The reason for things

[Techknowman]

Ok I got it all back together and first tested with a light bulb. then moved on to my Variac.
I got the unit to not blow parts at me or catch fire. first attempt wasn't as lucky. Took out R153-R156 and Q113.
This was due to bad diodes in the bias string.
Anyway. the bad channel now amplifies but the main transistors are heating up way,way more than the original good side.
What I have replaced is as follows.
On output board
R150, C131, Q110, Q114, Q113, CR144
On PWR-drive
U100, CR105,106,107, Q102, R112, R153,R154,R155,R156
I checked CR140 it reads the same as CR240 so I know the diode responsible for helping regulating the temp should be good.
Q110, Q113 and Q114 were replaced with MJ15024,25
On the schematic I have R153 and R157 are called out as .68 ohm units but both channels on this unit has .33 ohm. It doesn't seem to be an issue with the good channel.

[Enzo]

So it works OK but gets hot. SHort across one of the bias diodes to reduce the voltage spread between opposing drivers. SHort across CR105. ANy help?

As always, it is about circuits, it is not about parts. That dual diode does not operate alone, it is a part of a system. SO it may measure the same as the one in the other channel, but we cannot assume all the other variables are the same.

[Techknowman]

Thanks for the Idea. I didn't try it but it did lead me to the correct issue.
When I remembered that CR107 had shorted, I was unable to check R118 (18ohm).
R118 was open and thus was the issue. now everything is cool and happy.
Enzo, Thanks! you knowledge and understanding helps me think in ways i would overlook else-wise.
Where do I send the beer and girls?

[Enzo]

Send them to my shop, my wife would see them if they went to my home.

Yes, that 18 ohm parallels the diiode, and if it is open, then the full diode drop is added into the bias equation. So restoring that resistor would be similar to shorting one of the diodes.

[teamlarry]

I just went halfway through this exercise....and found that currently, GC has one advertised for $100. When does it become not worth the time?
-ls-

[Enzo]

It works in the ad, but does it work when you get it home?

[teamlarry]

Excellent point -- after 20 years in IT I should be less trusting. OTOH, my customer in this case is a pawn shop. All bets are off?
-ls-

[Enzo]

A pawn shop? I certainly don't put pawn shops very high on my list of trusted analysts of gear.

[J M Fahey]

*My* pawnshop customers ask me to "put any old worn parts in there, it must only work for 5 minutes at the shop until the customer pays"
It looks as if their only experience with service shops were with cheap car ones.
They *don't* understand that electronic parts either work or don't, and, anyway, I'm charging them for my time, not the parts.
Oh well.