Soundlab 4 channel dimmers issue

[paulthesteam42]

We have two 4 channel DMX soundlab dimmers.

 

When plugged in to either of our desks (a Zero 88 Frog,or a Zero88 jestertlxtra) I get no response.

The dimmers are addressed, and I have tried numerous different addresses.

The DMX indicator flashes but I get no response from them. The signal does pass through and the channel fuses are all good, any ideas?

[indyld]

Desks are definitely outputting the correct channels on the correct universes?

[erik10_4]

Have you tried reversing the DMX polarity? I seem to recall that some of these Soundlab units had the positive/negative DMX connections wired the opposite way around.

[xllx]

Have you tried reversing the DMX polarity? I seem to recall that some of these Soundlab units had the positive/negative DMX connections wired the opposite way around.

 

I've had a few of these Soundlab dimmers, I think there are different versions, older ones tend to have pins 2 and 3 of the 3 pin DMX cable reversed. I don't have one to hand at the moment, but pretty sure the pinout is printed on the side of the dimmer. Worth checking!

 

However, I'm not 100% certain. but from memory, the red LED flashes when they are receiving DMX, and is solid when it isn't. This suggests you are receiving DMX!

[timsabre]

However, I'm not 100% certain. but from memory, the red LED flashes when they are receiving DMX, and is solid when it isn't. This suggests you are receiving DMX!

You might be receiving upside down DMX. Depending on how the decoding is implemented in the firmware, upside down DMX can look like actual DMX with all the values at 255 (including the start code) so the device would say it is getting DMX but do nothing. Or some devices act as if all channels are 255.

 

[p.k.roberts]

If these are the black, squarish model with the four IEC sockets on the top, then I would also agree that DMX polarity will be the issue (pin 2 and 3 reversed). I seem to recall though that, rather unhelpfully, the DMX LED flashes whatever polarity the unit 'sees'. Usual safety/competence caveats apply, but it's not a major job to internally re-wire these units.

[alistermorton]

Yes, we had some of these and the connectorwas reversed. Easy enough to check - the plug and socket are connected by a PCB plug to the circuit board, and that plug can be "persuaded" on the wrong way round. This solved our problem.

[sunray]

Yes, we had some of these and the connectorwas reversed. Easy enough to check - the plug and socket are connected by a PCB plug to the circuit board, and that plug can be "persuaded" on the wrong way round. This solved our problem.

Interseting, this is not the first time the PCB connector has been mentioned.

 

I used to do some work for a guy who had loads of sets of 4 lights on bars to use on tripods or hang, each had a numbered 4 channel pack and some DMX cables were numbered accordingly. The ' numbers had been added on an occassion after a particularly fraught set up and used in that sequence since. The difficulty was adding other lights into the system. Eventually I and another had a little play and established there were something like 6 or 8 of this style of pack:

https://www.amazon.c...l/dp/B00BJLV1DO

Rather than the 'flat pack' of which about half had reversed DMX sockets, Now I don't recall if they were all Soundlab but I know he did buy them all at Maplins when they 'sold them off'. Opening the packs with incorrect wiring (and the good ones for that matter) revealed the back of the sockets encased in a hard substance blob and 3 wires from each disappearing under the pcb. I don't recall any PCB connector and found the easiest way to correct the error was cutting and joining the wires rather than trying to remove the board or the blob.

Edited November 27, 2019 by sunray

[alistermorton]

That's the ones we have, Ray.

[erik10_4]

A simple way to check for/temporarily fix reverse polarity issues is to buy one of these for £5. Saves adapting any cable re-wiring or opening the unit if your console does not have a polarity switch and is worth carrying in the gig bag anyway for unexpected situations.

[bruce]

See also https://www.blue-room.org.uk/index.php?showtopic=21919&view=&hl=&fromsearch=1

 

If I remember correctly, the screen printing on the pcb and on the casing don’t match. To make them match, the two output resistors on the pcb have been crossed, which means that the output is”correct”, according to the screen printing, but the opposite of the defacto standard.

 

On the one I had, I resoldered those resistors.

[paulthesteam42]

I am pleased to say that swapping the polarity has cured the problem,

 

Thankyou