Re: [CAD_CAM_EDM_DRO] Cleaning Circuit Boards

At 07:55 AM 11/26/00 -0000, you wrote:

>This is a little off topic, but my servo amps cards and cages are
>dusty and grungy from working ten years in a machine shop before they
>moved in with me. What's the best way to clean electronic stuff?

I have often cleaned all boards from old NC machines with a strong solution
of hot water and detergent. I don't soak the boards and I handle them very
carefully. I return each board to its origional slot because I don't know
what bad inputs or outputs were "fixed" by swapping them to slots that
didn't use them.

I brush them very gently with a soft bristled brush and rinse them in a
running stream of hot or warm water to remove the residue. Using an air
hose with a regulator turned down or a shop towl in multi thicknesses
fastened over the end is also a good Idea. Because many shop lines have
air and oil in them, the shop towel also works to clean the air.

The reason I use hot detergent is my uncertainty concerning the materials
of which the components are made. Any solvent stronger than hot water and
detergent will find something it can take apart that I don't want taken
apart.

Don't let the boards soak in the detergent. You are trying to get high
resistant shunt circuits cleaned off, not create new problems.

Drying the boards can be done in shop air if you do it the way I have
described, or in a warm oven. Don't bake the boards for the same reasons
given above. You are trying to keep the boards in the ordinary range of
their operation while you clean them.

Now for the real problem set - The Connectors.

After boards have been removed and replaced just a few times, the
connectors become unreliable. You can reset the spacing on elco and edge
connectors to factory specs. If you push them too close together to get
better contact, you will push them right out of the injection molded
connector blocks. Worse yet, you will break the components.

Connectors become erratic because plating wears out, You are getting well
under 50 millionths of gold on these connector faces and it's gone after a
few insertions. Ron Wickersham, another list member, suggested that I try
the solution used for low voltage audio connectors on such connectors. It
works great, but must be reapplied after each insertion and removal. So
you must try to troubleshoot to the board with minimum board swapping, a
good thing for the connectors anyway.

The other major sources of erratic behavior, besides marginal components,
include vibration and heating, each fixible through common sense.

Ted Robbins