Control/Dimming ETC D20 Dimmer Failure

[DavidNorth]

Certainly in a case where there are a high number of power cube failures, we want to hear about it. We can talk about use, failure modes, facility equipment, HVAC, and the potential influence of nature [lightning] on a site.

Indeed we get a bad run of cubes from time to time and we can generally sort that out fairly quickly.

In order to be the best resource possible to you on this issue, please give us a ring and we'll hash out an answer and plan.

Thanks,

David

800-775-4382

 

[JD]

Be aware that if you have a large number of mods to fix, you can probably negotiate a deal with whoever you hire to service them. Back in the service biz, it was a dream come true when we would have such a customer because we could turn the shop into a production line and blow through the repairs in very short order. So, if you get the "Flat rate price = $$", SHOP AROUND!

 

[dramatech]

I seem to be the "Go to guy" in our community for fixing dimmer racks. I service two colleges and one community theatre that all have sensor racks, and two high schools and my own theatre that have EDI mark VII racks. Of these several dimmer racks, I have only had to replace SSRs on one of the EDI racks and one of the Sensor racks.
The EDI rack, is from my own theatre and in every case I can trace the failure to blown lamps. On the Sensor rack, which is a single rack, and has had about 8 failures in less than a year, I am pretty sure that the theatre has either one or several cables that have an intermittent short. This theatre is also the least maintained, and seem to ignore any advise I give them about checking their cables and instruments.

I also have made quite a few repairs of "shoebox dimmers" for the various facilities. When I replace a triac in one of the shoebox dimmers, I always take the new one to a 20 or 24 amp triac.
All of the failures on the shoebox dimmers can be traced to blown lamps or more commonly shorted cables. The shoebox dimmers tend to be used for practicals, where it is not uncommon to use "Zipcord" or Christmas tree lights.
When a lamp blows and part of the filament or support wires short against each other, the current draw, although only briefly, is too fast for the fuse or breaker, and too high for the solid state device, be that SCRs, SSR,s or Triacs.
I see the replacement parts as expendables, just like gel or gaff tape. It's just part of doing theatre business.

Tom Johnson

 

[MNicolai]

Thanks for the LOTO note; I had just turned off the breakers on the module before pulling them.

This is not necessarily an effective way of preventing harm to yourself. The circuit breakers deenergize the components inside the module, but once the module is removed, the buss bars at the rear of the rack are exposed and remain fully energized, capable of driving far more than 20amps of current through your body.

What is particularly dangerous is the risk of an arc flash in the rack, blowing you backwards and igniting you and your clothes on fire. The risks are low -- for years it was a fairly common practice to perform hot swaps and some people still do it, but the dangers are incredibly high for anyone unlucky enough to experience an arc flash in a dimmer rack.

If you must perform work on your dimmer rack, power down the disconnect or circuit breaker feeding it. When done with your maintenance, do a once over to your rack before you restore power to it such that you confirm that you have not left any tools in it.

A misplaced screwdriver left in the rack can cause quite the spectacle when you power the rack back up.

 

[JohnManderbach]

I came across this thread recently while looking for new information. I have 16 year old Sensor Dimmers and in spite of Mr. Terry's posts the SSR cubes fail, several a season. This does not pose a real problem because our dimmers are heavily used and yearly maintenance is in the budget. I will add that the Sensor dimmers are great. We recently upgraded to the Sensor+ CEM's and we are very happy with the technology.

But with that said, they almost always fail by flickering. Does anyone else have this experience? Is there a way to test the cubes to determine failure absolutely before throwing them away? Can I use this method? What is the control voltage needed to fire it? http://www.crydom.com/en/Tech/Tips/How to test an AC solid satate relay.pdf

Any help is appreciated. TIA.

 

[DavidNorth]

Is there a way to test the cubes to determine failure absolutely before throwing them away? Can I use this method? What is the control voltage needed to fire it? http://www.crydom.com/en/Tech/Tips/How to test an AC solid satate relay.pdf

Any help is appreciated. TIA.

Yes, you can use that method to test cubes, but I have a couple of safety suggestions based on experience. Place a fuse or breaker on the AC line feeding the load side of the power cube. The last thing you want is a short to burn the wire in half, pop the power cube and smoke your eyebrows. Also, place a small current [below 0.5A] fuse on the DC control side. If you have a power cube that is shorted from the line side back to the control side [very rare] you don't want the AC power to pop the 9V battery and ruin your dress shirt. One last hint, cover all the exposed AC terminals with a nice piece of Lexan to protect the cat [and yourself] when she walks over your project table when the power is on.

Only very damaged cubes have a short from the DC control side to the AC power side. ETC/LMI L86, Colortran, Teatronics, Strand and EDI cubes from the the late 80s and early 90s are sometimes prone to this but it has only happened in Sensor cubes due to lightning strikes, hence the rarity. A simple continuity test from the control side to the output side prior to connecting to the circuit can sort this out in most cases.

You may or may not find a D20 flickering issue with this test setup. The flickering is due to an internal component issue quite often created by long exposure to excessive heat somewhere in its use over the years. Feel free to PM me or call me to discuss further if you wish so we can exchange more info.

David