Now replace the transistors q315 and 314 ktc3815 and all the j108 is still in protected mode and change the same as a kta1504 that was in short circuit and take out the irf9640 and irf640 and they are ok and the b688 and d788 test ok without the output transistors the ampli go to green and check the feed stage all irf3205ok there is good swing rails 1 0v 2 12v 3 4.5 v
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What is the locator for the KTA1504? Q?
The rails should be +/-12 volts for preamp board, +/-30 volts? for Class A/B amps and +/- 55 volts?Class D amp. Is this approximately what you measure from speaker/signal ground?
Check the bottom side of the preamp board. The pins for the xover switch may be shorting to a speaker terminal lead that connect the preamp to main board. Also, one of the 4.7Ω 1/2w resistors may have leaned over shorting to a terminal lead.
If the above proves not to be the case try the following.
Replace all of the outputs, both Class A/B and Class D side and remove the Class D control board. Is the amp able to come out of protection? If so, the problem is most liking in the Class D driver circuit. If not one or more of the Class A/B drive circuits is bad.
Once we can isolate the problem to the Class A/B side or the Class D side, there are a few more steps that will help you narrow down further.
Replace all of the outputs, both Class A/B and Class D side and remove the Class D control board. Is the amp able to come out of protection? If so, the problem is most liking in the Class D driver circuit. If not one or more of the Class A/B drive circuits is bad.
Once we can isolate the problem to the Class A/B side or the Class D side, there are a few more steps that will help you narrow down further.
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