[Collins] Re: 75S-1

[Dr. Gerald N. Johnson, electrical engineer]

The odds are extremely high that if the paper capacitors in the radio
aren't Sprague glass sealed Vitamin Q, or haven't been replaced, they
are leaky. Its not worth the effort to check for leakage, just replace
all the capacitors. I like Sprague Orange drops, I've abused them and
they still don't leak after several decades. 

Resistors all through the radio have probably gone up in value. All
carbon composition resistors except the imitations (which were really
carbon film resistors in a molded case) made by IRC go up in value with
time, heat, and humidity. Its a random walk, not exactly linear. IRC
resistors (distinguished by the mold flash visible at the rounded ends
and down the sides of the molded package) were not allowed by the
Collins specification for carbon comp resistors.

Collins spinner knobs came after the S-1 era. And are prized because
there are more S-1 than loose spinner knobs.

I like to clean a dry radio with a 1/2" flat artists paint brush (an
ordinary one may work, just that MARS issued a box of artists paint
brushes one time to each member) to move the dust from the corners while
sucking it up with a small (maybe 1/4" inside diameter) nozzle on a shop
vac. I use a milker inflation for that small flexible nozzle, there are
computer cleaning kits more available these days with that small nozzle.
The relatively short bristles of the artist's paint brush are effective
at loosening dirt from the corners. And since the artist's brush is
thinner than the ordinary paint brush its more effective at getting into
corners an between components.

73, Jerry, K0CQ, Technical Advisor to the CRA
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.