Control/Dimming - Grand Master fader issue on Strand MX

[stevefox]

Last Thursday my school held it's first event requiring the tech group. I noticed this late last year, but didn't get the time to really look at it until now. When bringing the Grand Master fader on our Strand MX board up or down, the light's levels will jump around. For example, bringing the fader up from 0, the lights won't come on until 3 or 4, and then pop on, then between 5 and 10 will pretty much jump to any level and produce a flickering effect. It only does this with the Grand Master, and a smooth fade can be accomplished crossfading between the A and B set of faders.

Basically, I'm asking if this is something we can fix ourselves, or do we have to send it in or get a new board?

[Sony]

Originally Posted by stevefox

Last Thursday my school held it's first event requiring the tech group. I noticed this late last year, but didn't get the time to really look at it until now. When bringing the Grand Master fader on our Strand MX board up or down, the light's levels will jump around. For example, bringing the fader up from 0, the lights won't come on until 3 or 4, and then pop on, then between 5 and 10 will pretty much jump to any level and produce a flickering effect. It only does this with the Grand Master, and a smooth fade can be accomplished crossfading between the A and B set of faders.

Basically, I'm asking if this is something we can fix ourselves, or do we have to send it in or get a new board?

Sounds like it's almost definitely a bad fader pot to me. I would suggest sending it back to Strand or better yet replacing it completely if possible. It's not really something you can fix yourself because it is soldered onto the board.

[waynehoskins]

Sounds like a dirty pot to me. What I'd do:

First try blowing that pot out. It probably won't do anything, but sometimes you'd be surprised what that will do.

Failing that, I'd try cleaning the pot, if it were my board, with tuner cleaner -- but in your case, being a school console, I wouldn't. I would either consult the service manual or Strand tech support to see what procedure they recommend for cleaning a dirty pot on that console. I've heard rumors that certain types of cleaning solutions (tuner cleaner, Deoxit, Cramoline, etc.) can damage certain types of pots, so since it's not yours, I'd let the manufacturer tell me what to clean it with. Actually, I'll revise that. I'd let the manufacturer tell me what it shuold be cleaned with, then present that to whoever it needs to be presented to for approval (in case it breaks, you know), and proceed only if I get that okay -- it may well be a good occasion to get a new board.

If it's beyond cleaning (which is rare), if it were my board, I'd replace the pot. Or convince myself that I really didn't need the GM.

[FMEng]

I concur that using electronic cleaners not made specifically for faders and pots is not a good idea. That said, Caig makes a product intended for that use. I have not tried it, but I have had good luck with their other products.

I know the Strand MX very well. The grand master isn't terribly important on that console, so the safest course of action is to just avoid using it. If it gets to the point of being so flaky that it affects console operation without being touched, then I'd try the cleaning spray. If you wind up sending the console out for repair, having tried cleaning it yourself won't hurt anything.

As a last resort, I would carefully cut the circuit board trace to disconnect the fader wiper, then jumper the other side of the cut trace to the top leg of the fader resistance, using 24 guage solid wire. That would effectively remove the fader from the circuit. Keep in mind I don't have a schematic, so this is risky. If done carefully it can be reversed.

Whatever you choose to do, try it when you have a few weeks of down time to resolve it if it makes things worse. Don't do it the day before the big show.