McIntosh MA7000 overhiting

miligor · 07:30 PM

Sorry, overheating...
The amplifier working normaly, except that one channel is very hot. Bias is 60 times bigger than bias in other channel, and I can't adjusting it. Bias adjust trimmer is on the minimum, but bias current is too high. I don't have service manual or schematic. Power transistors are Onsemi "Thermal Track" NJL3281D/NJL1302D - 12 pieces per channel. Do anyone have an idea what could be the problem here?

Edmond Stuart · 10th October 2011, 11:56 AM

Maybe Terry DeWick can help you. He's a nice guy. You can mail him at: dewickt@esper.com

Cheers,
E.

djk · 10th October 2011, 11:13 PM

McIntosh will provide a manual if you give them the sereial number.

I would check for a shorted driver or predriver.

28th September 2011, 07:27 PM	#1
miligor diyAudio Member Join Date: Nov 2004 Location: KI	McIntosh MA7000 overhiting Sorry, overheating... The amplifier working normaly, except that one channel is very hot. Bias is 60 times bigger than bias in other channel, and I can't adjusting it. Bias adjust trimmer is on the minimum, but bias current is too high. I don't have service manual or schematic. Power transistors are Onsemi "Thermal Track" NJL3281D/NJL1302D - 12 pieces per channel. Do anyone have an idea what could be the problem here? Last edited by miligor; 28th September 2011 at 07:30 PM.

10th October 2011, 11:56 AM	#2
Edmond Stuart diyAudio Member Join Date: Nov 2003 Location: Amsterdam	Maybe Terry DeWick can help you. He's a nice guy. You can mail him at: dewickt@esper.com Cheers, E. __________________ Een volk dat voor tirannen zwicht, zal meer dan lijf en goed verliezen dan dooft het licht…(H.M. van Randwijk)

10th October 2011, 11:13 PM	#3
djk diyAudio Member Join Date: Feb 2001 Location: USA	McIntosh will provide a manual if you give them the sereial number. I would check for a shorted driver or predriver. __________________ Candidates for the Darwin Award should not read this author.

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