HP 8753E Service Manual page 234

15. On the spectrum analyzer, set the center frequency for 676.003045 MHz.
On the HP 8753E, press (Menu) YmFY$$Q. c-1 m.
17. Adjust the API4 (R47) for a null ( minimum amplitude) on the spectrum
analyzer.
18. If this adjustment cannot be performed satisfactorily, repeat the entire
procedure. Or else replace the Al3 board assembly.
Adjustments and Correction Constants
3-57