Pulsing Lamps

[jason.fallon]

Hi All,

 

I'm having a bit of an ongoing issue and I'm just wondering if anybody else has experienced it. I do a lot of lighting in community hallsand school halls. I'm using 2 Showtec DigiDim Basic 12 (http://www.highlite.nl/index.php/highlite/silver.econtent/catalog/highlite/entertainment_products/showtec/lightcontrollers/dimmerpacks/digidim_12_basic) and a Zero88 Leap Frog 48 to control.

 

Lately the lights have started pulsing. If they are at 100% they will pulse dimmer and if they are off they will pulse to about 10%. Its not happening with the movers so my reckoning is that its an issue with the dimmers or the way the desk talks to them Has anybody experienced such an occurance in the same or similar circumstances?

 

More info:

 

Dimmers running on Single phase supply of 63A each. (both on different phases)

2 DMX lines in use, 1 for dimmers + foggers, 1 for Movers

 

Any ideas would be greatly appreciated

 

Thanks

 

Jason

[Ynot]

Usual suggestions to begin with.

 

Check all cables (by substitution if necessary) for wear/damage.

If using different cables at different venues make sure you don't have a reversal cable in there somewhere - that can do strange things to dimmers.

Try using the other DMX output and see if the problem remains.

Try terminating the end of the run. Lots of discussion already this week on whether it's necessary, but never hurts to try! :D

Take the dimmer and a lantern right to the desk and connect using a known working DMX cable - see if the fault occurs there. If not then you have an infrastructure problem - dig deeper. If it does, then your desk is likely at fault.

[david.elsbury]

Is this at particular venues, or all of them? It might be the power? My church has some funny, funny stuff going on with its power which I still haven't figured out. And I've often had this on generators with an AVR that can't cope...

[adam2]

As suggested above, it might be a problem with the mains supply, try connecting a lantern direct to mains (useing a 13 amp plug to 15 amp socket adaptor, or as required) and observe if the problem persists. If it does then at least you know that its not the desk or dimmer at fault.

 

I presume that this a mains supply and not a generator?

[Vanjast]

Had a look at that product link you gave.

It seems that this equipment has a 3 phase input, and you're mentioning 2 Single phases of 63A each.

If this is the case you'd have load balancing problems, and as mentioned, maybe the generator (if used) cannot handle this.

 

Also mentioned, is to check your connections/plugs. I find the easiest way to find a problem is to look for a hot (Hot temperature to the touch) plug. A connector/plug with a high temp is a bad connection and plays havoc with any connected electronic systems.

 

With the control desk.. the sliders get full of c.r.ap. A bit of Electronic contact cleaner (carefull which one you use here as some cleaners might be acidic and destroy the electronics) on the slider accompanied with gentle sliding of the slider helps get rid of any glitches - Check the master sliders here.

:up:

 

A concurrent post has been automatically merged from this point on.

 

Forgot this...

Does this problem appear immediately after switch-on or does it appear sometime later ?

 

If sometime later - I'd go for a power connection problem, related to temperature.

If immediate - I'd look at the desk sliders. Doesn't the dimmer pack have a manual test button or test mode, where you can isolate the DMX input ? This will 'finger' the dimmer if it's there!

 

Just thinking aloud..

[Kazeja]

Not being familiar with the dimmers, and as you mention that they pulse when set to zero, does anyone know if the DMX screen is isolated from earth in these racks.

 

1. Do the dimmers pulse with the DMX disconnected from the desk?

2. Do the dimmers pulse with the "other" DMX line disconnected from the desk?

3. Do the dimmers pulse without the fogger(s) in circuit?

4. Do the dimmers pulse with the DMX connected to the desk but the desk turned off?

5. As in 2 but desk disconnected/unplugged from the mains?

6. Has the mains fed to the desk got a good earth?

 

Standard practice is for the DMX signal to be earthed at source. Problems could be encountered if the desk has a missing earth.

Also, I assume screen from both sources of DMX will be tied together in the desk.

 

Hopefully if you can provide answers to the above we may be able to get a better picture of the source of the problem.

[jason.fallon]

Its Happening Everywhere I Go. Its happening with all of my frog desks when I plug them into the dimmer rack. Its not immediate, its fairly constant. The Haze makes it twice as noticeable.

 

In reply to kazeja,

 

1. Going to try this tomorrow. They dont pulse when the DMX is plugged out but Am going to try plugging out with the DMX hold feature on the dimmer

2. Yes

3. Yes

4. No

5. No

6. The frog is powered from an external power supply so this I will also check out tomorrow

 

I'm only ever running off mains power. There is a phase correction feature on the rack themselves. The manual is quite vague as to the exact function of this but Would this have any effect being on when the desk is being ran off only one phase?

 

Really appreciate the advice guys. I'm gonna try your suggestions when I get down early tomorrow

 

Thanks

 

Jason

[boatman]

It sounds to me very much like a faulty cable, especially as the effect gets worse when the fogger is connected. A few more questions:

 

1. Have you tried Ynot's suggestion (in post #2) of terminating the run?

 

2. What type of cable have you used for the DMX runs?

 

3. Do you always connect everything together with the same cables in the same sequence?

 

You haven't told us whether or not your runs are terminated, so that's the first thing to try. It that makes the effect worse it's almost certainly a faulty cable. With modern lead free solder (all hail RoHS) joints can appear to be good and work for audio but won't work for high speed digital signals like DMX. A useful tool for you is a DMX tester, which you can buy here for example. This can test cables with both 3-pin and 5-pin connectors for both analogue and digital continuity. For anyone with DMX problems it's worth its weight in gold.

[Roderick]

With all respect, to me this sounds like a power problem, most likely a floating neutral, rather than a DMX problem.

Does the fogger run of the same supply as the dimmers? The extra draw would explain the worsening of the flickering when it is plugged in.

 

I would have the 'phase correction feature' thoroughly checked by a licensed electrician.

[jason.fallon]

Right I attacked it a bit today and made some progress. I changed both dimmers to run off 3 phase which made no difference as regards the pulsing. What I did discover however was that the phase correction was off on one and on on the other and this was causing the random lights flickering, not however the intermitent dimming which was still happening. On this occasion I think the power in the hall may have been a factor but tomorrow its going on another gig so I can continue my pursuit then.

 

I haven't tried terminating the run but I might just try that. Its regular DMX cable. Not sure the impedance but its the shiny stuff.

 

The pulsing did stop when the DMX was pulled out. The dimming is so intermittent that I couldnt tell wherther it stopped or not when we pulled out DMX

 

Thanks

 

Jason

[jason.fallon]

Hi All.

 

Just wanted to share this incase anybody encounters similar. I discovered the problem recurring when I put the dimmers on the next gig. Turns out every time I turn off the dimmer, The phase correction feature on one of them resets itself to "no". Once I set it to yes its fine. I'm guessing its some form of internal battery dead.

 

Thanks for all the suggestions.

 

Jason