EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: uoficowboy on December 03, 2013, 09:28:55 pm
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I have a couple old pieces of HP test gear with stiff 10 turn pots. The pots work just fine - it's just the bushing/bearing/whatever that hold the shaft. I've verified this by taking the bushing/shaft assembly out completely and it was still really stiff. These are Bourns pots that are pretty easy to disassemble from the 70s. They look like the ones shown here: http://www.talonix.com/shop/item.aspx?itemid=12651#.Up5MqOLWKgk (http://www.talonix.com/shop/item.aspx?itemid=12651#.Up5MqOLWKgk)
I'd rather not replace the entire pot since they are original parts and are still otherwise working well. But I'd love to find a way to make them less stiff. Any ideas?
Thanks!
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Maybe little wd40 on the shaft?
Sometimes grease in pots hardens over time.
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What about putting the bearing on the electric drill and giving it a good run at highspeed?
Or maybe let it sit in oil/grease.
I've done the following with bike chain and DAMN it moves smooth after but have no idea if it will work for a bearing.
Heat up some snow white petroleum grease in a container on the stove until it's all melted and very runny.
Let the bearing sit in the liquid it for ~20min.
Stay next to the container and make sure it doesn't get too hot (smoking). You don't want a grease fire.
After 10-30min remove the bearing and turn off the heat.
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No wd40 too corrosive and could damage your pot. Also no contact spray.
I would disassemble and put in a little jar with IPA in a ultrasound cleaner till all is clean. Re assemble and add the correct fresh grease for the bearings
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He means the bearing by itself (he removed it)
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No wd40 too corrosive and could damage your pot. Also no contact spray.
I would disassemble and put in a little jar with IPA in a ultrasound cleaner till all is clean. Re assemble and add the correct fresh grease for the bearings
I don't know how to add grease to it though - it seems to be internal to the device.
I worry that cleaning will just make it worse and get rid of what grease is left.
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take a picture of the bearing next time you have it out. if we can see it, we can offer more advice on how to lube it.
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A bit of vaseline would probably work as replacement grease.
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Vaseline dissolves rubber, though, so be careful. Most oils dissolve rubber. Polar molecules vs. non-polar molecules, if I remember my high school chemistry.
There are places on the Internet better than this which can help you find the proper lubrication methods.
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Would have thought a good silicone based spray lube would work ok
Have used silicone on plastics, rubber and similar like neoprene with no issues
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Would have thought a good silicone based spray lube would work ok
Have used silicone on plastics, rubber and similar like neoprene with no issues
Have to be careful so none rubbed off onto the wiper or element otherwise it would insulate it.
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I think in the OP mentioned the shaft had been removed. Not sure if this means jts away from the contact area so should be ok if it is... Solong as any excess is wiped off
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Have to be careful so none rubbed off onto the wiper or element otherwise it would insulate it.
just googled a bit and found that there are lubricants for the wipers and "resistance"layer of potentiometers, didn't know that:
http://www.nyelubricants.com/lubenotes/Lubenote_Potentiometers.pdf (http://www.nyelubricants.com/lubenotes/Lubenote_Potentiometers.pdf)
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See attached for photos. I pulled this part and rotated it in my hand for a while. I also attempted to remove the teeny little E clip that is on the front of the shaft (just barely visible). But it was too small and too stiff - so I couldn't get it. I did notice after reinstalling it the pot is turning a bit better now. I wonder if just being tweaked for a while loosened it up... It still is a bit stiff but not as bad as one of my others.
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A drop of light napthetic oil on the shaft will help a lot. Often sold as vacuum pump oil, so you will probably buy a gallon can and have a lifetime supply ( or in my case a 3 month supply as I do use a lot of it) and it is a very good general purpose lubricant oil, a lot better than the spray can ones.