Exploring rotary encoder problems

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.

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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 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.

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You can't have a sense of humor, if you have no sense.

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

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.

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You can't have a sense of humor, if you have no sense.

That should have read, "I did well over 10,000 repairs in four years, with a return rate of a little over .2%."

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You can't have a sense of humor, if you have no sense.

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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

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.

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.

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You can't have a sense of humor, if you have no sense.

Fiberglass brushes did more damage than good on the equipment I 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.

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You can't have a sense of humor, if you have no sense.

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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 .