Re: Upper limit of timing resistor value in a tropical setting

On Fri, 20 Sep 2024 14:18:26 +0530, Pimpom <Pimpom@invalid.invalid>
wrote:

Take a typical domestic environment in a tropical region, rather humid
at times. Assembled board is not conformal coated and some dust is
expected to seep into the box over the years and settle on the PCB. The
unit is low voltage and low power with just a few watts dissipated when
on, and left unpowered for days on end.
>
An R-C combination is used to set timing of around 1 sec. which is not
critical (long-term variation of up to 10% is tolerable). If it gets
very bad, the board can be cleaned but this should not be required as
regular maintenance.
>
Under these circumstances, what's the highest timing resistor value
you'd feel comfortable with?

Maybe 1 Kohm.  Others have said 10K and 100K.

But why not dip the board in hot wax, to seal the surface?  One can
repair the board without removing the wax, and just re-wax when done.

Back in the dead-bug era (late 1960s), we would put the vectorboard
with wired and ICs in a shallow tray of molten wax, and let it cool
and solidify, protecting the circuitry both physically and
electrically from damp and salty dust.  If repairs or upgrades are
needed, melt wax, pull board out, make changes, return to wax tray.

Joe Gwinn