DMX PUZZLER

[dbuckley]

No splitter I've seen needs unused outputs terminatining, it would be very odd.

 

Though on a related note; I have a four way splitter, it actually has eight outputs, a three and five pin XLR for each split, but I assume I can only use one or the other of each pair...

[Ynot]

No splitter I've seen needs unused outputs terminatining, it would be very odd.

That was my first reaction, but the manual says "The Thru and each of the output lines 1-8 need terminating"....

Unless it lost something in whatever translation it went thru... BUT for a couple of quid a plug, it's certainly worth a try!!

Though on a related note; I have a four way splitter, it actually has eight outputs, a three and five pin XLR for each split, but I assume I can only use one or the other of each pair...

Now that would be the case - they'll just be wired across in parallel, which is why you can only use one or the other on each branch.

[dbuckley]

Now that would be the case - they'll just be wired across in parallel, which is why you can only use one or the other on each branch.

You'd think, wouldn't you...

 

http://www.davidbuckley.name/pix/splitter_inside.jpg

 

Looks to me like each output is individually driven, but, they are only isolated in pairs...

 

(And yes, five power supply trannies, the input is isolated from everything, as are each of the outputs)

[JimWebber]

That was my first reaction, but the manual says "The Thru and each of the output lines 1-8 need terminating"....

Unless it lost something in whatever translation it went thru... BUT for a couple of quid a plug, it's certainly worth a try.

Now the way I read that, was that each line (1-8) needs terminating If it is used - As would be expected of any DMX line, whatever it's source... I say this, because the previous paragraph says:

 

The end of the DMX line(s) must always be terminated with a 100W

resistor connected between signal+ and signal-, this resistor can

conveniently be mounted in a 5 pin XLR plug which should be

inserted in the last unit on the DMX line(s).

Just the way I read it, of course some-one else will read the same paragraph, and decide it means something completely different... (Like a cryptic message on the meaning of Stonehenge...)

 

EDIT:

Unlike DMX, PMX may be branched and needs no termination.

Now that I didn't know...

 

Jim

[ben.suffolk]

Though on a related note; I have a four way splitter, it actually has eight outputs, a three and five pin XLR for each split, but I assume I can only use one or the other of each pair...

 

You should be able to use both of them, like I said earlier all this would mean is that the TX is in the middle of the bus. This is not the same as splitting the bus further down the line, thus making a T, which you can not do.

 

Some desks works like this. The Pulsar 108 is one that springs to mind, it has 2 outputs on it, both of which can be used, but from the same universe (Kazeja this was the point I was making)

 

Regards

 

Ben

 

Edit: Correct a Typo

[Oovis]

The end of the DMX line(s) must always be terminated with a 100W

resistor connected between signal+ and signal-, this resistor can

conveniently be mounted in a 5 pin XLR plug which should be

inserted in the last unit on the DMX line(s).

Just the way I read it, of course some-one else will read the same paragraph, and decide it means something completely different... (Like a cryptic message on the meaning of Stonehenge...)

Jim

 

Quite! I expect it means you need a 100 Ohm resistor, as is normal, not 100 Watts :P You'd struggle to find an XLR connector to fit one of those puppies

[mac.calder]

Tis also odd that they want 100 Ohm termination, instead of the specced 120 Ohm... Methinks the manual is a tad dodgey.

[JimWebber]

Quite! I expect it means you need a 100 Ohm resistor, as is normal, not 100 Watts :P You'd struggle to find an XLR connector to fit one of those puppies

I Didn't even notice that...

Mind you, the greek letter W is Omega (looks like an "Ohms" symbol), the lower case version is a "w" shape - A lot easier to type on a western keyboard... - I can find my "Euro" symbol, but the "Ohms" one completely elludes me...

 

But I digress...

 

Jim

 

EDIT.

 

I've just checked back to the Pulsar site, and discovered they have used the Ohms symbol, when I cut and pasted the text, the BR software changed it for a W.

 

Jim

[Ynot]

Now that would be the case - they'll just be wired across in parallel, which is why you can only use one or the other on each branch.

You'd think, wouldn't you...

 

http://www.davidbuckley.name/pix/splitter_inside.jpg

 

Looks to me like each output is individually driven, but, they are only isolated in pairs...

