Bose amp repair

[David Head]

I seem to take on projects as they impact me. My latest is figuring out
how to repair these amps. A quick web search yesterday revealed a
cottage industry of electronic techs repairing these. Prices for the
boards run from a high of $160.00 ea to a low of 4 for $250.00 with
warrentee from 30 days to 3 years. This includes new boards ('96
models), redesigned boards with gain control, and repair of your board.
For those with Bose amps, the first thing you want to keep a listen for
is an increasing whining noise immediately after turning on the stereo.
This noise should be coming from the speakers and not the passenger
seat. This noise will eventually dissipate, but may return
intermittently (usually if from the passenger seat its relatively
constant). This indicates the capacitors are breaking down and failure
although not imminent, is coming. If the caps are replaced at this point
it should correct the problem. They are 1000uf 16 volt and are easily
found and replaced with a 30 watt soldering iron.
The failure mode as I understand it is capacitor leakage, then failure.
This causes the mosfet transistors to overpower and the IC driver chip
then fails. The caps and mosfets are easily sourced. However, the 20 pin
IC driver is a Bose part number - finding this will be the key to an
inexpensive repair.
If anyone has had a board repaired - not replaced with a new one, please
contact me. If you have amps you don't want and are willing to part with
them for little or nothing, please let me know. If I can source the part
numbers I will post the repair procedures so we can all save a bit.
If you are deciding to redo your Bose system and are wondering about
speaker replacement, its an easy procedure to bypass the amp. Stock
speakers in the back are 6x9. The factory wiring is decent although not
up to monster cable standards. A nice feature of the system is that 12
volts switched by the radio is provided via a relay to each speaker - so
if you were planning on adding an amplifier or 2 or 3, the wiring is in
4 places. Also the speaker pod in the front door is huge, giving you all
kinds of room for improvement.

Dave Head
90 V8q - 77K
90 V8q - 107K