Unable to tune-HED

[BCBC]

Have replaced main board, side board on a 5973A. Multiplier was also changed along with HED cable, signal cable. Unable to tune and just get noise, low values, 20 etc. no peaks. Power surge something to that effect as we powered down for Isaac and came back up a few days later. I get no error messages. Have replaced the HED supply with one from a parts instrument but don't have a new one. This inst. had the same problem in July when a power failure and restart gave the same results. Changed a few parts but never figured out what it was. Perhaps a short somewhere which reconnected. Seems all the quad contacts are tight on the board. Replaced the tune file to see if it was corrupt, this didn't help. Also changed address # to see if it was a problem with HPIB. Could there be a cable problem with the HPIB and everything look okay? No error messages etc.
Thanks

[BCBC]

Okay, have it figured out.

[West Chemist]

Sounds interesting, mind sharing what it was that was ultimately the cause of your issues?

[BCBC]

Believe it turned out to be the side door ribbon cable. Had replaced it but for some reason the replacement did not work. Helps to have a few of these anyway for other instruments.