LD90 fault

[Mr Steve]

Hello,

 

I have a Strand LD90 which is misbehaving. It's connected to a basic Strand 100 series DMX desk. When you bring the faders on the desk up off 0% the corresponding dimmer channel (lantern) will flicker. If you use the control panel on the LD90 to bring the lanterns up, they fade normally. The desk has been swapped for another 100 series from another studio space and the fault remains. Could there be some sort of fault with the DMX input stage of the LD90 - is this a common issue, or I should say *was* this a common issue, as I know these racks are pretty old. Any ideas?

[patrick_keys]

Do you have any DMX devices downstream of the LD90, and are they working properly? Is your line terminated?

[vinntec]

Perhaps before you look into Patrick's suggestion, take the desk up to the dimmer room and plug it straight in with a single cable and ideally disconnect anything else coming out of the dimmer (and replace with a terminator). If the dimmer now responds correctly, you immediately know that the dimmer's DMX circuits are working fine and there is something between the control room and the dimmer which is causing the problem.

[DrV]

The input stage is about as bog standard as you can get but is reasonably well protected. I would check the wiring first, as suggested above, but if it needs any work on the processor drop me a pm.

Dave

 

P.S. worth trying to jury rig a simple, short DMX line direct from a desk to the LD90 to eliminate any outside influences.

 

Perhaps before you look into Patrick's suggestion, take the desk up to the dimmer room and plug it straight in with a single cable and ideally disconnect anything else coming out of the dimmer (and replace with a terminator). If the dimmer now responds correctly, you immediately know that the dimmer's DMX circuits are working fine and there is something between the control room and the dimmer which is causing the problem.

 

Ha ha - Snap!

[Mr Steve]

Seems to be some cable fault. There is a loop-through box in an upstairs gallery - plugging in here directly works, then going back downstairs then also worked.

 

Thought I'd query the input as this is a super basic desk > panel > dimmer set up and the cable was not visibly damaged; not even dry joints. Anyway, solved.

[sandall]

I'm chucking out some old manuals, including one for LD90, so if it is any use drop me a PM

[Tomo]

XLRs are a wipe-clean contact.

The act of unplugging and replugging will remove crud and some corrosion, so can indeed fix a connection if it's been left connected and untouched for years.

 

However, a more likely explanation is that it's borderline somewhere, and you're just a bit luckier now than earlier.

 

Check that the line is terminated - measure the resistance between D+ and D- from where the console plugs in. It should be around 120 Ohms.

If it is not terminated, then go fit one and see what happens.

 

A broken wire in the DMX chain can easily cause this, and a terminator will find the problem.