On an old piece of crt based UT equipment (none-o-scope) that I have to fix
occasionally, had a sealed rotary switch that gets flashy to the point
where the instrument in non-usable, They are soldered to a front panel PCB
and then through the panel, along with about ten other controls and of
course short and fragile wiring harnesses. It is a huge amount of work to
get that PCB off, plus if you do, the switch it sealed and made of
unobtainium. Luckily, the switch that goes very flashy and makes the
instrument non-usable is on the outside edge of the PCB. My Solution?
Please don't cringe too much. I use an exacto and slowly and carefully
scrap and carve away at a small section of the plastic switch housing until
I have a small hole in it. I spray the contact cleaner in it and rotate
the switch. It then works perfect and the instrument is usable again.
On Mon, Apr 15, 2019 at 9:57 PM Dennis Tillman W7PF <dennis@...>
wrote:
For years I've struggled with what to do about noisy pots. Until now the
best solution I have come up with is to remove the knob and drip contact
cleaner down the shaft. It only works a small percentage of the time. And
I'm not sure it can even work on ganged pots at all. Plus it is quite messy
since it is almost impossible to control the burst of contact cleaner that
comes out.
Faced with the same problem once again an idea struck me while I was
staring
at the back side of one of the very common black square pots (single or
ganged). The ones I'm referring to have four tiny screws holding them
together from back to front.
SOLUTION: Remove one of the screws and squirt the contact cleaner into the
hole. All four of the screws screw into a metal plate at the front of the
pot. So the screw hole passes through every section of the pot (or multiple
pots regardless of how many there are.
It's too early yet to tell how effective this is. I only just discovered
it.
Dennis Tillman W7PF
