I've seen a related problem with "
microplex" type systems (never
DMX) where packs from one manufacturer were mixed with a controller from another (or sometimes a new controller with old packs from the same manufacturer). This is
not the problem you're having, but your problem is similar enough that I thought I'd mention it here.
Basically,
Microplex (NSI), Microplex-128 (NSI,
Leprecon and newer Lightronics), MUX-64 (James Lighting), Sunn-Plex (SUNN Spots) and Ultra-plex (ETA) are very similar except for the maximum number of channels. Sunn and ETA felt 32 was all that would ever be needed, James Lighting settled on 64, NSI started at 64, then went to 128, and Lightronics and
Leprecon, who had started with proprietary systems, joined NSI with the 128-channel version.
In these systems the board sends data to the dimmers as a reset pulse, followed by the data for
channel 1, followed by the data for
channel 2 followed by the data for
channel 3,
etc. until it has sent out data for all the channels it is capable of controlling. Then it sends another reset pulse and starts over. There is no explicit addressing of channels.
Each
dimmer pack has a counter in it. It counts data frames until it gets to the one that matches its
address switch settings to determine which frames it should use. The reset pulse resets the counter.
But they used a counter only as big as their addressing scheme could handle. Sunn and ETA
dimmer packs can only count to 32. James Lighting and old NSI packs can only count to 64. New NSI packs, and microplex-128 packs from
Leprecon and Lightronics can count to 128.
A funny thing happens when a microplex-type
dimmer pack sees more data than it was designed to handle. When a digital counter tries to count higher than it was designed to count, it automatically resets and starts over. If a 32-channel
dimmer pack (Sunn or ETA) sees more than 32 channels of data, each
dimmer channel will try to respond to two or more controller channels -
dimmer 1 will try to respond to
channel 1 AND to
channel 33 (and channels 65 and 97 if the controller is that big),
dimmer 2 will try to respond to
channel 2 AND to
channel 34 (66, 98 ),
etc.
Unless the two or more controller channels are set to the same
level, it makes the lights flicker as they try to obey one
fader for a few milliseconds, then the other.
John