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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 6th Nov 2017, 5:40 pm   #1
idlerbiker
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Default Cleaning and repairing a Corroded computer board

Hi guys,

Have any of you succeeded in cleaning and repairing a corroded/rusty computer board with some chip being static sensitive.

I don't mean battery corrosion, just water..

I read on one website that you can use just soap and warm water, another just distilled water and another just use a dishwasher!

Some just remove all components and clean the board and some just say leave the components on!

I just want a sensible method so can any of you suggest one?

Paul
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Old 6th Nov 2017, 6:11 pm   #2
kellys_eye
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Default Re: Cleaning and repairing a Corroded computer board

You need to identify the corrosion to properly treat it but I've had good success cleaning boards using IPA.
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Old 6th Nov 2017, 6:50 pm   #3
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Default Re: Cleaning and repairing a Corroded computer board

As I've posted on the Forum previously, I tend to try citric acid solutions on stuff like this. Remember that this is sort of "lemon juice" in terms of its acidity but it is an excellent chelating agent, so really good at dissolving metal corrosion products. You can buy the powder cheaply in Wilko. Lots of info on Google.

Soaps can be caustic, can contain salt. Salt (chloride) is damn hard to remove (at trace levels) once it's on metal, so tends to re-start corrosion.

B
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Old 6th Nov 2017, 9:54 pm   #4
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Default Re: Cleaning and repairing a Corroded computer board

Hi.
When I used to work for a company servicing arcade machines I think they used an ultrasonic cleaning bath. I know when I was cleaning by hand that on one board the ic sockets had got corroded, so had to be replaced. I think IPA was good for cleaning, but if there were any deposits left on the board then clean water and a small amount of washing up liquid is what I used. but you do need to carefully dry the board ( not too much heat ! ).
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Old 6th Nov 2017, 10:36 pm   #5
SiriusHardware
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Default Re: Cleaning and repairing a Corroded computer board

One of the problems with liquid corrosion is that it tends to turn solder into something else entirely, something which will just refuse to melt at the touch of a soldering iron. So you find an IC with half the legs dissolved off it and then try to desolder the remains of the legs from the PCB and clear the holes, and that's often when the fun really starts.

The other problem is that like rust on a car, once it gets going, it keeps going. Even if you identify several tracks and through-holes which have rotted away and repair them, a few months / a couple of years later the rot will often be found to have spread further and caused even more damage.

At work we generally declare PCBs with more than the slightest amount of fluid ingress damaged beyond repair. In some cases we could make them work, but we wouldn't be able to guarantee they would keep working, not with the time we generally have available to work on them.
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Old 7th Nov 2017, 12:07 am   #6
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Default Re: Cleaning and repairing a Corroded computer board

There are a range of different solutions depending on the nature of the problem. What exactly are you trying to do?
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Old 7th Nov 2017, 1:11 am   #7
Bazz4CQJ
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Default Re: Cleaning and repairing a Corroded computer board

Quote:
Originally Posted by SiriusHardware View Post
One of the problems with liquid corrosion is that it tends to turn solder into something else entirely, .
Gee, I thought alchemy had passed in to history . As he did say 'water', I think we can be less dramatic. And one of the real reasons why car rust never ends is that once chloride is in something it is so damn hard to get it off. Read about the recovery of the early 'Holland' class submarine; took 6 years of high-tech washing to get rid of the chloride.

B
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Last edited by Bazz4CQJ; 7th Nov 2017 at 1:34 am. Reason: spelling
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Old 7th Nov 2017, 2:10 am   #8
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Default Re: Cleaning and repairing a Corroded computer board

Was your board powered when it got wet?
I was once asked to look at a camera that had got wet.
The guy told me he had dried it as soon as possible.
It turned out that he had just dried it on the outside with a towel.
It had been dropped into the dirty sea water in the hull of a boat.
As the battery was still in it all the tracks were dissolved off by the electrolytic effect.
There was no chance of fixing it as there was still water in it after it had been carried back from a sunny beach in some hot country to UK.
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Old 7th Nov 2017, 8:59 am   #9
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Default Re: Cleaning and repairing a Corroded computer board

I routinely wash arcade machine PCBs whole. They are often filthy and have been badly stored, sometimes in damp conditions. Hot water with washing up liquid it and a decent scrub trying to avoid damaging any labels does the job. Then it needs a very thorough rinse, then drying promptly in a warm place with the board vertical, turning it round from time to time to allow any water trapped under components to escape and evaporate.

Don't worry about removing components unless there are PCB tracks under them that might need repair. The chances of damaging any of them by static discharge are slim, since water with detergent in it is pretty conductive.

