Blinking lights


I am running Unison 24 Dimmer rack to our circuits in the catwalk and also run Socapex from a 12 Dimmer portable rack. Whatever lights are running through the portable dimmer occasionally blink. It's pretty random and real quick...and very distracting. We just got the portable dimmer about 6 months ago and when powering it up, the only power left in the building (an old movie theatre) was to pull from the same power that powers our amps. So I think this is a power issue, does anyone have any suggestions? Is there anything I could add, besides pulling more power into the building, that could stop them from blinking?
There are quite a few things you hould check:

1) Your control cable. Is it DMX? Does it dasy chain from another dimmer pack? If so does that pack blink? Do you have to control cable close to and computers or any other electronic device?

2) Does the dimmer pack your having problems with have a DMX terminator on the out end if your not using it?

3) Do the lights blink when large amounts of bass or any large amount of sound are produced by the amps?

4) Is the pack overloaded? (Not per dimmer but total watts for the pack.)

5) You need to put a multimeter across the power supply for the pack. If you under 110 you may want to check the resistance on the feed for the pack.

6) A weird problem I ran in to was a large voltage drop when an HVAC system kicked on. Check and see if this happens at set intervals or if you can hear HVACs coming on...

My first instinct would be to check the control cable.

Hope that helps.

1) The control cable is hand I can't remember if we daisy chained it to the other rack...if it is, the other rack doesn't blink. Our racks are in a little back room off of the catwalks...the heater/ac unit is on the other side of the wall that the racks on mounted on. The room they are in is also an office which has a computer, etc. in it.

2) Need to check on the DMX terminator...not sure.

3) I haven't noticed any connection to the lights blinking with large amounts of sound. The seem to blink pretty randomly...sometimes during a loud song, but also just when there is one person on a lav.

4) I'm pretty sure the pack isn't overloaded, currently not using all 12 dimmers and there is only one light per dimmer.

5) Might be a stupid question...but what's a mulitmeter?

6) Haven't noticed this...but will look into this...

Thanks a ton...if it is the control cable that is causing the problem, what would you suggest that I do?
If all the lights on that pack blink at the same time, I'd look at a problem with the power to the pack or a fault in the pack itself. DMX-512 is a pretty robust system - the protocol requires a dimmer to hold its last value for at least a full second if the DMX signal goes away, making it unlikely (but not impossible) that an intermittent interruption from a bad cable would cause the lights to blink. If it's a bad cable, it might cause different lights to blink at random by corrupting, but not interrupting, the data. If it's a missing terminator, it will most likely affect all the packs in that universe, not just one.

The lights do all blink at the same time. It's really quick and they'll even do it when the amps aren't on. I can try cleaning it, but we've had this problem ever since we got the pack, so I'm not sure that will fix it. I'm starting to wonder if it's a faulty pack. If it were an issue of the power to the pack, it seems like it would be fine if the amps were off, but they blink either way...
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.


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