Mark Zacharias wrote in message
.com...
"N_Cook" wrote in message
...
Mark Zacharias wrote in message
.com...
"N_Cook" wrote in message
...
Deeper than just saying clear out the grease. 2 in 2 days, first
input
selector of an amp , not explored in depth, second vol control of a
music
centre.

First had radial contacts that were slightly staggered and the fixed
contacts were in line , second was exact radial contacts and
staggered
fixed
contacts. On the second I took some R measurements before and after.
There are 3 contacts, one common and the other 2 staggered to pick up
CW
or
CCW rotation. Just measuring between the 2 sense contacts as at some
point
they are cross connected, measured 2.5R each of the posistions but
very
tiny
position to get this reading. Ladled out and then dissolved the
grease,
reassembled and took readings again . Now 1.5R each bridging
posistion
and
a lot easier to find that posistion, ie more latitude. I imagine from
the
consistency of the R readings that something to do with deforming or
block
under one of the contacts reducing the contact to a very small area
and
then
only marginal connection posistion bridging the 2 contacts. I assumed
the
electronic sensing was one line before the other but perhaps duration
of
both contacts on simulataneously, or not, is also something to do
with
normal sensing



Clean the moving contacts and stationary contact area as you would
relay
and
switch contacts. Better to replace the control, but this will fix it.

Mark Z.



I've never seen a relay with grease it it. Rotary encoders or the BCD
type
ones, it is the grease thats the problem but exactly why it is a problem
is
still not fathomed. I assume a hardening or accretion process that
eventually wedges under a wiper. Why do they not use "dry lubricant"
perhaps
locksmith's graphite as long as in a minute quantity.




The problem on rotary encoders is not so much the grease, although I
believe
that is a contributing factor.

Every encoder I've seen with this problem suffers from tarnished contacts.
It's obvious, and you can tell by a simple close inspection. Just like a
vcr
rotary mode switch. Clean with a fiberglass brush and De-Oxit. Repeat the
process. Turns tarnished metal clean and bright.

I still favor replacement when possible.

Mark Z.



I'm still going with a mechanical grease problem. If it was tarnish it would
have to be tarnish on a sprung contact as once erroneous it is near enough
the same problem on all spokes of the disc. The hardening grease is also in
the shaft area and puts up noticeable resistance to turning, the first
indication it is a grease problem. I first came across the grease problem on
sub min mixer pots that are more the size of presets. The wipers are made of
such fine metal it takes little compaction of the grease to get under them,
the resistive track is fine no wear at all .