Can you identify this Crown amp part number?

I bought a Crown D150A-II off Ebay so I could run it bridged with my D150A-II I've owned since new. It worked fine when I tested it but I never got around to setting up the two amps together, so I wrapped it up and set it aside. I recently got it out to hook up some new speakers (4412As) and lo and behold it had a loud hum on the right channel and then popped a fuse. I replaced the fuse and turned it back on without any input or output connected. The room lights dimmed and smoke came out of the right side as the replacement fuse blew. So I called a friend at a Crown authorized repair center where he works, but not on amps. He said he'd get their amp guy to look at it so I sent it up to him via another friend. They called back in two days and said it was ready and there was no charge. When I got it back the invoice said:
• replaced listed parts
• reflowed solder
• audio test: ok
• load test: ok
• checked bias and tensions

One hour labor at $75, and two part number MD21194 @ $12.00 each.
Total: no charge.

Bless their and my friend's little hearts but I'm still curious; what could an MD21194 be? Any ideas? My friend said he hadn't a clue.

Crown since 1974

Could it be a MJ21194 (output transistor)

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Originally Posted by Phil H

Could it be a MJ21194 (output transistor)

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Probably so. Perhaps a typo on the invoicing keyboard. It clearly reads MD. Since the output transistors were the original diagnosis, this seems highly likely. Thanks for the help. Today I get to see if all the smoke stays in the amp. Any guesses from those experienced pros on-board as to what causes an output transistor to go when the amp isn't even in use? Just curious since I've never had this failure before in over 32 years of solid-state amp use. I can see such a failure from maybe demanding more power than the amp was capable of producing, but sitting in a box? Certainly not something Crown's known for, as far as I can tell. :dont-know

Come on guys! It's a simple matter to go to the Crown International web site, go to discontinued products, find your amp, and go through the service manuals. All parts are listed by # there. You guys should know this.

BTW, it would appear that "M" part numbers are typically coils.

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Originally Posted by toddalin

Come on guys! It's a simple matter to go to the Crown International web site, go to discontinued products, find your amp, and go through the service manuals. All parts are listed by # there. You guys should know this.

BTW, it would appear that "M" part numbers are typically coils.

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I did not see it in the manual and the files can not be searched because they are scanned images. But, Crown also has an excel file of all of there parts. MD21194 does not exist on that list; but a seach of 21194 will yield many references to MJ21194 in the description field. The MJ21194 is a Motorola part number for a tranisitor used in the outputs of amplifiers. A blown output is consistent will the problem. Unless I missed something - it isn't that easy. But, I was bored last night so I looked around for an answer.

And I appreciate your doing so and commenting on it. I did check the information available and that includes part listings that used to be part of the original owner's manual for the D-Series amps prior to the Series-II versions, as well as on-line repair manuals offered as PDFs by Crown. That's why it was a mystery, and my not knowing an output transistor from a Pomona plug (okay, I'm exaggerating....but not by much) made the jump to a typo as the answer just a bit too much for me. Certainly it wasn't an important question but you guys are great and someone took to time to reply with useful information. If there's ever a question on some arcane topic that coincides with my limited (esoteric?!) knowledge, I'm happy to offer what help I can. But them most of you probably don't need to know the part number for the dipstick funnel that fits on the oil pump for a BMW M30 engine.

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Any guesses from those experienced pros on-board as to what causes an output transistor to go when the amp isn't even in use? Just curious since I've never had this failure before in over 32 years of solid-state amp use. I can see such a failure from maybe demanding more power than the amp was capable of producing, but sitting in a box? Certainly not something Crown's known for, as far as I can tell. :dont-know

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I'm certainly no pro, but from my experiance the fault you described most certainly sounds like the output transistor went S/C.
Unfortunatly Consumer Electronics recieve the "Lowest" end components which are poorly rated at best, you may have heard the term "Army Spec Components", & High end Commercial Components. These refer to the reliability of the component to perform in extreme conditions under constant use, amoungst other things. We will never see these components & are forced to use the not so well rated ones.
I have had brand knew Amps straight out of the box suffer the same fault you described, a combination of Poorly rated components, Poor soldering & certain climate conditions are a "possible" explanation for your fault.
Hope that helps, how does it sound, I'm already envious.

Cheers Wayne.
:cheers:

Shorted output will do it, if the protection circuit doesn't kick in fast enough....

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Originally Posted by Zilch

Shorted output will do it, if the protection circuit doesn't kick in fast enough....

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Yeah, I thought about that but I've got it running now with the same speaker leads to the same 4412As using the same Pomona plugs in the back of a PS-200 with no problem. Kind of tough to short the output with a Pomona plug I figure, even if they are those stupid glitzy Monster Cable ones from Best Buy, clad in metal. All I could find that day. I'm about to plug the D150A-II back into the system. I'll keep my fingers crossed! :shock:

(Maybe I should enjoy the PS-200 for a while longer first....?)