Trackspot/Technobeam/DMX Issue?

[Grimtheatre]

This one has me particularly stumped. I'm working in an older theatre where we have 2 Lightwave Research Trackspots and 1 Technobeam in the air controlled through an ETC Express 250.

The DMX situation is a little funky in this theatre. There are 2 in/out boxes backstage, and one at our AP position. These all run up to the attic where they're plugged into an Iso/Opto splitter along with one half of our dimmers and plugged into the first DMX port on the board. The second half of our dimmers are plugged into the second DMX port, and the board is set to one universe, so both ports register 1-512.

A week ago the trackspots decided to take on a mind of their own, the mirror and color wheels moving even when the DMX was unplugged.

A few days ago our technobeam started behaving similarly. I went through the cues to make sure that something hadnt been accidentally recorded and found that there were values for certain control channels where there previously hadn't been. This is my first time dealing with an iso/opto or technobeams, but the profiles were properly loaded onto the board.

Any thoughts/suggestions would be greatly appreciated! Thanks!

~Grim

 

[FatherMurphy]

I think the DMX network and the fixtures themselves are not your problem, since there's no way that a stray DMX problem can rewrite cues on the console. You probably have something happening in your programming or editing sequences that is causing levels to track themselves through following cues. Is this a show that had been running fine for a while, or one you're still writing and rehearsing?

There's plenty of ETC-fluent people here who will help you straighten this out.

 

[Grimtheatre]

ADD: This is a show that's been repping with another in the same space so we've been loading different disks depending on the show. The plots (in terms of the technobeams and trackspots) are the same so no addresses are being changed. From what i can gather these are relatively older boards, so would i be wrong in considering its some sort of issue with the express then? (i initially thought it was just the trackspots being wonky, but when the technobeam joined the mix I checked the Iso/Opto splitter but there didnt seem to be a problem)

 

[DimmerDotCom]

A week ago the trackspots decided to take on a mind of their own, the mirror and color wheels moving even when the DMX was unplugged.~Grim

Problem has to lie with the opto if what is stated above is true. ARe these ETCV response opto's? If so the power supplies in these are kinda weak as the filter caps installed are fairly low spec. Fixed a couple of these units a few months ago for a major movie studio here in SoCal. They complained that between 1-3 of the outputs were flakey and such. Each DMX output has its own power supply and one was dead, 2 were going , and the remainder were beginning to show signs of increased ripple. If you have ETC response opto's give me a PM and I can help you out. Not to expensive to have someone repair and not to difficult if you have beginner electronics skills.

EDIT: or maybe not, justr re-read your first post a few more times. I read it to mean you unplugged DMX in to the opto.

 

[Grimtheatre]

Come to think of it we had just swapped out a Doug Fleenor Opto/Iso with a bad port for the ETC Response before the tech of our second show in the space, about a week before the trackspots started to go. I'll take another look at the response tomorrow. The show currently up is not the one using the trackspots so I have a little time to troubleshoot. Thanks!

 

[TimMiller]

if you have ports that keep quitting you most likely have voltage comming down the dmx line. Inside of every opto splitter, on every port there is an opto coupler that actually optically couples the input of the splitter to the output. Its job is to electrically isolate the input from the output, and it is designed to fail if voltage comes down the line to protect itself and to keep it from sending voltage out any other ports. Also every moving light and console has opto couplers internally. Its not very common to have to replace these unless lighting strikes, fixture fails internally and sends voltage down (only one i know of that does this is the atomic strobe), or something such as phantom power sent down the dmx line will kill opto's. Just an idea. Shorting usually doesnt kill them, but i guess it could happen.

 

[DimmerDotCom]

Going on what Tim said: a common way to blow ports are ground loops via the DMX shield that is grounded on both sides. YOu have the dimmer racks with its isolated transformer making its own nuetral and dedicated ground rod, then you have the console on old building power with a different ground rod/cold water pipe, then you have the convertor somewhere on a catwalk with a flakey ground. Love the possibilities. HEck, I was at a local PAC last week and actually found an open ground rod! (used a earth ground resistance clamp meter). EC said 2 out of 3 rods ain't too bad

 

[TimMiller]

With it being extremely dry nongrounding groundrods can start appearing more and more. Dirt is not the best conductor. When you drive a ground rod 8-10' in the ground you are hoping to hit some type of moisture that is down in the ground. 4-5' ground rods are completely worthless IMO.