DMX dilemma?

[tom_the_LD]

I see has been bought out to a panel connector - that makes sense.

 

Check for a terminator and if that isn't it then start adding things and taking things out the chain one by one.

[boatman]

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My first try would be to get the demux out of the rack and prove whether there is a terminator.

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The demux doesn't need to be taken out of the rack to see if the feed is terminated. Make sure the power is off and then check the resistance between pins 2 & 3 on the input connector with a digital multimeter. If you see something in the region of 100 ohms to 120 ohms it's terminated.

[jacet]

Handy tip, an easy way to get rid of one of your 5-3 convertors is to use the atomic. It outputs DMX on both the 3 and 5 pin connector when it receives DMX so you don't need that 5-3, just take it straight out on the 3pin.

You could even try using it as a splitter running the demux off the 5pin output and the macs off the 3pin output. I'm pretty sure that'd work. Having said that I'm not that familiar with the insides of an atomic and so don't know (/doubt) if the 2 outputs are isolated so it may not make a difference. But it might be worth a shot if you can't figure out any other way of doing it.

And to anybody who thinks this is terrible practice and that I should be shot for suggesting it... It is, but sometimes you just have to bodge something to make it work.

[Tomo]

You could even try using it as a splitter running the demux off the 5pin output and the macs off the 3pin output. I'm pretty sure that'd work.

It most certainly does not.

This would be a passive Y-split, which has numerous serious problems. The line ends up either doubly-terminated or with (one or more) massive stubs, either of which causes extremely unreliable data.

 

Some of the newer Martin fixtures have both 3-pin and 5-pin XLR connectors fitted, but they are all wired together internally.

 

This means that you can use either 3-pin OR 5-pin input, with either 3-pin OR 5-pin passthru, thus removing the need for adapters, but you cannot use it as a splitter.

[jacet]

Ah, fair enough. I had no doubt somebody would know better, I'd never tried using it as a splitter before and was unsure how they were wired internally. Thinking about it there'd be no sense in doing it any differently as it'd just add unnecessarily to the overall cost of the product... That'll teach me to post at 6 in the morning!

At least you can still use it instead of one of the 5-3s... and a 3-5 at the last Entour into the demux (if you don't go down the splitter route).

 

Edit: SPAG + clarification (posting off your iPhone is a lot harder than it looks)

[paulears]

This is exactly the kind of problem that scuppers schools who try to hire in clever kit for the occasional show. A DMX splitter is cheap, and a very handy thing to have around - AND the popular cheap ones have a 3 and 5 pin out on each of the 4 channels, meaning interconnection without adaptors easier. The fact that the basic interconnection facilities don't exist, or they didn't get the kit from a supplier who supplies a complete working 'package' is exactly why the so common cry of schools - movers - NO! is heard so often. DMX issues like this happen pretty frequently, and solving this kind of thing is day to day DMX stuff. Weird DMX problems that have amazingly simple but logic defying solutions are difficult for newbies to cope with, so getting the supplier to leave it functioning ready for programming is worth a few extra quid!

[mac.calder]

From memory, all the 250 Entours are 3&5 pin - 250+'s were 3 pin only, but I know all of our Entours are 3&5, including the pair of refurbed ones we bought as spares - so one step in simplifying the chain would be to remove the 3<>5's and link up by going in 5, out 3 then taking out 5 at the other end.

 

Not going to deal with termination - that has been covered copiously... but do check that all of your mic cables are wired 1:1 and are not phase reversed. It may sound silly, but I have had pre-made mic cable delivered with the pins swapped.

[johnhuson]

A few people seem to be getting hung up on using 5-pin to 3-pin and vice versa adapters, agreed they add to the number of connections in a system but they shouldn't be any more of a problem than any other type of cable.

 

But more to the point, if this is hired in equipment CALL THE HIRE COMPANY! Sorry to shout but seriously you're (or you're school) are paying for something which doesn't work, it may be a fault with you're equipment it may be with theirs, however any self respecting hire company will come out and have a look for you or at the very least offer you some targeted advice.

 

As you've probably gathered it really frustrates me when a hire customer returns something and says it didn't work (99% of the time not a fault on our equipment I'd like to add!) but hasn't bothered to call us and ask for help or advice. Ask yourself this if you hired a car and it didn't start, who would you call first the hire company or call a tow truck at your own cost?

[Simon Brockwell]

you could always try splitting the lines at one of the fixtures. Atomics and newer Macs have 3pin and 5pin in and out so you shouldnt need any turnarounds. Try going desk>atomic>one line to macs (3pin) one to dimmers (5pin) assuming you have some 5 pin cable which you probably dont. Thismight eliminate the reflexions problem. Also on rare occasions you will experience this type of problem if your control power and fixture power has a different earth potential.

[billy jim]

you could always try splitting the lines at one of the fixtures. Atomics and newer Macs have 3pin and 5pin in and out so you shouldnt need any turnarounds. Try going desk>atomic>one line to macs (3pin) one to dimmers (5pin) assuming you have some 5 pin cable which you probably dont. Thismight eliminate the reflexions problem. Also on rare occasions you will experience this type of problem if your control power and fixture power has a different earth potential.

This suggestion has already been made, and thrown out- there are two outputs, yes, but only one will work at a time!

[intyra]

Thanks for all your help - having tried various forms of both 3-pin and 5-pin DMX cable, the problem seems to be that the MACs simply do not like talking to the (extremely old, might I add) demux.

 

As a result, we're now using two desks - one for the MACs/strobe (a cheap chinese job, if you're interested) and one for the conventionals (Jester). It's a bit of a bodge, but it works - and that's the main priority here.

 

Thanks again for all the suggestions people have offered - if a mod wants, this thread can be closed if it holds no merit to the community.

 

Josh