Isn't that sort of what I said...?

It's certainly what I meant!

ie - You can use the 3-pin OR the 5-pin of each branch, and you can mix the 3-pin of one with the 5-pin of another BUT you can't get away with using the 3 AND 5 pin outlets from the same branch.

 

 

 

Now the way I read that, was that each line (1-8) needs terminating If it is used - As would be expected of any DMX line, whatever it's source... I say this, because the previous paragraph says:

The end of the DMX line(s) must always be terminated with a 100ohm

resistor connected between signal+ and signal-, this resistor can conveniently be mounted in a 5 pin XLR plug which should be inserted in the last unit on the DMX line(s).

Just the way I read it, of course some-one else will read the same paragraph, and decide it means something completely different...

To be honest, on first read, that's precisely how I read it, BUT, as I also said...

for a couple of quid a plug, it's certainly worth a try!

[tij5987]

UPDATE:

 

Hi all thanks for all of your help!!!

 

Just a quick update, having included a linebacker in the DMX line (between desk and first dimmer rack) there is no change - fault is still there!!! Very frustrating so I decided to test each fixture individually. I purchased a brand new DMX cable to ensure it won't be faulty, and just to further prove that tried controlling a fixture from my other string (the one that works fine) and the fixture behaves just fine. So a good DMX lead!

 

I then ran this lead direct from the desk to the first dimmer rack and terminated the line in the out of the dimmer rack. Beaviour continued! I then repeated this process with the next fixture and it continued to cause such problems. I then repeated this process for all of the fixtures and the problem persisited along all of them.

 

Now to me that would sugest an issue with desk???

 

However, it still remains that if I put string 2 (the faulty one) into the output of string 1 the problems moves across - however no problem appears on string 1 if it is in the output of string 2, suggesting (or I might be wrong) that it would appear the desk is ok?

 

Starting to get reall bored of this now though - might try putting it all on one string and see what happens (just run a long lead from the last fixture of string 1 to the first fixture on string 2) - but after that I don't know what more I can try - The inquisitive part of me wants to find out what is causing it and I don't want to be beaten, but the other part of me thinks, not my venue, not my kit and I am only here for a few more days!!!!! Think I am running out of options - so I could always blame it on the ghosts I suppose!!!!

 

Once again, greatly appreciate all your help!

 

Tom

[Dmills]

Silly thought, but is there a cable fault floating one data line?

 

DMX will often sort of "work" single ended but will have almost no noise rejection and will tend to intermittently output garbage in this condition.

 

Terminate the line then stick a multimeter across 2&3 on the desk end of the chain... You should read around 100 -120 ohms or so, if you read >500 ohms then there is a cable fault or dry joint in one of your units.

 

Regards, Dan.

[gnomatron]

hmm, daft thought, but have you checked that the macs are in the right mode for the personality you're using? Given all the other stuff you've tried I imagine you have, but that can make them act up intermittently.

[Ynot]

Now the way I read that, was that each line (1-8) needs terminating If it is used - As would be expected of any DMX line, whatever it's source... I say this, because the previous paragraph says:

The end of the DMX line(s) must always be terminated with a 100ohm

resistor connected between signal+ and signal-, this resistor can conveniently be mounted in a 5 pin XLR plug which should be inserted in the last unit on the DMX line(s).

Just the way I read it, of course some-one else will read the same paragraph, and decide it means something completely different...

To be honest, on first read, that's precisely how I read it, BUT, as I also said...

for a couple of quid a plug, it's certainly worth a try!

Another thought that has just occurred is that we don't terminate the lines that are extended down to the stage but are not in use. Now, theoretically - like the unused ports on the splitter itself - that shouldn't be an issue because of the opto-isolation on the unit. BUT it's also something else to try, I suppose.

[tij5987]

With regards to the last but one post yes I have checked the mode of the macs, all is ok as long as my understanding that they only have two modes (normal and extended) is correct!

[noodle]

a good thing to find out is what fixtures require the 2 and 3 pins to be swapped. As the dimmer may not have to be swapped but the Macs will. if it is a fixture down the line it could be sending signal reflections down the whole line.