1756-DHRIO Problem

I have the above card series D in a 10 slot rack. Oddly enough every so often it seems to lose its connection to the main trunk on DH+. The RIO(channel B) still seems to function but the only way to get this functioning again is by recycling power to the processor.

Has anyone run into this problem or know of a fix that might alleviate it?

I've found that the DHRIO is EXTREMELY picky about having the proper terminating resistor installed - especially if the DHRIO is located at the physical END of the blue hose ... other DH+ stations (PLC-5, SLC-5/04, etc. don't seem to be so fussy) ...

specifically, sometimes I've plugged a PCMK cable into a DHRIO (8-pin mini-DIN plug) and couldn't communicate - UNTIL I installed a spare 3-pin plug with a resistor on it ... in other words, if the PCMK cable was the ONLY connection to the module, I couldn't communicate reliably without providing the termination resistor ... I've never had a PLC-5 or SLC-5/04 act that way with a PCMK cable ...

so ... have you checked the resistors lately? ...

This card is in the middle of the trunk. The trunk does have PV600's, PLC5's and SLC's as well.