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Old 17th November 2009, 03:40 AM   #1
AW-tech is offline AW-tech  United States
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Join Date: Nov 2009
Default Crown Power-Tech 2 repair

I have acquired a Crown Power-Tech 2 amp with blown outputs, that I would like to repair. I found some good info here about these type of amps (PB2, Macro-Tech), but still have some questions that maybe someone can help me with.

In one post here, suitable replacement transistors were lasted as follows:
Outputs
MJ15022/23
Drivers
MJE15030/31
Predrivers
MPSA42/92

I read somewhere in another forum that the original outputs are MJ15015/16. Does anyone know if this is the case? The MJ15022/23s seem to have slightly better specs. Are they an "upgrade"? Just curious.

Is it likely I will run into problems just using transistors as I get them, and not trying to match them? Never tried to match transistors before, and this would require buying more than are actually needed. The cost is already going to be somewhat high.

Also, there was mention of adding extra outputs that were not installed on the 1 and 2 models. Besides changing the emitter resistors to .27 ohms, what else needs to be added or changed, if anything? There are places for R31-34 in that area. Don't know if these are needed at all, or what their values would be.

D09-11 and Q17,Q19 have a yellowish silicone on them. Not sure what the purpose of this is. Is it some sort of thermal conductor? I need to replace these components.

Any help or advise would be greatly appreciated.
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