Repairing a BK E-200D rf signal generator. This waveform is what my scope is showing on the output with the internal 400hz audio signal applied at 50% modulation on an approx 500kHz signal. It should be a clean sine wave. I am new to using a scope so not sure what the waveform indicates, clipping? Power supply is not clean? Here is a jpeg - thanks for any help!
It looks like your modulating audio signal is a filtered square wave (or a square wave run through an amp with inadequate bandwidth).
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The first thing I would check would be the power supply at the modulator and after. If that is solid I would then check the signal at the input and output of the modulation stage.
This waveform appears to show that the modulating signal is overdriven somewhere, so start at the modulator input and follow the signal through until you see the problem.
Good luck.
John
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