# Need help on a part for an A600



## Doc ProMos (Jul 1, 2012)

I am repairing an A600 and have been chasing down a short... as I was looking I noticed that the parts in Q12 and Q30 don't match on this amp... if someone could check their amp or a schematic I would appreciate it.... mine has a MPSA06 in Q12 and a MPSA56 in Q30...thanx in advance...keith


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## ATOMICTECH62 (Jan 24, 2009)

Why do you think they should match? are they like that on the other channel?
Those two transistors are complementary bipolar transistors.They are matched pnp-npn pairs made for class A-AB amplifiers.


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## Darth SQ (Sep 17, 2010)

Send me a close up pic and I'll see what I can do.

Bret
PPI-ART COLLECTOR


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## Doc ProMos (Jul 1, 2012)

ATOMICTECH62 said:


> Why do you think they should match? are they like that on the other channel?
> Those two transistors are complementary bipolar transistors.They are matched pnp-npn pairs made for class A-AB amplifiers.


Thanx... I was brain farting.... I like a challenge but this amp has me stumped... it draws excessive current with remote power... I have checked all the usual stuff and pulled the rectifiers and it stopped pulling excessive current... I emailed Perry who thought it was inductor related but It doesn't seem to be it either.... while the transformer and inductor were pulled out I was looking around and saw the difference... but I was a bit hasty posting w/I thinking.. if there are any suggestions on what to check I would love to hear it... thanx... btw- I've checked all the audio and PS transistors and all is well... thanx....


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## ATOMICTECH62 (Jan 24, 2009)

Have you reduced the idle bias on both channels?


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## ATOMICTECH62 (Jan 24, 2009)

Also check the two large SMD transistors on the vertical boards for shorts as they are a weak link in these amps.


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## Doc ProMos (Jul 1, 2012)

I have pulled the driver boards to check them out...they were at more of an angle than I've seen in the past... I will def. check out the SMD's.... thanx...


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## Doc ProMos (Jul 1, 2012)

And I have adjusted the bias w/o any luck...


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