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Wierd dimmer and desk problems


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Hi guys got a very wierd issue which I shall try my best to explain!


At school, we have 4 Betapack 2's which are labelled 1 2 3 4 which obviously do 1 - 6, 7 - 12, 13 - 18, 19 - 24 in that order.


However today dimmer 3 and 4 swapped over.


So dimmers 1 and 2 were fine, but when I put up channel 24, instead of it putting up the last channel on dimmer 4, it put up the last channel on dimmer 3.


I checked the softpatch on the desk which was fine, and checked the dimmer addressing which was also fine.


I was using these last week for a show (I used an express for that though) and they were fine then - does anybody have any ideas?







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Now there's a conundrum... Although you appear to be running DMX, what you have is a classic problem relating to analogue systems!


Just a thought, when you removed the Express, who re-installed the Sirius? I am wondering if perhaps somebody reconnected the analogue side as well as the DMX link?


This could lead to some strange results...





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Are these Betapacks analogue or DMX, and how are you running them from the desk.


If (for example) you run Analogue for Sirius and DMX for the Express, it points to the analogue cable, two of the ways being swapped over.


If I remember rightly, Sirius's are analogue AND DMX? So if you are running analogue to dimmers, the softpatch being fine won't mean a thing. Naturally, if running DMX to the racks with the other desk, therefore not using analogue cables, this issue goes away.

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Or are you running DMX from the Sirius/Express into a Demux?


If so, have you checked that the analogue cables coming from the Demux havn't been swapped round?


IF they had been swapped round, surely you would have 1-6 and 7-12 responding to 7-12 and 1-6 etc? The issue here is the OP has problems with circuits, not racks, so likely to be the actual cable/connectors, maybe shorting or wired wrong.


Is this a new problem, or has it occurred since changes have been made.?

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Hi guys - just to clarify.


At school it's all a DMX system.


Our Sirius went poof some time ago, so this is why I got the Express 48/96 in. The Sirius today was a hired one, also DMX. However, we had this problem once before with out Sirius a while back. Can't remember how it was resolved though!

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The Sirius today was a hired one, also DMX. However, we had this problem once before with out Sirius a while back. Can't remember how it was resolved though!

If your dimmers are all DMX, with the Sirius DMX output in use, and definitely addressed correctly (as proven by another device), that leaves only two candidates: desk softpatch or internal desk wiring.


Don't however discount the possibility that somebody readdressed your betapacks when you weren't in the venue- I know there's meant to be a plate covering the address switches but they're often strategically lost.


Did you do a clear all and check the Sirius DMX softpatch afterwards? I sounds like you did, but it's of course possible that someone repatched the desk and you didn't notice it. Were you using a 1:1 softpatch of desk channels?


I made a similar and more embarassing mistake once- assumed somebody had given me a desk channel to DMX patch list on a lighting diagram- it was a dimmer channel to bar socket number list instead. Stress tunnel vision of course then resulted in me getting very angry at an innocent Jands event 408 that appeared to be bringing up random lights....


My favourite alternative theory is that somebody swapped ribbon cables inside the Sirius when assembling it. My memory says that banks of 12 faders (6 a and 6 b faders) share a ribbon cable so it would be possible to physically swap the faders for channels 13-18 and 19-24 by just putting two of the cables in the wrong sockets on the main control board.

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  • 1 month later...

Werid... from a DMX standpoint, sounds like an addressing issue.


Have you checked how the signal runs from the desk to the dimmers? Is it definitely all DMX? There's no chance that someone's stuck a demux in somewhere without you noticing, and the analogue cables have got swapped over somehow?

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Nope it's definitely all DMX.


Desk 5 pin out - 3 pin box on the wall. 3 pin box on the wall runs down the side of the hall and up into the dimmer room with a 5 pin plug on the end. This then plugs into dimmer 1 and they are chained.


I've just had a thought. Could it be a dodgey cable linking the desk to the wall? I had issues yesterday with the cable, as it was causing the DMX error and desk signal lights to stay on at the dimmers whilst the OK light flashed really fast. This also meant that channels 1 - 4 on the desk suddenly started doing the 2 scrollers as well as the fixture buttons! I fixed this by giving the cable from the desk into the box a good wiggle and made sure it was pushed in firmly at the box end. Could a dodgey cable be causing this does anyone think? I don't have another cable to try but if it's a likely I will make one myself over the hols.

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Could a dodgey cable be causing this does anyone think?


If it's a specific, repeatable and predictable problem, then it's unlikely to be the cable. In my experience of RS-485 data systems, cable issues cause all sorts of random faults, rather than a specific fault (except of course, if nothing at all is working)


If you've had the same problem with the Frog, then it's pointing more towards an addressing / patching issue at the dimmers.


One other possible cause (and I only mention it out of personal experience); has someone fiddled with the output cables from the dimmers themselves, so although the right channel on the right dimmer is being operated, it's powering a different lantern? Someone at our school decided to move a few things around one day, and it completely screwed up my plan. Twas a bit strange (during rehearsals, thankfully) when I pushed up the faders for a couple of profiles, and some red-gelled floods came on instead.


Luckily, I had also written down where the different plugs should go, so I just had to re-patch them all.

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  • 2 weeks later...

Do you have the end of line terminated to a 120 ohm resistor across pins 2&3?

Seems odd that they would transpose themselves - says either the desk is ouputting the data incorrectly (which is unlikely as you have tried more than one desk now) or the betapacks are responding to the incorrect address. Can you try the betapacks in isolation i.e. take the desk to the room, plug the board directly to each betapack in turn? You may wish to have a member of staff with you when you do this.

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