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Old 01-09-2013, 10:11 AM
stuartjohn24 stuartjohn24 is offline
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Location: Chippenham, Wiltshire, UK
 
Join Date: May 2011
Posts: 664
Mein Auto: BMW E65 745i
Pulled the AMP last night, looped the fibre bus and idrive is now working correctly and I have sound again! (Sounds completely crap as expected!)

Anyway took the amp apart to see if I could identify anything obvious.



Caps don't look suspect visually, which I kind of expected as it was working perfectly up to the point when it suddenly failed.

I will get the caps on the ESR tester at work to confirm if they are good or not.

Interestingly the amp has already been replaced at least once, this one was made in Q1 of 2006.

Upon closer inspection the amplifier PCB shows evidence of water damage, this has caused corrosion between the pins of the IDC board connector.





The symptoms I am having is resetting of the MOST bus every second or so, with audio only coming out of the speakers driven by the ASK unit (front door mids and tweeters, and the rear mids) also after removing the key from the ignition the MMI will stay powered and not shut down.

The amp is constantly interrupting the MOST bus as if the MOST controller is continually resetting. This leads me to believe the amplifier part is ok and it's a control issue, which almost certainly means a new amp!

I have been inspecting the controller PCB and I have noticed a Maxim watchdog/brown-out supervisor IC, I'm wondering if this is what's resetting the controller every second because of a low supply voltage condition possibly caused by the corrosion on the board connector?

I will power it up on the bench and get a scope on it see what's going on tomorrow, clean up the corrosion and hope it sorts it out!

I will update on progress for those of you interested, may be useful for some of you.

Stuart
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