# Control/DimmingDimmer 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.

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?

##### 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.

##### 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!

##### Custom Title
Fight Leukemia
Used to work for the local power company, so probably way more cautious than most.
You never know who you're talking to online! Just wanted to put in the caveat

#### 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

#### Jay Ashworth

##### Well-Known Member
Wow; the Rt60 on this thread is *really* long...

#### Pyrotech

##### Member
Wow; the Rt60 on this thread is *really* long...
Or, loose nut behind the keyboard issues...

Not sure what the problem was when I was trying to quote.

Just trying to say I'm the same way when talking to folks about pyrotechnics.

#### Jay Ashworth

##### Well-Known Member
You do have to be careful about loose nuts:

Fight Leukemia

#### Jay Ashworth

##### Well-Known Member
For the record, we've heard *all* the punchlines to this on Facebook.

#### MNicolai

##### Well-Known 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.

#### JonCarter

Who built that piece of $%^&*? STEEL bolts on a bus bar electrical connection??? #### Dionysus ##### Well-Known Member Who built that piece of$%^&*? 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
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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