Cleaning pots - what went wrong?

I had a slight problem with my joystick in that moving it to the right and holding it there caused the wheels on GPL to fluctuate slightly so I thought this could be a problem with one of the pots. So, after reading up on how to clean the pots in a joystick, I popped down my local electronics store and picked up some 'switch cleaning lubricant - cleans and lubricates switches, contacts and relays.' Well, after doing the business on my pots and leaving it for the required amount of time I plugged my joystick back in ready for some improved racing. Unfortunately the problem was still there, so I thought well maybe after a few laps things may improve. However they got progressively worse and after a couple of laps the wheels were flailing about so erratically that it was impossible to drive at all. :-( I just tried it again 24 hours later and the problem's still there, so what have I done wrong? Any advice will be greatly appreciated. -- Peter Ives

Well, In my opinion, as and electronic parts professional, your cleaning action washed away resistance track particles which had come deteched from the surface, but were still providing contact with the runner. I.e. the pot might have been dirty, but it needed replacing anyway. If I may make a suggestion: if practical (i.e. if it fits), replace the pot with a single turn sealed Cermet resistance layer type. Bourns has them, but the part number escapes me at the moment... Jan. ------ >I had a slight problem with my joystick in that moving it to the right ><snip>

Cheers for the info Jan. I've not heard of Bourns, but my local Maplins here in the Uk does Cermet typ pots. I've just checked in their catalogue. Problem is they come in various values, which I assume has something to do with resistance. Any idea which one's most suitable from this lot:- 47 Ohms, 100 Ohms, 470 Ohms, 1k, 4k7, 10k, 47k, 100k, 1M Thanks in advance! -- Peter Ives

Correct, gameports were originally designed to work with 100K pots. Make sure you use Linear Taper ones Peter!! Jan. ------ >100K is typical for most PC game controllers, but Thrustmaster uses >200K in some of their models. In any event, 100K will work fine. I've >replaced TM 200K pots with 100K cermets and had excellent results. >Trips ><Snip>

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>Correct, gameports were originally designed to work with 100K pots. Make >sure you use Linear Taper ones Peter!! >Jan. >------ >>100K is typical for most PC game controllers, but Thrustmaster uses >>200K in some of their models. In any event, 100K will work fine. I've >>replaced TM 200K pots with 100K cermets and had excellent results. >>Trips >><Snip>

Cheers for that! I had better get a new pot quickly as my trusty standby logic 3 joystick appears to be going the same way, although this one doesn't use pots, just those slider tracks. It's also showing the exact same syptoms. Must be all those right handers in GPL causing it. :-( How about coming up with some circuits that go anti-clockwise for a change. ;-) -- Peter Ives

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>>Correct, gameports were originally designed to work with 100K pots. Make >>sure you use Linear Taper ones Peter!! >>Jan. >>------ >>>100K is typical for most PC game controllers, but Thrustmaster uses >>>200K in some of their models. In any event, 100K will work fine. I've >>>replaced TM 200K pots with 100K cermets and had excellent results. >>>Trips >>><Snip>

Well, unfortunately Maplins here in the UK didn't have anything suitable in stock, so I took the troublesome pot completely apart and cleaned the tracks with some plain cotton wool. Certainly some of the carbon, since I had sprayed the pot, seemed to have been smeared all over the place. However, after cleaning the excess off and putting it back together, the joystick is working reasonably well. Not perfect, but better than before I sprayed it. One thing I noticed when I went to Maplins was that it may be difficult to get hold of an exact match of pot, especially the Cermet type. Does anyone here in the UK know of someone who supplies this sort of thing? -- Peter Ives

Get out your ruler and measure it up .. then go search for the pot at: www.digikey.com. I dont think they'll have a problem shipping it overseas to the UK. I've gotten some great stuff from them and they have just about every shape and size pot you could imagine. Matt

I believe 100K is standard for joystick pots. > >Well, > >In my opinion, as and electronic parts professional, your cleaning action > >washed away resistance track particles which had come deteched from the > >surface, but were still providing contact with the runner. I.e. the pot > >might have been dirty, but it needed replacing anyway. > >If I may make a suggestion: if practical (i.e. if it fits), replace the pot > >with a single turn sealed Cermet resistance layer type. Bourns has them, but > >the part number escapes me at the moment... > >Jan. > Cheers for the info Jan. I've not heard of Bourns, but my local Maplins

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> here in the Uk does Cermet typ pots. I've just checked in their > catalogue. Problem is they come in various values, which I assume has > something to do with resistance. Any idea which one's most suitable > from this lot:- > 47 Ohms, 100 Ohms, 470 Ohms, 1k, 4k7, 10k, 47k, 100k, 1M > Thanks in advance! > -- > Peter Ives

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Sometimes when cleaning a pot the cleaner will actually create resistence when it makes a sludge out of the residue from the carbon contacts. In this case, if you can open the pot and wipe it clean with a paper towel and put it back together you problems will be solved. % I had a slight problem with my joystick in that moving it to the right % and holding it there caused the wheels on GPL to fluctuate slightly so I % thought this could be a problem with one of the pots. So, after reading % up on how to clean the pots in a joystick, I popped down my local % electronics store and picked up some 'switch cleaning lubricant - cleans % and lubricates switches, contacts and relays.' Well, after doing the % business on my pots and leaving it for the required amount of time I % plugged my joystick back in ready for some improved racing. % Unfortunately the problem was still there, so I thought well maybe after % a few laps things may improve. However they got progressively worse and % after a couple of laps the wheels were flailing about so erratically % that it was impossible to drive at all. :-( % I just tried it again 24 hours later and the problem's still there, so % what have I done wrong? Any advice will be greatly appreciated. % -- % Peter Ives -- **************************** Michael E. Carver ************************* Upside out, or inside down...False alarm the only game in town. =-=-=-=-=-=-=-=-=-=-=-=-=-=-=<[ /./. [- < ]>=-=-=-=-=-=-=-=-=-=-=-=-=-=

>Sometimes when cleaning a pot the cleaner will actually create >resistence when it makes a sludge out of the residue from the carbon >contacts. In this case, if you can open the pot and wipe it clean with >a paper towel and put it back together you problems will be solved. Yeah, I did this a few days ago and, as you say, the carbon had smeared all over the place. Now I've cleaned it it's almost as good as new. I think I'll do this from now on at regular intervals, until I can get decent cermet pots that is. ;-) -- Peter Ives