Hi all,
I'm just "finishing" (hopefully) the repair of a 8643A signal generator, and have a few questions for anyone with a known good unit :
- does the unit warn you when you're exceeding the normal output range ? (+13dBm on the 8643A) On mine, I can punch in +19dbm and it won't complain, but looking at the scope I see significant clipping of the top of the waveform, and a spectrum analyzer also shows much higher harmonic content.
Not sure if this normal behaviour, or if mine has other issues that are not detected by the self-calibration and builtin ILD.
- how do you adjust the internal 10Mhz reference ? The instructions I found apply to the the ovenized option which I don't have...
- has anyone ever seen a paper version of the CLIP / schematics for these units ? seems awfully rare. Artek sells a copy; I haven't decided if I'll purchase that.
Actually, if someone has those and wouldn't mind looking up a few things, there's a few areas I'd like to look at :
1- charging circuit for the RAM backup battery (just to confirm what charging current they set; I replaced the battery on mine with slightly different specs)
2- STD MOD/NSM OSC module : I replaced one shorted tantalum cap in there; I'd look at how the others are used and if they're all power rail decoupling, I'll recap with alu-polymer electrolytics instead of tants. Also there was a burnt inductor that I eyeballed with a replacement but curious to see the original part specs.
Thanks !