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Old 05-22-2019, 08:28 AM   #17
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Join Date: Jul 2015
City & State: Kanata Ontario
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Default Re: Crown Amp DC300A - One channel distirted, other good.

Originally Posted by Agent24 View Post
Without a scope you can use another amplifier (or build one from something like an LM386) as a signal tracer, then follow the signal through until you find where it becomes distorted.

This would work great in the preamp/input section just as a plain input.
In the power section you will need a voltage divider/clamp on the input to avoid overloading because of the high voltages. A DC blocking capacitor would be good too, in both cases. Make sure it has a rating higher than your main voltage rail value.
oops.... I needed to pay more heed to this. :-(

I was "playing" with the "DDM frequency mode"... and bad things happened when I probed from red on one of the emitter incoming lines (from the main board to amp) with black on the chassis ground.... large noise immediately...scared me and blew the fuse on the lead to the speaker.

I was expecting some sort of DC block in the meter or otherwise. Need to go back to the drawing boards and think on this a bit. I certainly don't understand how the circuit works and what to expect where.
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