Solder Problems (PDP-8/m related)

From: Dwight Elvey <>
Date: Thu Dec 2 18:41:17 1999

Lawrence LeMay <> wrote:
> >
> > >This machine sounds as though it's full of bad connections, alas. Have
> > >you cleaned _all_ the edge fingers on all the boards? Have you cleaned
> > >(and tightened if necessary) the PSU connectors. Have you cleaned the
> > >backplane slots?
> >
> > I cleaned the edge fingers before even turning it on, though I think I'll
> > clean them again. I'll have to take a look at the PSU connectors. I blew
> > out the backplane slots with canned air, how can you do a better job of
> > cleaning them?
> I just vacuumed my backplane, but most of the gunk in my pdp8/e appears to
> be a result of deteriorating foam. I forgot, what was generally
> considered the best compound to use for cleaning pdp8/e edge connectors?
> I think it had 'gold' in its name...

 Here is what I do in all of my old machines ( note: some of these
have been operational for more than 20 years without a single
contact failure ). First I clean any gunk form the contacts
with a lintless swab and isopropyl alcohol. I then coat the
contact with a thin layer of silicone grease ( such as DC#4 ).
I insert the connector a couple of times and I'm done.
Do not use ordinary grease, it doesn't work. Don't use
heat sink grease either. The silicone grease
is also good for flaky switch contacts and IC sockets as well.
 I have heard all kinds of reasons why to not use my method.
The only one that I agree with is that once the grease is
on a part, you can't get stamped ink to stick to the surface.
This was a problem during original manufacture and doesn't
effect old stamps that were already there.
 I'm sure that I'll get the same bunch of flack that this is
a bad idea. My point is that it works. Short of replacing
the connectors, I've not found anything that works as well.
Received on Thu Dec 02 1999 - 18:41:17 GMT

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