Cleaning 60's Boards From Old Heavy Dust

[sarakisof]

Hello everyone, after having electronically restored the insides of some lovely old vintage organs and antique radios in the past, i was always trying to fix and clean other things on outside/appearance as much as possible depending on their condition. So after dealing and replacing/creating broken plastic parts (even with 3D printer), switches, buttons, leather case parts etc.
i was wondering how those dark brown pcb board surfaces could be cleaned properly and effectively without damaging any of their sensitive components like paper resistors, caps, coils and so. Have tried some common contact cleaners without oil or pure isopropyl but did the job only in large surface areas. But i talk about -almost- total cleaning like by pressure spraying and rinsing the whole pcb.

Here you can see the heavy hard dust been there with ages and some only (plain) areas managed to get cleaned.





And here some pics i found from a site proving that they can be  totally cleaned.





White arrows show some small dust still next to those connector pads, proving that "there was heavy dust before", for someone who maybe thinks "dude, those boards were in pretty good condition before"   

Any input welcome.

[anotherjim]

Ultrasonic cleaner?...
https://ultrasonic-cleaners.org/how-to-clean-pcb-effectively-with-ultrasonic-cleaners.html

[sarakisof]

Nice but seems a bit expensive. I was thinking of a spray or something i could apply by pressure and rinsing.
Thanks though.

[mozz]

I'd be using 409 cleaner. Ultrasonic you would have to submerge the board, for a certain amount of time anyway, i wouldn't do that. I can tell the Farfisa boards. I actually had one but was so far gone and butchered, i have parted it out. Those sft352 are also used in the original Elka dizzy tone pedals.

[Axldeziak]

I've cleaned old computer motherboards in the dishwasher.
I also cleaned out a car's body computer board with a waterhose once I got it out of the car. Hornets had built a nest in the box. That was real fun to deal with.
That said, more modern commercial boards are coated to prevent oxidation and moisture contact. Old ones most likely are not.

[Ice-9]

I've cleaned old computer motherboards in the dishwasher.
I also cleaned out a car's body computer board with a waterhose once I got it out of the car. Hornets had built a nest in the box. That was real fun to deal with.
That said, more modern commercial boards are coated to prevent oxidation and moisture contact. Old ones most likely are not.

Are you having a laugh ?

[thetragichero]

following. i pickup organs to scrap for parts useful for guitar (amps,effects, etc) so i know how FILTHY they can get. 've got a 56 Hammond L112 that looks like it's full of that stuff from a gerbil cage - possibly why the owner said it "sounds like a jet engine" when turned on and i was able to haul away for free

[Axldeziak]

Are you having a laugh ?

No, it can be done. I've done it.
Look up the term conformal coating.

[sarakisof]

He is right i have been told many stories too from old repair men pushing away dirt from boards by using water pressure in the garden 
But i would like to avoid that hehe.

[deadastronaut]

air?....

i buy cans of compressed air which comes in handy for things like this ...with use of my wifes blusher brush.

cleans up nice. non destructive. 

[anotherjim]

Well I know there are restorers who remove the boards to clean, despite the number of wire connection to unsolder. I suppose they may as well since any electrolytic caps will also be replaced. An ultrasonic bath is a luxury, but its the best way to clean SMD boards that may have been contaminated and causing partial short circuits under the components and between IC pins.
Most old electronics will have a lovely sludge covering consisting of flux residue, wax and dust. To clean it in situ, you don't want to cross-contaminate, especially in an old organ that relies on open spring contact keying. So a soft brushing towards a vacuum cleaner nozzle is the first thing to do. If what is left annoys you, use a stiff artists brush. Try to avoid a liquid cleaner since it will only leave mud in places you can't remove it from. Clean open contacts directly with a contact cleaner, not by general spraying.
Dry air and brushing can generate static electricity. Be aware that early MOS and A series CMOS 4000 logic IC's had no built-in anti-static protection - so it's a good idea to keep the instrument plugged in, but switched off, so its metalwork is grounded by the wall socket.

[bluebunny]

i buy cans of compressed air which comes in handy for things like this ...with use of my wifes blusher brush.

Good idea, but I would have suggested a cheap paint brush.  More wife-friendly, i.e. your wife won't whack you with a saucepan!   

[amptramp]

Boards of this vintage usually have a lot of flux residue and possibly a wax buildup from paper capacitors.  To get rid of a lot of the wax, I use a straight flat-blade screwdriver.  After that, contact cleaner is usually necessary.  There is a huge variation in contact cleaner formulations and you have to be careful what you choose.  Cleaners containing hexane are flammable and they destroy rubber parts.  Cleaners with chlorinated hydrocarbons or chlorinated carbon will destroy styrene and various other plastics.  You may have to use one of the toothbrush-type hard bristle brushes.  If you heat the flux to soldering temperature, isopropanol can be used to remove flux but its effectiveness diminishes with the age of the flux deposit.

[PRR]

Yes, a domestic dishwasher IS a reference cleaning step in PCB fabrication. It may not be a preferred or allowed step, or it may be that a commercial dishwasher is needed, but it is A Thing in PCB cleaning.

It didn't used to be, and I'm not sure l like it on paper-base PCB.

Drying can be critical. And some dishwashers are pretty brutal dryers (HOT).

My first instinct on your boards is paintbrush and then a powerful air compressor with a sized-down blow nozzle. The ordinary home-shop (1HP) compressor won't keep up with a default mechanic's blow-nozzle except in short bursts. I plug the hole with wood and drill it small. 1/16"??

