PDP-8/a cleaning

jim stephens jwsmail at jwsss.com
Tue Apr 25 04:08:13 CDT 2017

On 4/25/2017 1:39 AM, Pete Turnbull via cctalk wrote:
> "Little residue" would be more accurate, and some of that residue will 
> be water (look up "azeotrope") - plus you need a lot of alcohol for 
> something the size of a PDP-8 backplane.  Blow dry, even after an 
> alcohol rinse.
In the process of cleaning optics indeed you need air and other means to 
do that, you are right.  But in this case I'm suggesting the alcohol as 
a way to displace water out of internal parts.  The spotting or such is 
not much to worry about in the cleaning job on a computer part.

But in optics the process is much longer and elaborate, but still needs 
the ventilation to be sure you don't have a problem with fumes.

We had a booboo in assembly that required cleaning and we no longer had 
freon cleaner we wanted to use in that quantity, so we went with the 
water / alcohol process.  A switch had defective sticky seals on it and 
they had all gotten waterlogged.  Vendor claimed they would survive 
water process wash and they were wrong.  Paid us quite a bit in credit 
for messing up a couple hundred boards before we caught the problem.

Solution was to rewash in water then alcohol rinse.

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