Exploring rotary encoder problems
N_Cook
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
Mark Zacharias
news:j5c6e0$34i$1...@dont-email.me...
switch contacts. Better to replace the control, but this will fix it.
Mark Z.
N_Cook
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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.
Michael A. Terrell
N_Cook wrote:
>
> Why do they not use "dry lubricant" perhaps
> locksmith's graphite as long as in a minute quantity.
The grease is needed to prevent metal migration across the open areas
as they slide. I've seen people try to run similar items dry, or with
other crappy lubricants. Graphite would need something to hold it to
the board, and you would need enough that would cause leakage as the
sliding contact compacted it to the surface. Good old fashioned 'GC
Tunerlube' does an excellent job on sliding contacts.
--
You can't have a sense of humor, if you have no sense.
N_Cook
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I can see that with multifunction DVM rotary dials where there is small gaps
between tracks. But the 2 rotary encoders I looked into this week were about
1mm wide spokes tracks with the contacts at the periphery so spaces of about
5mm of insulator disc material
Michael A. Terrell
Not 'between tracks', but between the pads a moving contact uses. 25
years ago I serviced CATV converters for a living. I had to use a soft
eraser to remove the tracking between contacts if the original lube had
hardened, or where an outside service company had wiped away the old
grease and used a fiberglass brush in a half assed attempt to clear away
the smear of silver. I did well over 1000 repairs in four years with a
return rate of a little over .2%. Over 50% of the units returned from
the outside service company were either bad, out of the box or failed
within a month. I was hired to create the in house service department
because we had over 1/3 of our converters either at the outside company,
or on a UPS truck and in transit. We added 350 new customers without
buying any new equipment, after I had the in house repair facility set
up. We went from the worst rated CATV company in the reigion to the
top, in under six months.
Michael A. Terrell
N_Cook
What was the spacing between pads on those CATV units? The pads or tacks in
these switches were about 5mm. As far as I can tell the problem was not
metalisation smear over the insulated gaps but a problem while in pad
contact. No visible smearing of metalisation seen on either switch. These
pads are just like spokes of a wheel and once the problem started it is much
the same around the whole disc, not specific to one or two positions
Mark Zacharias
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.
Michael A. Terrell
N_Cook wrote:
>
> Michael A. Terrell wrote:
> >
> > Not 'between tracks', but between the pads a moving contact uses. 25
> > years ago I serviced CATV converters for a living. I had to use a soft
> > eraser to remove the tracking between contacts if the original lube had
> > hardened, or where an outside service company had wiped away the old
> > grease and used a fiberglass brush in a half assed attempt to clear away
> > the smear of silver. I did well over 1000 repairs in four years with a
> > return rate of a little over .2%. Over 50% of the units returned from
> > the outside service company were either bad, out of the box or failed
> > within a month. I was hired to create the in house service department
> > because we had over 1/3 of our converters either at the outside company,
> > or on a UPS truck and in transit. We added 350 new customers without
> > buying any new equipment, after I had the in house repair facility set
> > up. We went from the worst rated CATV company in the reigion to the
> > top, in under six months.
>
> these switches were about 5mm. As far as I can tell the problem was not
> metalisation smear over the insulated gaps but a problem while in pad
> contact. No visible smearing of metalisation seen on either switch. These
> pads are just like spokes of a wheel and once the problem started it is much
They were about half the width of the moving contact. You didn't have
to be able to see the silver tracking before it would detune a dozen
channels. the board was phenolic, instead of fiberglass, and the
switches weren't meant to be cleaned. I may still have a couple of the
boards form the switches, but it's been 25+ years since I serviced that
equipment.
Michael A. Terrell
serviced. I had to repalce every switch that had been cleaned with one.
A soft ink eraser removed the tracking without scratching up the board.
The later replacements came with notches cut into the board to prevent
tracking.
N_Cook
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 .