Potentiometer Problems on EVS Vicmarc Lathe

[Kidbee]

Having problems of fluctuating speeds on my Vicmarc. Phoned the company and they said to spray the potentiometer with an electrical contact cleaner. I followed their instructions and the problem went away but has returned within a couple of days.
I was also going to take the steel plate door off below the lathe that has the digital read-out and blow that section out with compressed air, but cannot get two of the screws with the 3mm allen key heads, undone. Nor have I touched the white electrical box at the back of the lathe yet.

The lathe is a 2009 model and has not had lots of use. However, I am lead to believe that problems with potentiometers are not uncommon.

I have not approached Vicmarc for a price on a new potentiometer yet.

Hoping someone may be able to tell me how they solved the problem. Replacing the potentiometer at home does not appear to be difficult as it has three wires that need to be soldered and I have an electric soldering unit that can do that.

[Cliff Rogers]

Mine has gone that way too.

I haven't attacked it yet but when I do, I make sure it is disconnected from the power & use some contact cleaner lubricant in the holes on the back of the pot & turn it up & down several times to clean & lubricate it.

Keen to see how you get on.

[Jim Carroll]

A replacement pot is not expensive and an easy to change.

The wires are soldered on so just need to be unsoldered and then soldered onto the new pot.

I am unsure of the longevity of spraying contact cleaner

[BobL]

I'd say the pot has got some very fine dust inside it and while contact cleaner can wash it off the contacts temporarily, eventually id dries out and makes a nuisance of itself again and no amount of contact cleaner will get rid of it.
Opening it up to clean it out is probably not worth the hassle so replacement makes sense.
If you do that it would be worth opening up the old one to see what it is like and posting some pics here.

[Cliff Rogers]

There is contact cleaner & then there is contact cleaner with lubricant, the 2nd on is the one to use with a pot.

[Kidbee]

There is contact cleaner & then there is contact cleaner with lubricant, the 2nd on is the one to use with a pot.

After doing some internet searching I realise that is the case. The electrical contact spray was bought at Supercheap Auto. Yesterday I went to Jaycar and bought some Deoxit which I am yet to apply. It may have cost more than a new potentiometer but the second reason I bought it is that my iPhone charging port is acting up and I hope it may correct that problem as well.

http://www.jaycar.com.au/Service-Aids/Chemical-Aids/Other-Chemical-Aids/DeoxIT-Contact-Cleaner-%26-Rejuvenator---Solution-Kit/p/NS1436

If that fails I will replace the potentiometer as suggested. And yes Bob I will pull the old one apart and post some photos.

[Kidbee]

UPDATE. I sprayed the pot on two separate occasions with Electrical Contact Spray and for awhile the problem of the fluctuating speed went away but returned. I then brushed the pot with the cleaner I bought from Jaycar and for awhile the problem went away again but also returned.

The next thing I did was to blow the pot out with compressed air, using a borrowed compressor from my son, which removed water-like droplets which may have been the spray residue etc that did not evaporate.

Since then I have had no further problems and now a happy chappy.

The photos below show (1) Potentiometer (2) Inside of electrical box (3) Speedcontrol knob that has the potentiometer on the other side of the wall. SORRY BUT THE PHOTOS DUPLICATED!

354947354946354945354947354946354945



Vicmarc said "You can get a pot from jacar if you like. You can use any pot that’s around 20 -25mm. We use 5K wire wound 24mm."

....and the Deoxit fixed my iPhone charging problems by cleaning the charging port.

[markdem]

I would just replace the pot with something like this..

http://au.rs-online.com/web/p/potentiometers/7904209P/

Been IP67 rated, you will not have any issues with dust ingress. Just make sure the shaft size is right.
If fact I am a little surprised Vicmark did not use something like that in the first place.

Have fun.

[BobL]

UPDATE. I sprayed the pot on two separate occasions with Electrical Contact Spray and for awhile the problem of the fluctuating speed went away but returned. I then brushed the pot with the cleaner I bought from Jaycar and for awhile the problem went away again but also returned.

The next thing I did was to blow the pot out with compressed air, using a borrowed compressor from my son, which removed water-like droplets which may have been the spray residue etc that did not evaporate.

I doubt it was the water to begin with. If there was any water there it probably came from the cold contact cleaner propellant which cooled the pot and condensed some water. I'd say it was dust which started the problem.

[TimberNut]

I just had the same issue with my Vicmarc VL300EVS. Everytime I adjusted the speed, whilst rotating the potentiometer, the lathe would cut out, and then back in, getting up to the new speed eventually, but every time I touched the speed dial, it'd temporarily cut out.
I had replaced the potentiometer in 2008 (Vicmarc sold me one for $26 incl postage in 2008 - they saw me as a sucker I think).

I stumbled on this post, and thought that I might try cleaning the potentiometer this time, or sourcing it elsewhere. Jaycar have exactly the same spec one for $2.95. I decided to pull the back off my one, and clean it out, and when I did I noticed one of the armatures in it was bent in slightly. Based on how it's made, internally, I can see how this will happen again, over time.

There was very little dust in it, so the problem for me was a bent armature inside the potentiometer. It was simple to bend back with a pair of long nose pliers. If I have the same problem in the future, I'll just repeat this, or buy a new one from Jaycar.

At less than $3 to replace (and free to repair in my case), I can't believe I put up with the problem for as long as I did!

Disassembling the pot was easy, as there are very few moving parts, so if you are struggling with similar issues don't be afraid to try this. It was easy, and didn't even require me un-soldering the pot. I did it all whilst still wired up (but unplugged of course).


I'm posting this in case someone else has similar issues in the future.