I am facing the communication errors 0075 "Bus-Comp hardware failure" and 0077 "Bus-Coll hardware failure".
It seems like a common failure, so I checked the communication cables: between the supervisor and Stereo PCBs, the cable between the Stereo and Collimator PCBs, the cable between the Stereo and Compressor PCBs, all three cables gave good continuity. The communication indicator LEDs (RXD, TXD) on the supervisor, Stereo and Compression PCBs are dimly lit, but on the Collimator PCB the LEDs are off. It appears that the Collimator PCB is bad, but the unit indicates two errors from two different devices (Collimator and Compression) as if it were a common problem on the Stereo or Supervisor PCBs.
I really appreciate the help on this. Greetings.