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-   -   transistor for CROWN amplifier (http://www.diyaudio.com/forums/parts/111712-transistor-crown-amplifier.html)

tom31415926 11th November 2007 12:27 AM

transistor for CROWN amplifier
 
Greetings,

I am repairing a CT800 Crown amplifier. I have found a bad transistor that Crown calls a C 8187-4. A number of power transistors are in parallel, with emitter ballast resistors, but even so I think they pre-sorted for matching since there is a "3" stamped on the case for all of the devices that are in parallel.

My search on this site suggests that some wold use the MJ21193 from ON sumiconductor (and its complement) for this application, but it is not clear that the person posting was replacing exactly the same part as I need to replace.

Does anyone know of a generic number to replace this transistor? (it is in a TO-3 case). I would obtain a few transistors and then hand match to the good ones that will be re-used.

this transistor is an NPN power transistor. If you also have any information on the PNP parts, I'd be interested in that also, since I haven'c checked all the PNPs yet.


thanks !

Tom

tom31415926 11th November 2007 12:42 AM

I just noticed that the MJ21193 is the PNP; of course the NPN MJ21194 is under consideration for replacing the CROWN C 8187-4.

thanks,

Tom

taj 11th November 2007 04:57 PM

Do you have a schematic? I'm not familiar with that amp, but it's probably worthwhile to look at the schematic to at least ensure it doesn't use FET's before recommending a replacement BJT.

MJ21193/94 are very good BJT's, as are MJ15024/25. Chris ('Anatech') :worship: would probably have the answer for you in 2 seconds.

..Todd

tom31415926 12th November 2007 04:44 PM

Thanks, Tod.

Yes, it is a BJT. I was able to find a schematic online. I usually just check BJTs to see if they look like two diodes, and this one has a very low-resistance junction that conducts in both directions, so its bad.

I'm beginning to think that if I don't have access to the CROWN specifications, and I replace with a new type part, I should replace all three paralleled transistors with hand-matched parts of the new type.

We'll see if anyone else adds to this thread, otherwise, that's what I'll do.

Tom

taj 13th November 2007 03:44 AM

Yes, yes, yes. If you have to change part numbers, you will need to change all of them, including its complementaries. That much I do know.

..Todd


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