I have got an HP 8642B signal generator off ebay. I was hoping someone could help me to find a solution to the following problem:
The instrument gives a D75 error (test 1B of A19 module fails) at start up and when I run the Lock/Unlock test on A19 module (special code 358) it generates a whole bunch of Dnn errors (D4,D5,D6,D11, ....D34,D39,....etc)
However, I cannot detect any obvious fault or malfunction at the output of the generator at frequencies above 1058MHz. Amplitude is ok, modulation is ok, sweep is ok, etc...or maybe I am missing something?
I have the full schematics and service manual but descriptions of error codes are not in there.
Does anybody know the description of these errors or at least what they are about generally?
I have opened up modules A19A1 and A19A3 but nothing seems to be bad...the only thing I can detect by scoping around is that (only) when AM modulation is on, the ALC loop unlocks for about 55ms everytime I change output level such that an attenuator needs to be switched in/out. If no attenuator change is required, loop always remains locked. It does not seem to be unusual or abnormal to me because at those specific level transitions, when attenuator must change, the input amplitude to the module also needs an abrupt jump, so 55ms unlock seems normal to me....other than this I cannot see what these errors might be about. Is it possible that only the diagnostic reporting circuit is bad? That is just a DG508 analog switch though
I emailed Keysight for help but the person came back saying he could not find any description for those errors.
regards