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Old 15th Sep 2021, 3:42 pm   #10
Diabolical Artificer
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Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,639
Default Re: Carlsboro Cobra 1100 schematic sought

Sparks and smoke on the OP suggests shorted transistor, DC on the OP, so pull & check all transistors for SC before powering up with a current limited bench supply with the big OP transitorss removed, then follow an AC signal through to the base/s of the OP Q's before re-fitting after checking emitter resistors. Doesn't look like there's many coupling caps suggesting it's DC coupled. Without a schematic I'd go though and check all diodes too, especially that bias diode on the heat sink.

Good luck, Andy.
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