Alcohol bath question

[mao91]

I've used 99% isopropyl alcohol to clean motheboards, GPUs, etc. without problem. This one is a bit different. I repair audio equipment and a customer has a large console mixer with an LED meter not working properly. Since it's an Allen & Heath, each channel strip has its own dedicated card. One of the cards was replaced by a previous owner, but it's not functioning properly. Upon inspection, my best guess is there is some sort of contaminant on the card shorting out the signal path for the metering. Normally this wouldn't be a problem, but it's the signal path for the Right main channel LED and VU meters. Aside from the metering not working properly (both the VU and the LED are about 20dB too low on the meter), the actual sound output level and quality is unaffected. 

So, my proposed solution was to take it out and give it an alcohol bath. However, there are two faders soldered onto the board, along with the LED meter. I know the board will be unaffected by the alcohol bath, but I'm unsure about the meter and faders. Does anyone have any idea how the alcohol may interact with those? I know it's not explicitly computer related, but... just curious. 

[BobVonBob]

It probably wouldn't be the best idea. Some types of plastic are damaged or clouded by isopropyl alcohol, and I would guess the VU meter uses plastic on the front. Same story with the materials used as bumpers in faders (usually o-rings). Try some electronics contact cleaner, or just be very careful not to get the isopropyl alcohol on the front of the VU meter or in the fader.

[Emanbaird]

How important is it? i wouldn't drench it in even 99% alcohol.

If this is a high cost repair, i would probably just re-solder most of the board,

 

If it's more of a favor thing i would probably just  ask him if he wants you to try it

[mao91]

6 minutes ago, Emanbaird said:

How important is it? i wouldn't drench it in even 99% alcohol.

If this is a high cost repair, i would probably just re-solder most of the board,

 

If it's more of a favor thing i would probably just  ask him if he wants you to try it

Well it's a card itself, not the whole board, fortunately. 

Unfortunately, we've been having trouble tracking down a replacement card. This one contains signal path for a bus, matrix, and main send. The ones that are just regular channel strips are running close to $300 for replacements. I'm guessing this one might cost more, IF we can find it. So we're hoping to repair the one that's here. If nothing else, he said he's fine using the board as is and just using an external meter for the main L/R, but if we can fix it, obviously we'd like to.

[Emanbaird]

Yeah, based off what i see, i wouldn't bring alcohol anywhere near that lol, it would most definitely ruin the card if used in excess 

[mao91]

1 minute ago, Emanbaird said:

Yeah, based off what i see, i wouldn't bring alcohol anywhere near that lol, it would most definitely ruin the card if used in excess 

I wish I had gotten more pictures of the card in question. This mixer is actually an hour and a half away from where I am, but next time I go I'll take pictures of what I think may be causing the issue as well. We're obviously just trying to figure out exactly what's going on before we go about the tedious process of removing the card.

[Emanbaird]

it looks pretty fragile, i can't tell whether it's analogue or digital, but if it's analogue you may be there for a while

[mao91]

11 minutes ago, Emanbaird said:

it looks pretty fragile, i can't tell whether it's analogue or digital, but if it's analogue you may be there for a while

It is most definitely analog, which is exactly why we want to diagnose first, take apart later.