Re: Super Serial trouble.

["Mark Cummings" <NOTfigjams@primus.com.au>]

> Another thing, this board was terribly dirty so I cleaned it with
> denatured alcohol (or is "white spirits" the correct English term? You
> know the stuff you aren't supposed to use for lighting charcoal for
> your barbecue, but most people do it anyway.)

One of the correct solutions used for circuit board cleaning is ISOPROPYL
ALCOHOL, we use it at work for exactly that purpose. This is 7% Alcohol by
vol, I don't know about the rest though, mostly water ? White Spirits leaves
a residue as far as I know. I have also seen some techs use Acetone, but I
would be very wary of that, as it can eat into the fibre glass resin.
Personally I have never tried Acetone for this purpose.

> After the cleaning, the cursor blinker 555 acted up (the cursor
> blinked about five times faster) so I had to replace it. From this I
> gather that this alcohol (which conains 6% of water) isn't the right
> stuff for cleaning boards.... what would you use?

6% sounds about right. the real trick is the technique and the drying. First
remove all the components that are socketed. Start a tap with warm running
water, clean the board first with lots of ISOPROPYL ALCOHOL with one brush
until its running reasonably clean with minimul flux (the brownish gunge
left on some boards). Then add plain dish washing liquid and a long soft
brissled brush, circling around all sockets etc. Add a little water to soap
it up. Rince under the warm water, continue with the brush until there is no
more detergent bubbles. Dry the board using compressed air, making sure to
get all traces off the board. Check the board for traces of soap/flux. Flux
appears as a kind of oil stain or snail trail. Soap tends to go white
especially around component legs. You normally have to repeat this process a
few times (2 or 3) before you get a sparkling new board. Then replace the
socketed components where they came from.

Another thing I have started doing after the above method is to spray all
the sockets with an electrical cleaner that doesn't leave any residue. This
ensures all the water is displaced from sockets etc. and cleans the contacts
prior to adding the chips.

This is how I was taught to clean boards, and I have used it successfully on
motherboards, interface cards etc. The only thing to avoid is getting water
in areas that can't be dried, like trim caps or pots or switches. These
should be de-soldered from the board first and put back later, then clean
around the new soldering as best as possible using cotton buds and alcohol.

Mark