Here's an odd one: We have a mixed rack of NSI dimmer packs: 2 NRD-9000s (8x 2.4KW), 2 NRD-8000s (8x1.2kW), and 4 NDS-12s (12x1.2kW). The NRD units run on Microplex control through an NSA DMX-MPX adaptor. The NDS units run DMX control. The whole thing is controlled by an ETC Express. Here's the problem: when a cue with low levels on all dimmers (10-15%) is run, a manual override (bringing up a channel slider) causes the lights on the NRD-9000 dimmers to flicker up and down slowly. The system is lightly loaded, maybe to 50% of capacity. The console checks out OK. DMX cables are OK. The mains voltage to all the dimmers is steady. No overtemp lights are on. MPX control status is OK. This is a new one on me. The NRD-9000s are old (1992) so it may just be a dying firing card. Any ideas about what's causing the problem? Thanks!