I have obtained a very cheap HP8664A, but, of course, with issues. Ser no starts with 3744 but internal date codes show well into 2000. It has options 010, 004 and an oven. It has a special high shielding case. Each time upon power-on it will calibrate itself, a long operation. Then it will give the Result code: 3,504,311. MSSG gives: Hardware Failures; 5 and 1 and Calibration Errors: 2 and 1. The repair manual I have suggests to look at A10, the fractional N module. I opened it and found a beautiful pcb without any visual or smelling anomalies. The power supply is fine. On my SA (HP8562A): between about 400 MHz and 2.9 GHz everything is fine. Nice clean stable signal, frequency and amplitude spot-on. Can be modulated as well. Outside this range the signal is clearly out of lock=useless. I checked the Eeprom (28HC64) at the interconnection board and it reads fine on my Eprom programmer.
ILD test 320 gives the code; +3,504,311, quite similar to the calibration routine. The HW Failures and Calibration Errors given above can not be found in the manuals I have.
Any help in bringing this beautiful instrument back into service is highly appreciated.