Need some help with a dead car audio amp......

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#21
Not sure why we are checking diodes here - the input diode is across the power input, not in series with it. If the amp doesn't power up, I'd suspect that one or more of the power supply transistors has a Gate short, meaning no amount of gate voltage will turn it on.

While I've never had the opportunity to repair a Butler amplifier, I've made a living reparing and designing car amplifiers and power supplies. If it seems too much for you, please consider having the amplifier professionally repaired for less than the cost of a DMM.

Regards,
Aaron

aaron@envisionelectronics.com
 
#22
Thanks for the advice and handholding. I'll check it out when I get home. There's another thought thats popped into my head that I need to check out.I'm wondering if theres a short at the speaker end thats casuing the preotection circuit to trip as soon as it powers up. I need to just connect the power and see what happens
 
#25
OK - the Subwoofer output channel is Class D made with an IR2111 MosFet Driver IC. The Mosfet output switchers should have +/- 50V on them - if not, there are many things that could go wrong here, and fixing it is not for the faint-hearted, nor for those without an oscilloscope.

The very first thing I would check is the underside of the PC board for loose solder connections. Many times - and on almost ALL early Harman-built amplifiers, the output inductors would vibrate their own connections loose. :bigeyes: The remedy is to resolder the terminals and glue the inductor firmly to the board with Silicone. Specifically check L3 and L4 for this problem.

If it's not that - I would just get the manual and start troubleshooting. I can email that to you, if you wish as it's too big to post here, even zipped.
 
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