[R-390] RF Deck, Module Washing (dishwasher)

[Bill Hawkins]

Very interesting.

I made powdered dishwasher detergent one time because all commercial 
products were perfumed. IIRC, it was equal parts of TSP and a powder
for chlorinating pools.

The book "Oscilloscopes" by Stan Griffiths contains a chapter on
washing Tektronix scopes that has worked well for me:

Take the scope outside. Remove tubes or they will have no markings.
Hose it down if you have soft water, else use bottled de-ionized
water. Do not immerse the scope in a tank. Do not spray an open
transformer (problems with HV arc tracks) if the water isn't really
deionized. Variations in results have been traced to the degree of
deionization. What works in one part of the country may not work
in another

Use an industrial detergent. In 1992, that meant Simple Green or
Breeze, but both have been reformulated for higher profit and
various environmental protection laws. Stan sprayed a liquid
detergent solution with a spray gun. I made a bucket of dilute Simple
Green and used a medium brush or a tooth brush. Sprayed SG from the
bottle on tough spots. Once you've done all that, go back and do it
again, rinsing off the dirty solution with clean solution. Stan set
his spray gun to 100 PSI and held the nozzle within a few inches of
the area to be cleaned for the second time.

Keep moving during the washing. Don't let the detergent dry. When
done washing, rinse it thoroughly. You are trying to remove anything
that might become conductive after you're done. When you are satisfied
with the rinse, use an air nozzle or cans of "air" to remove as much
water as you can. Turn the equipment over 90 degrees at a time and
blow the water out at each turn. Maybe one 180 degree turn is enough.

When no more drops of water come out, start drying. Stan recommends
a box heated by a light bulb to 120 to 130 degrees F. I used the warm
sun and low humidity of a Minneapolis late fall or early spring.
There's no such thing as too much drying, particularly if there are
crevices that the compressed air couldn't reach.

Note that a Tek scope of tube vintage was laid out with ceramic
terminal strips, so that most of the components were out in the open.
I wouldn't try to clean the underside of the IF module with a tooth
brush, but the 100 PSI spray gun might work.

And I would never clean electronic equipment in a dishwasher,
especially not with unknown stuff in the detergent and unknown 
ionization of the water supply (and unknown heat from the drying
cycle.

YMMV, as we ad-aware folks say.

Bill Hawkins