Dimmer Module: Bright flash?

[Charc]

Edit:

Well, I decided to give Strand Tech Support a try, and Patrick was helpful and informative.

It just looks like I have another bum module!

[Dustincoc]

The only time I've ever heard a snapping sound come from a dimmer is when its being overdrawn due to a short and blows the SRC module.

[mnfreelancer]

Does the dimmer still work? Have you disconnected the new wiring, reset it etc? What kind of dimmer? Did the blue smoke sneak out?

[Charc]

Strand CD80sv rack. Don't have time to pull the module out now. No smoke or anything else.

[David Ashton]

A not infrequent problem is the snubber capacitor across the output, it can blow with much smoke and effects and then the dimmer carries on happilly.Strand used to fit a .1 mf across the input to the control transformer on each dimmer, similar effect.Not one of the harder problems to detect.

[Charc]

Got a maintenance guy to come help me troubleshoot it for an hour after school. The conclusion, after reading continuity between hot and ground off the ol' DMM, from the raceway, is a dead-short, somewhere between the raceway and the module...

[JD]

But not in the module? Hummm... The three big ones are usually in the module:
1) Shorted snubber,
2) Loss of isolation between SCR and frame,
3) Loss of isolation between choke windings and frame.
Outside of that, most "flash" problems resulting in a short have to do with foreign objects (Screws, hardware) finding there way to the wrong spot.

I am assuming you made that reading with the load removed as a cold load will often read as close to a short.

[Charc]

Originally Posted by JD

But not in the module? Hummm... The three big ones are usually in the module:
1) Shorted snubber,
2) Loss of isolation between SCR and frame,
3) Loss of isolation between choke windings and frame.
Outside of that, most "flash" problems resulting in a short have to do with foreign objects (Screws, hardware) finding there way to the wrong spot.
I am assuming you made that reading with the load removed as a cold load will often read as close to a short.

We swapped the modules, and had the same issue, so determined it was not an issue with the module.

That reading was made with a module in place, but the breakers tripped.

[JD]

Originally Posted by charcoaldabs

We swapped the modules, and had the same issue, so determined it was not an issue with the module.
That reading was made with a module in place, but the breakers tripped.

Very strange. Backplane issues are rare unless some object fell in there. Since it is a fixed location install, you would not usually expect hardware to be coming loose. Tell us what the find!

[Charc]

Originally Posted by JD

Very strange. Backplane issues are rare unless some object fell in there. Since it is a fixed location install, you would not usually expect hardware to be coming loose. Tell us what the find!

The find is to not use that slot/circuit.