Cleaning circuits

From: Hans Franke <>
Date: Mon Jul 27 08:45:25 1998

> A few questions about clean(ing) circuits:
> a)Can dust cause any damage to a PCB? Can it short anything?

Yes and No - no direct harm is done, but dust turns out
to be a good insulator, so the core temerature of the
chips rise if they are covered by dust - even a small
dust film can be difficult. Higher core temperature means
higer stress, more aging and sooner irreversible failure.

> b)What do you recommend for cleaning out PCBs if there's lot of it,
> or spiderwebs, mold whatever?

Yes cleaning is a must. I use several methods:

1. If the board is small enough to fit, I use an ultrasound
   cleaning device. This method is not usable if stickers
   or other non wter resistant markings ar on the board
   (and should be keeprd intact). ultrasound cleaning removes
   anything in less than a minute.
2. If the board is to big i use oridinary water (but destiled
   is prefered to avoide calcium (?) stains). Maybe with a
   little soap in front.
3. If there are some stickers to preserve, I use only short
   'splashes' of water, from a mouth washing device.

Alle three methods requiere intensive drying. So I first
use a soft (frotee) towel, and then wave the board to dry
of thebigger parts. If the board is very crowded (like a
IBM-PC or XT) I will use a centrifuge (spin dryer). The
board has to be fixed to get the right. Also a hair drywer
for blowing _cold_ air is usefull to drive out the water.
I never use warm air, since it is less efektive and leaves
more stains on the surface. But as I said, using destiled
water makes it less cruical when it comes to drying.

Also 'canned' compessed air as available in some shops can
be used to drivew out the water from deep corners.

You don't have to remoe all chips.

4) Now if I can't use water, I thake several soft towels
   (fabric) and rub off the dirt. A sponge with a liite
   soap water, and a second one with clear destilled water.
   Also a stick an linnen is usefull to remove dirt from
   the edges.

The ultrasound method can be used for a lot of parts.
Even sonme keyboards do well - Original PC-Keyboards
could be dumped without any preperation into the water
and cleaned in just a few seconds.


> c)Does distilled water cause rust?

Basicly almost no, but after touching thesurface it
isn't destilled water :) The main reason for rust
is high humidity always dry your precesious little
ones and store them not in an swamp like climate
(sorry if you live in FL or somewhere near the

> d)Can distilled water be used to clean circuits?

Yes - see above.

> e)As I understand, tap/spring/rain/etc. water is full of minerals
> and that's why it's conductive as well as rust-causing

Yes/no - If you dry them, they won't pick up rust.

> f)A while ago, I picked up a bunch of 5.25" diskettes, which I hardly
> allowed to dry before I put them into the plastic box. Now I
> looked inside, and mold is spreading from the Microsoft Assembler
> diskettes onto the Apple II ones. What is safe to use to clean
> the mold (it's reeely disgusting!)?

Thats the problem with Microsoft - They always want to
pollute the environment - and as we see not only the
Internet or Java, even simple helpless Apple Disks are
to be transformed in non standard monsters :)

Normaly I could suggest just to dump them since most of
the software is not very unique. But again here are
several levels of restauration:

1. If you only want to keep the software:

Rip of the cover, clean the disk with cold air and / or
alcohol (no nor brandy - use isopropyl alcohol) - take
a _clean_new_ linnen and pour alcohol on. now go soft (!)
ofer the disk to remove any parts - try to 'roll' the
fabric to change the surface and lift of the mold.
now place the disk into a new cover (always open only
one side). If the disk wasn't damages itself you now
should be able to read the content and duplicate it.
I used this Method several times in data recovering

2. I you just want to keep the cover (special print, or
just since it is an genuine early Microsoft :):

Take a sponge with warm destiled soap water and sponge
it down (Never look at the disk ... it's a shame :).
Drying and now storing a at a dry place to prevent the
mold to come up again - Mold doesn't like dry places to

3. You want keep both:

Combine one and two - so you have a funktional copy
and a displayable disk. Or just use method 1 and transfer
the label to the _new_ copy.

4. You realy want to keep this disk (worst case):

Forgett it - at least You have to do it like in 1) but
you'll have to open the original cover _very_ carfully
clean the disk, clean the cover AND replace all this
fabric fleece inside the disk for new fabric - thats
_very_ sifficult - and even if you mange this, the
disk well always look damaged. The possibility of
reinstaling mold is also the highest.

Some tips:

- Never use Mold covered Disks - or if you have to,
restrict the usage to on 'mold-only' drive.

- Don't use disks lying next to moled disks - the little
friend is already there.

- Store your disks always dry and with enough air
circulation.closed cases can be deadly to your

- Avoide high humidity

- Avoide low humidity, since the fleece will become

- Avoide heat - Some disks could start to loss their
data as soon as 60 degree (140F)

- Avoide cold - Never use disks below 10 degree (50F)
the stress results in higher aging (remember, flopy
disk drives are still cutting tools like a turning lathe)
Also the magnetic film will loose the tightening if the
temperature is to low (same as when to high (>80 degree 180F)

I already dumped several hundered Disks I recovered
previously from basements and garages because of


Ich denke, also bin ich, also gut
Received on Mon Jul 27 1998 - 08:45:25 BST

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