Pearl Problems

[peter]

I thought I'd post this, to see if anyone had had a similar problem.

 

We have a (several years old) first generation Pearl (wooden sides) which has a mysterious fault. Various problems seem to occur with the desk, including multiple patching of fixtures and various crashes. The desk was sent back to Avolites, who couldn't find a fault. The desk was behaving normally.

 

Then, last week, we had a problem with our Diamond 3. Sticky buttons, which led to the desk crashing.

 

At this time, someone put two and two together and came up with a plausable solution. Both the original generation Pearl and the Diamond 3 are running non-opto isolated DMX-outs. Due to the makeup of two-core + screen cable, you could analogise its construction to be similar to that of a capacitor. As such, a charge is building up in the DMX cable which is then released when certain buttons are depressed, or the DMX cable is removed. This release of potential causes a short circuit somewhere in the internals of the desk, leading to crashes or other malfunctions.

 

 

So, does this sound like a reasonable suggestion, or are we barking up the wrong tree? Avo confirmed that neither desk has opto-isolated outputs.

[gareth]

Never heard of that one before, but I suppose at a push it might be possible. Try sticking an opto buffer straight after the output on a very short (i.e. a few inches) piece of mux cable, and see if the problem goes away ...

[Brian]

It's worth pointing out that non-isolated DMX out is the preferred topology. Pin 1 should be ideally firmly strapped to the mains earth of the desk.

 

Other things to think about are external RF fields and general crud on the mains. Don't know if you can boorow one from IT but either a good mains filter or better yet a small on-line UPS might be worth trying.