Thanks, Stan,
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I'm going through all this effort before ordering parts because it was quite a destructive event. One of the BS170's was physically broken, and the board under it charred.
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My scope is an old HP 1740A, 100 MHz. I changed probes, and now the input side of IC502 looks like a good square wave. However, the inputs and outputs of IC503C/D are not clean.? IC503A/B look okay.? I'm betting that IC503 was damaged.
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Now I'm looking at Q507. I? have read Ludwig's postings on this. With all the BS170's removed, the Diagnostics screen shows the transmitter voltage at 10.9 volts. Ludwig says it should be close to 0 volts, but maybe that is with good BS170's. The two SMPS look fine.?
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73,
Steve, N2IC
