Driver board repair help

imraneesa

Member
2016-04-23 12:14 pm
Hi, attaching the class d driver board. All the lower supply voltages exist without outputs I have sinewave going to the driver board and pin 15 of driver board has squar wave. But no oscillations on outputs when outputs installed. Once scope probe touches audio opamp pins amp goes into protect.
 

imraneesa

Member
2016-04-23 12:14 pm
Sorry forgot to attach picture.
 

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Place doesn't matter. I tried to change Q11 and Q7 now it is working normal with all fets. These old transistors still showing like they are good with diode test with multimeter. So it is funny I dont understand.

I have been seeing this a lot lately. Transistors will check fine but the scope will show otherwise. It is a learning curve to observe, understand and analyze the characteristics of a transistor during operation under load using a scope.