will use the parts for something else.

Thanks,
John.