I received an old 8753E that was being thrown out by a telecom company and I ran into an issue during calibration. I requested some information from a company to perform a cal and they told me to check Tests 21, 22 and 17. Test 17 (ADC Linearity) fails. Going through the service manual, under power calibrations, I get stuck at Test 53. After Test 47 (RF Output Power Correction Constants), set power levels are within +/- 0.5 dB or so. Then, running Test 53 fails before I even get to test port 2. The service manual says replace the source, but as I hobbyist, I am seeing if there is a better solution.
Remind me of the name of service test 53: I think it is source power cal test. It sets power accuracy and linearity, and the linearity was quite difficult to achieve so it might fail for either port if the internal circuitry drifts out of spec. Do you have a power meter you use to run the test?