But grime-tainted dust won't come off with mere blowing.

That level of dust probably does no electronic harm. Any Meg resistors on there? I can understand you like it cleaner, especially (a-choo-choo) if you have to work on them

[deadastronaut]

i buy cans of compressed air which comes in handy for things like this ...with use of my wifes blusher brush.

Good idea, but I would have suggested a cheap paint brush.  More wife-friendly, i.e. your wife won't whack you with a saucepan!   

i get whacked regardless...

[stallik]

i get whacked regardless...

Whatever you're into Rob 

[vigilante397]

Is this something you're planning to do regularly? If so an ultrasonic cleaner is a worthwhile investment, and there are plenty out there under $100. The tech at the shop I used to work at had an $80 ultrasonic cleaner he let me use for boards a couple times, and it did great. They absolutely need to be properly dried before they're fired up again, but that's the way to go.

[sarakisof]

.Is this something you're planning to do regularly?

not really, it is mostly for this Farfisa boards. Own many other old stuff but this is the most painful to clean. On the other side from the old organs i own and have replaced so far those oscillator boards were the best in terms of functionality, meaning didnt needed to change any other component (except for all electros which i change for all organs in any cases). Look at those yellowish/rusted germaniums. Didnt changed any and my lady sings well! In other organs, more new aged and way cleaner guts, needed to replace many components to come back in business.

. The tech at the shop I used to work at had an $80 ultrasonic cleaner he let me use for boards a couple times, and it did great. They absolutely need to be properly dried before they're fired up again, but that's the way to go.

seems good and thanks for tip, but could i use an ultrasonic for a board with those sensitive tuning coils of an organ?

.But grime-tainted dust won't come off with mere blowing.
That level of dust probably does no electronic harm. Any Meg resistors on there? I can understand you like it cleaner, especially (a-choo-choo) if you have to work on them

you got my situation exactly here. Yeap it is that grime taint dust you cannot get rid of easily. And yeap i did tried with all kind of nethods, compressed air from auto shop,
brushes, even stiff hard cosmetic ones, you must push really hard with a lil watered q-tip to manage to see the "new-factory" surface of the board. But you cannot deal with all surface areas with a q-tip (always carefully with really little amount of water on the q-tip, just a drop) as you can understand, under some resistors, between legs etc. i fid managed to reach a good level though it was excausting, thats why started this thread.
By the way using 99.9 isopropyl instead of water didnt do the job right, it just moves the dirt around. This thing needs bath!!

Actually its a case like that, but i wouldnt dare to do so
Took me a week to carefully get rid of outter rust of tube amp chassis and transfos. Didnt wanted to pull out all layout components from inside and rust off chassis completelly (that would be ideal though) as all of them from back inside were perfect like new.
Huh, in the sake of this, i remembered smthng else i had back in my mind:
Is there any proper way to remove rust from outer edge of steel laminations? I m sfraid to do anything on as i am afraid i could destroy adhesive there 

https://youtu.be/7Rv6OfgcPpw

So bottom line: if ultrasonic wouldnt hurt smthng sensitive on an organ board like this, i guess this is the winner. Any secure though of anyone experienced in organs would be kindly appreciated.

[PRR]

> way to remove rust from outer edge of steel laminations? I m sfraid to do anything on as i am afraid i could destroy adhesive there

The old-iron Mojo is in the rust. (??)

There's no adhesive. There IS some kind of insulation between the laminations. (Old stuff used shellac; these days it is carefully applied Oxide, micro-thin "rust".) You don't want to destroy that and get electric conductivity between laminations. Although a few nicks do no harm, shoving it against a power wire-brush until it shines (and all the edges smeared together) is probably not a good thing.

Light brushing with a brass brush should be fine. Work "with the grain", not across the layers.

_I_ would follow with a wood stain, oil-based, "black". This will absorb into rust and pits and harden in a few days, seals the surface against dry storage. (If you put it back in the damp chicken-shed another couple decades, the rust is going to come back no matter what.)

[sarakisof]

Thanks for the tips, i read and learned many things while waiting for a response here, from complete restoration tube amp (trafo pulled out) to removing rust and "sealing" a P/T.
Read that trafos don't really like ultrasonic cleaners (as expected) so i think putting those boards with tunning coils wouldnt be a good idea too.
Anyway by reading all these i felt more comfortable and free of fear about using smthng liquid even for couple of secs. on electro's, mkts, paper resistors, styrene caps and so, i will try to find (if lucky) some spare boards of dead organs and experiment with.

About tube amp, i am thinking of give whole chassis included circuit underneath , except for trafo, a bath into an ultrasonic when find time. I have a friend whos dentist so i think can help.
I have no idea about liquid (distilled+green soap isopropyl?), temp and time of process used though.

About trafo, i am planning to soft type toothbrush "with the grain", but i read that it is better to avoid any kind of oil, like using silicone grease or other things that contain oil. I guess it is not a "don't" but it doesnt fixes situation for ever (if we could say that in terms of rust), as PRR mentioned it will be back after decades.
So i am planning to just seal it up using a metal varnish.
Read about a product named Fertan or smthng Rust Converter liquid (not remover) because it can react with rust more deeply inside and convert it.
Silicone grease, wood stain, metal varnish, 2-3 layers, Fertan?