Chris
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Old 7th Nov 2017, 9:13 am   #10
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Default Re: Cleaning and repairing a Corroded computer board

When in the TV trade I often got a particular Bush set which had had coffee spilled into the back. I took the offending board and carefully washed it using detergent, rinsing very well afterward and drying thoroughly over a few days. I then found I had to replace all the coils, but after this it was as good as new. Usually always the same board. I had this occur at least three times while I was working there and it worked every time.

Obviously this happened soon after the original accident.
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Old 7th Nov 2017, 9:14 pm   #11
SiriusHardware
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Default Re: Cleaning and repairing a Corroded computer board

Quote:
Originally Posted by Bazz4CQJ
Gee, I thought alchemy had passed in to history . As he did say 'water', I think we can be less dramatic.
Water is normally the source of the problem I described, solder turning into something with the consistency of grey granite which WILL NOT MELT no matter how hard you try.

We get a lot of PCBs back which have been used in supposedly watertight cabinets in outdoor locations. Sometimes, the cabinets aren't assembled as 'watertightly' as we would like.
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Old 8th Nov 2017, 1:03 am   #12
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Default Re: Cleaning and repairing a Corroded computer board

Quote:
Water is normally the source of the problem I described, solder turning into something with the consistency of grey granite which WILL NOT MELT no matter how hard you try.

We get a lot of PCBs back which have been used in supposedly watertight cabinets in outdoor locations. Sometimes, the cabinets aren't assembled as 'watertightly' as we would like.
Well, as per the Mag Loop thread, it does seem that some expensive bits of kit which are intended to operate outside still fail due the effects of atmospheric moisture.

B
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Old 8th Nov 2017, 8:34 am   #13
Craig Sawyers
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Default Re: Cleaning and repairing a Corroded computer board

I've washed all sorts of boards from my Tektronix gear in the sink. Warm soapy water and a soft brush to get into all the crevices. Rinse under hot tap. Shake out as much water as possible and put in the airing cupboard for a day or two.

In fact Tektronix used to wash the entire scope in their service centre before trying to fix or calibrate an instrument. Attached.

Craig
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Old 8th Nov 2017, 4:53 pm   #14
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Default Re: Cleaning and repairing a Corroded computer board

Aren't new pcbs washed with water after soldering, anyhow these days?
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Old 8th Nov 2017, 5:49 pm   #15
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Default Re: Cleaning and repairing a Corroded computer board

That's true, and the soldering flux is specifically chosen to be water-soluble.

Chris
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Old 8th Nov 2017, 6:40 pm   #16
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Default Re: Cleaning and repairing a Corroded computer board

A few comments. Pure water wouldn't cause corrosion. The problem is it's very rare to find pure water. Generally it will be at a minimum rainwater which is not pure.

Then there's the problem of surface contaminants on the PCB possibly even from manufacture so even if you do add pure water its no longer pure. Not all fluxes are washable or require washing, some are what is known as self cleaning. In theory the soldering process renders them inert but that's not always the case. There is a specific kind of test known as ROSE that measures the equivalent value of NaCl in micrograms per square centimetre. Different types of application drive different cleanliness requirements.

Using PCBs in cars means we get to know a lot about this kind of problem because they are very humid places. Temperature changes combined with that humidity can cause significant condensation, and many items are permanently powered these days so you have a nice power supply to allow dendrites to grow and tracks to dissolve.

Of course if some muppet in the factory decides to use some random other flux they found and a paintbrush, you can be stuffed.
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Old 9th Nov 2017, 8:01 pm   #17
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Default Re: Cleaning and repairing a Corroded computer board

ok guys.. here it is..
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Old 9th Nov 2017, 8:13 pm   #18
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Default Re: Cleaning and repairing a Corroded computer board

Looks like a Commodore PET PCB.
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Old 9th Nov 2017, 8:29 pm   #19
cmjones01
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Default Re: Cleaning and repairing a Corroded computer board

That'll be fine. It's the same era of technology as my arcade PCBs. Kitchen sink, hot water, washing-up liquid and a soft paintbrush, then a good rinse and dry.

I'd be more careful with the keyboard. Keep that dry because the keyswitches won't like water, and any liquid will tend to carry dirt into the keyswitches (don't ask me how I know...) Blowing with an air duster is probably the best bet.

Chris
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Old 11th Nov 2017, 11:51 am   #20
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Default Re: Cleaning and repairing a Corroded computer board

This reminds me again of the BBC method for getting coffee out of a Neve channel strip - flush down the loo asap, and sit on the radiator (the board, that is)
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