Control/Dimming Dimmer Pack repair

Pyrotech

Member
While working on our first show (community theater) back from COVID, I found one of our dimmer packs was not working - address display flickered, but only partial segments. I swapped it with a spare, so the show went fine, but when starting cleanup and organization of the tech spaces post show, I pulled the cover to see if there were any visible issues before tossing it.

It's a Chauvet DMX-4 (photo of front attached). The row of pins above the small IC & row of resistors (other photo) is the back of the display. There is some white residue on the board that appears to be bridging some of the PC board traces.

1) Could this be the problem?

2) If so, is if possible to clean this with alcohol or some other non-destructive solvent and get the pack functional again? I'm a volunteer, so labor cost isn't an issue.

Or, given the ~$175 or so cost of a new pack, just go ahead and toss it and buy a new one?

Thanks
 

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Crisp image

Well-Known Member
You could try an electrical contact cleaner which is a really good product that evaporates quickly and see if that works. If so then all is good but if not the $175 to replace is not a huge cost.
Regards
Geoff
 

Jay Ashworth

Well-Known Member
Well, a bunch of your resistors are installed backwards, but that's probably not the problem.

<smirk>

All seriousness aside, that looks like the back of an IC, and that could indeed be conductive enough, whatever it is, to cause a problem. I would try isopropyl, yeah, with a stiff brush, and see if it comes up. If not, perhaps flux remover, if they still make that. :-} Or DeOxit D5, which cleans everything.

Do those units get stored in a hot place?

I don't *see* any popped electrolytics, but maybe there's one out of frame?
 

Mac Hosehead

Well-Known Member
Yes, the residue looks like some rosin flux that was left over. I don't think it is the problem but you could remove it with flux solvent.

I think the problem is more likely to be oxidation on the pins of the microprocessor IC in the socket. If possible without damage, you could remove it from the socket and then reseat it.

The choke in the picture looks discolored as if maybe it overheated with too much current.
 

Dionysus

Well-Known Member
Given the symptoms, SOMETHING is not happy, and without the knowledge and tools to diagnose and repair/replace the issue I'd say it's e-waste. Sending that to most repair places would cost more than replacing it.
As mentioned you can do what is within your means and give it a shot, and that can be worthwhile.
 

StradivariusBone

Custom Title
Fight Leukemia
I think the usual failure with these things is the triac going, but I don't think that is what you're dealing with here. I've seen the seven segment displays get weird on those shoeboxes before and I'd assume something was wrong on the low voltage side of things. Could be the micropro, could be the voltage regulator feeding it, unless something was spilled on the box I wouldn't think any of the residue is a culprit either.

Hard to diagnose with just a picture. Could be a good project to learn on, but be aware you are dealing with lethal voltage in there before you go in.
 

Pyrotech

Member
Do those units get stored in a hot place?
Not really. Room temp, the tech area upstairs gets extra warm, but probably never over 80F or so.
but be aware you are dealing with lethal voltage in there before you go in.
Yeah, thanks. Used to work for the local power company, so probably way more cautious than most. I'll give those traces a good clean and if that doesn't do it, assume it's a bad component and replace it.

Thanks everyone!
 

Pyrotech

Member
You never know who you're talking to online! Just wanted to put in the caveat :)
You never know who you're talking to online! Just wanted to put in the caveat :)
You never know who you're talking to online! Just wanted to put in the caveat :)
You never know who you're talking to online! Just wanted to put in the caveat :)
You never know who you're talking to online! Just wanted to put in the caveat :)
 

MNicolai

Well-Known Member
Premium Member
Fight Leukemia
The choke in the picture looks discolored as if maybe it overheated with too much current.

I'm no electronics engineer but that choke looks wasted as if all the insulating enamel on the windings has melted down like Chernobyl. This pack is likely beyond repair and ready for retirement to the great magic smoke party in the sky.
 

Dionysus

Well-Known Member
Who built that piece of $%^&*? STEEL bolts on a bus bar electrical connection???
Oh, that Chesnut has been circulating on facebook and other places for like nearly a decade. Don't remember where it originated, but you can be sure there were a number of electrical issues there if something like this was there.
 

MNicolai

Well-Known Member
Premium Member
Fight Leukemia
@Dionysus, yeah, I vaguely recall it was from an undeveloped country, but that could just be a broad assumption. Seems like many of the worst electrical/code violation photos come from other parts of the world where that kind of stuff is par for the course.
 

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