Some years ago I purchased a 494P needing repair and now finally have some time this weekend to investigate the faults. On power up it returns ROM 1 test failure. Pushing a button then completes the boot up process and the instrument appears to function in most modes, however decreasing the frequency span below 5MHz produces a 1st LO tuning failure, which is then replaced by Frequency control failure after a minute or so or when the frequency span is further reduced.
Unfortunately I don't have the extender cards (or manual), and before investing in these just wondered if anyone has any thoughts as to the best places to investigate for these errors (I'm not sure if these are separate problem, or a single problem which is associated with both the ROM and LO failures.)
Thanks for any thoughts.