Thanks Dave.
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I'll look into that next. During my initial testing I did look at the freq. output of the oscillator and I didn't see anything that looked outrageous re: actual vs. setting, but I didn't run the math to see if in spec. I the cases where the input LED was on, sometimes the oscillator freq was spot on and other frequencies where the LED was on freqs. seemed off from spec, but not too far off. I think it may be a little bit of both - notch filter center freq. being off in some cases, oscillator freq. off in others.
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I looked through the schematic at the section for the monitor output and it's a simple path from the main meter circuitry (which appears to be working) - just a resistor, fuse and then the isolation relay. I hear the relay get activated/deactivated, so once I have the unit open again I will probe that path and see where the signal stops. I am hoping that it's just the 0.062A fuse.?
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I am going to let the unit "bake" for a week or so. After 24 hours the freq. that starts requiring the vernier is now down from 3.5 KHz to 3.3 KHz.
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Did I read somewhere where HP did not include the schematic for the 339A's oscillator itself in the service manual?
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JB
