Control/Dimming - NSI Dimmer problems

[PMWest]

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!

[jonliles]

I have to ask, is it terminated?

I've used several generations of NSI products, and have seen this type of flicker before. We resolved by hanging a dummy load on the dimmer some place where it can't be seen (like US in a corner with deep blue Gel). Leave it on all the time. NSI's are funny when the olde rpacks get to low loads, They often need more draw to keep from flickering.

You may also try using an opto isolator & translator between the ETC and the Packs. One leg to the true DMX packs and one leg with a translator to the "sort of" DMX pack.

just my 2bits (inflation has increased from 2cents)

[epimetheus]

I had a similar problem at the last church I was at. We had 2 NRD8000's and a NRD9000 all on microplex. The house lights (on the NRD9000) would flicker on occasion, but only at levels less than full. Once you bumped the channels to max they stopped flickering. I never found a solution, I just attributed it to aging dimmers. I never really looked into the microplex protocol. Does it need to be terminated like DMX does?

[TimMiller]

I have run into this before. On the express, go in to the output configuration, and see what the dmx speed is set as. I bet its set on high. Try it on normal, if they still flicker try it on slow. I bet this will fix your problem.