"Ross Herbert"
Adrian Jansen
:If its an audio control, and its 'crackly' that is a sign that its
:getting DC current through it. So its well worth checking any
:capacitors around the pot, and ensure they are not leaking DC current.
:Old electros are well known to do this. And after you replace the
:electros, you may still have to replace the pot to get rid of the noise.
Adrian, I note the "design engineer" tag on your post but you don't seem
to be
aware of why pots get "crackly".
** It's a very deep mystery to sooooo many out there .....
Inside a potentiometer there is a wiper which
makes contact with the resistive element and every time you move the wiper
it
attempts to dislodge some of the resistive material. The more oftern the
wiper
is moved the more material gets dislodged. It is these dislodged particles
of
resistive material which cause the noise in 99% of cases.
** The wiper mechanism would easily move tiny carbon particles out of the
way ( ie like a road grader) - if it were not for the fact that nearly
all pots and faders (ie slider pots) are packed with grease to improve the
mechanical " feel " when operated.
This grease has the bloody horrible habit of migrating onto the surface of
the resistive track AND moving metal parts over time - so mingling with
and compacting the carbon dust into a thin layer of *non conductive* gunk.
It is this **gunk** layer that must be removed to restore good operation
to a "noisy" pot.
Products like WD40 do it so damn fast and well, it makes your head spin.
It is NOT necessarily
(in fact, rarely ever) because they have DC flowing through them.
** True, not only because leaky electros are nowadays a rarity - but
that it is very rare now to see coupling electros subjected to any
significant DC voltage at all.
Dual +/- supplies have long been the norm in all ( non valve) audio gear
so there is simply no DC voltage to block.
..... Phil
