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WHAT WOULD CAUSE JC-1 MONOBLOCK TO SELF DESTRUCT?

Hi all,
I own Parasound Halo JC-1 monoblock amps, and have never had any reliability issues at all with them.
I have a friend, however, who had a JC-1 monoblock to literally self-destruct.
He said he was listening to it at normal levels, and heard a loud pop that almost sounded like a firecracker went off, the amp went completely dead, and the smell of toasted components filled the air.
He shined a flashlight through the top cover and said that it looked like at least 8 to 10 of the black square Sanken transistors mounted on the sides of inside of the amp, on the heat sinks, had literally blown to pieces!
He said the Sanken devices were still there, but the centers of many of them had literally blown out.
I would assume that these square black Sanken devices are the output transistors?
He checked the power cord, speaker cables, speakers, interconnects, etc., for short circuits and found nothing!
Has anyone else out there had this to happen to their Parasound Halo JC-1 monos, or any other amp before?
What would cause such an incident to happen?
Any answers, ideas, or help would be greatly appreciated.
Thanks a million!
Angela
audio_girl
metralla
945 posts
 
Thanks for posting, Richard.

Regards,
matrix
305 posts
 
First thing I came up with was one transistor not up to par, before reading all of the posts. can almost guarantee thats really the only thing capable of that unles a ground or power wire came lose and shorted, but common whats the chances of that? It had to be a shorted transistor from overheat or something, maybe not in perfect contact with the heatsink, they use a grease kinda stuff to make contact, something happend.
audio_girl OP
91 posts
 
Guys,
Thanks for all your replies!
My friend has his JC-1's plugged directly into dedicated outlets.
Unfortunately, he bought the units used about 15 months ago, so there is no warranty on them.
He did have this amp repaired by Parasound in July 2005.
He accidently dropped an interconnect on the speaker cables where they exit the amp, and it caused a short circuit and they had to replace all the output transistors, mosfet drivers, fuse, some resistors, emiter diodes, etc.
This time, however, he did nothing wrong...the amp just self destructed.
He also said that the amp hadn't acted completely normal since it was repaired. He said it would shut itself off occasionally for a few seconds, then resume normal operation. He said when it would do this the blue halo light around the power on button would turn red.
He said this would happen up to 4 times per hour on certain days, and was totally unpredictable.
Thanks again for all of your responses!
Angela
bignerd100
515 posts
 
The Parasound amps do have a protection circuit for extreme low impedances (as in a damaged speaker). This will turn off the unit before blowing up (usually). If your buddy blew it up once then there are probably parts that sustained damage but tested ok at Parasound. THese parts were likely starting to give out before the thing finally blew up (again). It has been my experiance that once an amp has been blown up it will never be the same unless you replace everything inside the chasis (in which case you might as well buy a brand new unit).

I guess that the 10-15% discount from retail that the average retailer is willing to give looks good after buying used, repairing used, then having to decide if repairing used is worth it the second time. Not trying to add insult to injury but sometimes it is better to drink fresh beer than second hand champaign.

Sincerly, good luck to your buddy. Having big $$$ go up in smoke is tough.
seadogs1
104 posts
 
Perhaps it's time for Mr. Curl to enter this. I too have the shut down problem for seconds at a time then everything is normal. I think it may be connected to the protection circuit of the amp except there is no reason it should be kicking in. Any thoughts by John would be much appreciated.
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