Residue on K110 PCB

[BussoV6]

I was cleaning my new acquisition, a Monterey K110, and when I opened the case and looked at the back I saw (and smelled) this.



Does anyone know what the heck this white, stinky stuff is (that's what she said)? And can it be cleaned off?

[Muirium]

Mold maybe? Something nasty. Should be able to clean it off though, PCB's are fairly tough.

I see your K110 has the same kind of hairy handwiring up at the top of the PCB as mine! What a strange run of boards.

[BussoV6]

Yeah, the RJ11 jack wires!

Can I just use rubbing alcohol and cotton swabs to clean off the residue? Whatever it is, it doesn't appear to affect operation. The keyboard worked fine when I tested it.

[Muirium]

Sure. I've cleaned them with dish water as well. Just be gentle and don't use anything corrosive. Oh, and don't submerge the whole thing, obviously. Wiping is better.

[webwit]

^ Has been washing his b... oh well let's not go there.

[seebart]

What did it smell like?

[Muirium]

Depends on the deodorant… exercise usually alters their mood a bit too. Why you asking?

[XMIT]

That looks like mold to me. Use isopropyl alcohol and distilled water, and watch out for capacitors. Read on below...

High purity isopropyl alcohol (aka isopropanol, IPA) and (if you can find it) distilled and/or deionized water are the way to go for electronic cleaning. Do put these into a little squirt bottle for a thorough cleaning, such as:

squirtware.jpg (7.53 KiB) Viewed 2370 times

IPA is a mild organic solvent that won't do much against solder mask (green/blue/purple/red covering). It will penetrate into a raw (tan) fiberglass PCB some but it will evaporate. It does a great job of dissolving, for example, curry, or musty smells.

Do *not* use tap, well, etc. water. With those you run the risk of chlorine doing damage, and with calcium chloride and other dissolved minerals staying behind. Around here distilled water is 1 USD/gallon and often found in the baby food aisle at the grocery store. 91% IPA is about 2.50 USD/quart or liter and with the bandages.

Try to use lint free cloths for cleaning. A microfiber cloth, a sponge, and KimWipes are a better option than paper towels or cotton swabs.

Apart from moisture sensors (I've never seen one on a keyboard) the only water sensitive components are electrolytic capacitors. You risk washing away the electrolyte which is a Bad Thing when you power on the board. These are the components that usually fail first on most consumer electronics. They look like this, with either one lead at each end, or two on one end:

electrolytic-capacitor.jpg (24.08 KiB) Viewed 2370 times

Transistors, diodes, ceramic resistors and capacitors, ICs, and most other components are extremely well sealed.

Your best bet is to desolder the capacitors, give the board a bath, and replace them. Ideally use new replacements if you have them with the same ratings.

Hope this helps (maybe a nice review if you already know much of this).

[BussoV6]

I cleaned the back of the PCB today with some 91% isopropyl alcohol and an old car detailing microfiber cloth. Whatever that crap was, it came off easily and now the board doesn't reek of rancid solder flux and mold. Sorry I did not get any after photos! Anyways, when I first got this keyboard I suspected I was not the first one to open it as one of the screw slots was stripped a little. I think these two repairs confirm that. The small green wire I circled in red in the PCB photo, the resistor is below the IC.

[BussoV6]

I've given the K110 a more thorough test run. All the keys work, but some of them feel very sticky, certainly much more so than the Montereys on my Chicony KB-5181. Judging by the light brown color of the residue I cleaned off of the PCB, I'd say someone spilled coffee on it. Is there any way to clean or lubricate Monterey switches? What little research I have done says they are very difficult to disassemble.