Autotek MM4000.1D in protect mode

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These amps have a problem with breaking the legs on various components clamped to the heatsink. They often cause intermittent problems initially, then cause components to fail. An intermittently broken connection on an FET can cause the amp to go into protect but not show any shorted components when checking.

In the attached image, you can see the copper near the solder connections on Q1. If copper is showing, the terminal is broken or in the process of breaking.
 

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These amps have a problem with breaking the legs on various components clamped to the heatsink. They often cause intermittent problems initially, then cause components to fail. An intermittently broken connection on an FET can cause the amp to go into protect but not show any shorted components when checking.

In the attached image, you can see the copper near the solder connections on Q1. If copper is showing, the terminal is broken or in the process of breaking.

Ok I see what you are talking about.

Im only looking on output side or all fets?
 
All of the components are susceptible to breaking. The power supply FETs may not cause it to go into protect but if one breaks because it was ignored, it can cause catastrophic failure of the amp. The damage can be so bad that the amp will be unrepairable.

This is vibration damage I guess?
The amp was in service for 7 years before this happened.
Ill check all the legs, then if I dont see anything Ill test them.'
Then Ill post back with my findings.

Thanks for the help!
 
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