[Collins] Help Request

[Dr. Gerald N. Johnson, electrical engineer]

I've no experience with the 651S-1A.

These are the techniques I'd apply.

If the cards are plugged into sockets, I'd clean the contacts with a
gold contact cleaner, such as Gold Guard.

If there are cables I'd clean the connections with fractions of a drop
of DeOxit on each one.

If the boards are bolted to the chassis, I'd tighten each mounting
screw, perhaps after adding a shake-proof lock washer to each to improve
the grounding.

Then if needed, I'd try alternating heat and cooling first on major
sections of the radio to see if I could induce the failure and cure.
Then I'd narrow down my heat and cooling (hot air gun or hair dryer and
a spray like Freeze-mist, canned refrigerant). Often that technique can
narrow an intermittent to the component. First I'd resolder that
component. If that didn't fix the intermittent, I'd replace that
component. If an IC, I'd cut the leads from the body and pull the from
the board one at a time, then clean up the solder holes with solder wick
and install the new component.

In summary, I'd suspect connectors, whether board edge or cable, then
board ground, then individual components. Switches and dial encoders are
equally suspect and may need a quarter drop of DeoxiT per contact to
clean them up.

73, Jerry, K0CQ
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.