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Coemar 250 wash light


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I powered up the 4 of these I leave in my venue permanently - been there 10 years now, and have always been good - and one seemed to be misbehaving, so I took it off the truss and opened it up. The fault is that the dimmer, the shutter, the CMY blades and beam shaper all jitter as soon as a they are taken from the start position. So bringing up the dimmer means it continuously cycles from maybe 25% to 75%. The CMY steppers do the same thing as soon as they're moved away from white. Beam shaper and shutter starts to jitter wildly as soon as they're introduced.


Putting the unit into manual mode produces absolutely normal smooth movement. You toggle to dimmer, hold the button in and it smoothly opens up. CMY, shutter etc all operate normally. Demo mode does too. However, give it some DMX and everything jitters really badly.


Does this ring bells with anyone? I'm guessing that it's probably a proper fault in the DMX input stage, before the manual control stage?



Any suggestions would be appreciated. The fixture is one of those made by Robe, badged by loads of people when it was new.

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It does sound like a DMX issue, rather than a motor driver issue. If its the same as the Futurelight MH640, then the DMX is first processed by the cpu in the display board of all places. This board communicates via a ribbon cable, and if some corrosion has got in somewhere then that might explain the jittery DMX. If you need any bits, assuming your unit is the same as the MH640, then let me know. I've got a couple of semi-complete units that I want to get rid of, as well as several PCBs.
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