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.