Re: DC detection circuit failure on Subwoofer
Q12 and Q13 though are the same part number, but don't need to be matched looking at the circuit configuration. You could try putting Q12 into Q13 slot and leave Q12 open (or use another cheap transistor here) to see if it works but I think Q13 slot may be a transistor killer in the long term, though the spec sheets seem to indicate the KTC2874 is a bit more robust than the typical 2SC945, 2N3904, 2N2222, etc.-like transistors which would not like being put in that kind of circuit.
So make sure you use an authentic KTC2874 if you buy one, if the KTC2874 datasheet is trustable to begin with (translation: DO NOT SUBSTITUTE IF DATA SHEET IS REAL!). Position Q12 is a bit more safe for substitution, you can use a cheap 2sc945 or something like that here instead when you borrow the KTC2874 for Q13.
Q12 and Q13 though are the same part number, but don't need to be matched looking at the circuit configuration. You could try putting Q12 into Q13 slot and leave Q12 open (or use another cheap transistor here) to see if it works but I think Q13 slot may be a transistor killer in the long term, though the spec sheets seem to indicate the KTC2874 is a bit more robust than the typical 2SC945, 2N3904, 2N2222, etc.-like transistors which would not like being put in that kind of circuit.
So make sure you use an authentic KTC2874 if you buy one, if the KTC2874 datasheet is trustable to begin with (translation: DO NOT SUBSTITUTE IF DATA SHEET IS REAL!). Position Q12 is a bit more safe for substitution, you can use a cheap 2sc945 or something like that here instead when you borrow the KTC2874 for Q13.
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