Chroma Q scroller query

[WiLL]

Ok, since christmas I've been having a bit of a nightmare with my scrollers. I have a chromaQ original Scroller PSU plugged into a nondimmed channel. One circuit has 4 scrollers and a return from the last of the four back to the return socket for that circuit on the PSU. The second circuit has an identical set-up. This configuration has worked fine for me in the past.

So I get back from the holidays to find that the PSU no longer powers up the scrollers, I get a power and DMX light on the PSU itself, but the scrollers remain unresponsive. I try all the normal diagnostics, even just trying to run a single scroller from the PSU but every time the scroller(s) refuse to power up, calibrate or scroll.

I sent the PSU off to be repaired, the service dept found one loose screw which they tightened but other than that were stumped. Meanwhile I had a hired Rainbow PSU in it's place, using exactly the same set-up and the scrollers worked fine. I got my PSU back from the service dept, plugged it in; nothing, nada, zip. Sent it back again where they ran all diagnostics, recreated my rig including the length of cable I was using between scrollers and they had the PSU working fine, so they sent it back to me.

I get it back and decide to rerun my scroller cables, plugging in each unit in turn and seeing if it powered up. It was all going well I had the 'out' run of each circuit plugged, daisy-chaining one scroller to the next, 4 per circuit. All working fine, then I put in the return run from the out of the last scroller on each circuit back to the return sockets on the PSU. Fat blue sparks occurred when the casing of the return cable brushing the metal shell of the PSU. Not good I thought, powered down, plugged up and switched back on. The first 3 scrollers on each circuit worked fine, the last one in each circuit however ( the ones which had the return to the PSU ) refused to play. Odd, I thought, as this set-up normally worked, I unplugged the returns from the PSU, powered up again and hey presto all working. Anyway, that's the rather long-winded background, my question is this;

 

Am I wrong in thinking that the 'ideal' scroller circuit should be a loop, daisychaining the units together and returning to the PSU?

[zonino]

I know that some scrollers don't like this, but I've never worked with the Chroma Q before so... have a read up in the manual

[AndrewR]

No....

 

As I understand the theory, it is intended that by looping the cables it acts the same way as a ring-main (allowing greater current load), allowing longer cable runs and more scrollers. (And also I expect terminates the DMX)

[JimWebber]

In my experience of Chroma Q's they are supposed to be cabled from the PSU, through all the scrollers, and back to the PSU.

 

Not sure what your problem is here, I would break open your cable ends, and look for shorts or reversed connections...do the scrollers indicate any form of power? (ie LED's ie DMX recieved or the fans running).

 

Trouble is, if there is a situation that creates (for example) a short circuit when the return loop is connected, it could take out a cut-out on the PSU. This would take a while to reset...

 

Just a few thoughts...

 

Jim

[merlin24]

Will,

Sounds like you could have bad/wrong cable - the case of the connector is the ground so should not spark to chassis of the PSU.

 

 

It could also be an intermittently faulty scroller causing some power issues.

 

Alternately give one of our tech service guys a call. As the distributors of Chroma Q products we do handle all of the repairs. ( Mods That was not an ad but an intended helpful comment...)

 

Just as a point it is not always that important to run a return to the PSU on shorter runs. Yes in some cases it can help data issues but not always.

 

Regards

Andy

[Kelite]

WiLL,

 

Merlin has certainly been dead-on with his comments in regards to your scroller troubles. Your question is quite valid-

<Am I wrong in thinking that the 'ideal' scroller circuit should be a loop, daisychaining the units together and returning to the PSU?>

 

No, you are right on track. The 4-pin return line will maintain the 24V line voltage throughout the system. You may not need the return if the run is short. It was mentioned, however, that the Data Termination will occur when using the return line but not without it, as the return port has a 120 Ohm resistor built into the connection.

 

(On the odd event someone runs their scrollers up to the pipe and to the PSU, they find they have power but no DMX control. Upon questioning we find no return line has been used, though the 4-pin cable being used is plugged into the return, rather than the output connector. Doh!)

 

Since the system ran fine with the Rainbow PSU, my guess is the Chroma Q PSU may have an internal issue within it.

[Tomo]

The XLR connector shell shouldn't be connected to anything, so a spark between it and the PSU chassis indicates some very dodgy wiring somewhere.

Almost certain to take out the poly-resettable fuse or even main fuse(s)

 

Check the cable is straight through and has the shells disconnected, and if the problem repeats then take the system to your local dealer/service centre to see what they think.

[Ike]

The XLR connector shell shouldn't be connected to anything...

Actually they should be connected to each other via the drain wire. Pin one is the negative supply, pin two is negative data, pin three is positive data and pin four is positive supply. All cables should be wired pin to pin with only the drain wire connected to the connector chassis.