Voodoozshura You can see from page of the PDF what the different displays hp be in a working unit. Setting Observed frequency Error approx kHz Source adjustments As Manuaal said before, I was afraid of trying any test which would write on the configuration EEPROM, as I had no way to restore the previous configuration if things got worse At least now the power supply was running and I was able to check the voltage and ripple levels on the pre- and post-regulators per the Service Manual and it all looked fine. But with some determination and efforts even a very complex equipment can be repaired. That was the breakthrough and I realized that the shutdown condition was caused not by a overcurrent but by hpc undervoltage. Knowing that the analyzer seemed to run fine with an external reference was a good thing, as it really pinpointed the A3 SOURCE as the real culprit. Other smaller problem was that the power switch was semi-stuck, wth a gummy touch, making it very hard to power up and down the unit.
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The clue was something I just read on the Keysight forums - that Aha, that is also the offset of these spurs from the CW. Initially I thought my routing of the external monitor cables was the issue. Big improvement in all except the kHz spur which gets worse for some reason. The key question is does this affect the device? I have noticed some very occasional glitches in the CW signal, which makes me wonder if the spurs are high enough to confuse the phase lock.
Apart from that everything seems comfortably better than spec. Its ex Colorado Uni and by the look of the dings in it, it has taken some punishment. Pulled the cover off it - it has little plastic zip slider things, no screws.
Opened up the directional bridge and wow, it is a thing of beauty inside. Wish I had a better camera. Old repair RF input comes from the right via the choke, bottom is test port, left goes to reflected A output to VNA, top goes to termination resistor. Tiny Termination resistor at the end of the line from the Test port. Heads left via the choke to the coupler Resoldered cap visible.
Lower right is bias input.
EB5AGV's Workbench: HP-8753C repair
The clue was something I just read on the Keysight forums - that Aha, that is also the offset of these spurs from the CW. Initially I thought my routing of the external monitor cables was the issue. Big improvement in all except the kHz spur which gets worse for some reason.
HP 8753D User Manual
That oscillator is a 3. Cleaning works I have done also some cosmetic work on the unit and have also fixed the gummy power button system. To do that, I have got out the display assembly, have carefully cleaned it, and then have cleaned and greased the power button mechanism: Source adjustments As I said before, I was afraid of trying any test which would write on the configuration EEPROM, as I had no way to restore the previous configuration if things got worse But I could not find it for a while, until I got the info from another manual of an C, where it was pictured. Here you have the previous apparently good check of the YO coil drive, which showed some offset: And now this is the same signal after the pretune changes: As you can see, I was right about the offset being an anomaly. I did also some CW tests and, as a sample, a 1.
Keysight 8752 and 8753 Documentation Catalog