Inside a wirewound pot
in [Design]
|
From: oparr on 15 Jul 2010 22:07 Started a new thread since the other was getting long/convoluted/ confusing. Even though wiping back and forth cured the wiper bounce problem discussed in previous thread, I decided to pull the pot apart to see what exactly caused the problem. The design of this particular pot is such that there are no discrete steps as some had suggested. The helical element wire size and wiper carrier mechanisms result in the wipers tracking the element precisely. See this shot; http://www.pbase.com/eldata/image/126557137 Also, it's pretty obvious that this is not a "1-turn element" with some internal planetary gear mechanism faking a 3-turn pot (as one silly fellow adamantly suggested). More shots here; http://www.pbase.com/eldata/d300_wwpot Think I'll do the following; 1. Clean all parts with mineral spirits to remove any dried lubricant and crud 2. Apply some deoxit to wipers, contacts and element 3. Apply a suitable lubricant Does this sound reasonable?
From: Sjouke Burry on 15 Jul 2010 22:25 oparr(a)hotmail.com wrote: > Started a new thread since the other was getting long/convoluted/ > confusing. Even though wiping back and forth cured the wiper bounce > problem discussed in previous thread, I decided to pull the pot apart > to see what exactly caused the problem. > > The design of this particular pot is such that there are no discrete > steps as some had suggested. The helical element wire size and wiper > carrier mechanisms result in the wipers tracking the element > precisely. See this shot; > > http://www.pbase.com/eldata/image/126557137 > > Also, it's pretty obvious that this is not a "1-turn element" with > some internal planetary gear mechanism faking a 3-turn pot (as one > silly fellow adamantly suggested). More shots here; > > http://www.pbase.com/eldata/d300_wwpot > > Think I'll do the following; > > 1. Clean all parts with mineral spirits to remove any dried lubricant > and crud > 2. Apply some deoxit to wipers, contacts and element > 3. Apply a suitable lubricant > > Does this sound reasonable? Sound right, though a bit expensive. The lubricant is the iffy part, I would not know what to choose, maybe a carbon or copper filled type. I would also suggest ~1-5 nf ceramic cap between ground and wiper, providing a hold function when the wiper is a bit bouncy.
From: Artemus on 15 Jul 2010 22:41 <oparr(a)hotmail.com> wrote in message news:83133164-dd09-4463-b356-dd4d555d2f66(a)e5g2000yqn.googlegroups.com... > Started a new thread since the other was getting long/convoluted/ > confusing. Even though wiping back and forth cured the wiper bounce > problem discussed in previous thread, I decided to pull the pot apart > to see what exactly caused the problem. > > The design of this particular pot is such that there are no discrete > steps as some had suggested. The helical element wire size and wiper > carrier mechanisms result in the wipers tracking the element > precisely. See this shot; > > http://www.pbase.com/eldata/image/126557137 > > Also, it's pretty obvious that this is not a "1-turn element" with > some internal planetary gear mechanism faking a 3-turn pot (as one > silly fellow adamantly suggested). More shots here; > > http://www.pbase.com/eldata/d300_wwpot > > Think I'll do the following; > > 1. Clean all parts with mineral spirits to remove any dried lubricant > and crud > 2. Apply some deoxit to wipers, contacts and element > 3. Apply a suitable lubricant > > Does this sound reasonable? IIRC those pots are constructed with fine wire wrapped around an insulating rod that forms the major helix. Take a closer look with a magnifying glass at your wire to see if this is what you have. If yes, then you still have discrete steps in the resistance as the wiper slides along the element. Turning the knob slowly should allow the wiper to drop between 2 turns, bridging them, and give you a step response. Rapid turning can cause wiper bounce. Is the Deoxit or your lubricant conductive? Art
From: Nunya on 16 Jul 2010 00:17 On Jul 15, 7:41 pm, "Artemus" <bo...(a)invalid.org> wrote: > <op...(a)hotmail.com> wrote in message > > news:83133164-dd09-4463-b356-dd4d555d2f66(a)e5g2000yqn.googlegroups.com... > > > > > Started a new thread since the other was getting long/convoluted/ > > confusing. Even though wiping back and forth cured the wiper bounce > > problem discussed in previous thread, I decided to pull the pot apart > > to see what exactly caused the problem. > > > The design of this particular pot is such that there are no discrete > > steps as some had suggested. The helical element wire size and wiper > > carrier mechanisms result in the wipers tracking the element > > precisely. See this shot; > > >http://www.pbase.com/eldata/image/126557137 > > > Also, it's pretty obvious that this is not a "1-turn element" with > > some internal planetary gear mechanism faking a 3-turn pot (as one > > silly fellow adamantly suggested). More shots here; > > >http://www.pbase.com/eldata/d300_wwpot > > > Think I'll do the following; > > > 1. Clean all parts with mineral spirits to remove any dried lubricant > > and crud > > 2. Apply some deoxit to wipers, contacts and element > > 3. Apply a suitable lubricant > > > Does this sound reasonable? > > IIRC those pots are constructed with fine wire wrapped around an > insulating rod that forms the major helix. Take a closer look with > a magnifying glass at your wire to see if this is what you have. If > yes, then you still have discrete steps in the resistance as the wiper > slides along the element. Turning the knob slowly should allow the > wiper to drop between 2 turns, bridging them, and give you a step > response. Rapid turning can cause wiper bounce. > > Is the Deoxit or your lubricant conductive? > Art This is proof that you really do not know much about what you speak of. They are designed specifically such that more than one wire is always in contact with the wiper at any time.
From: Nunya on 16 Jul 2010 00:19
On Jul 15, 7:25 pm, Sjouke Burry <burrynulnulf...(a)ppllaanneett.nnll> wrote: > op...(a)hotmail.com wrote: > > Started a new thread since the other was getting long/convoluted/ > > confusing. Even though wiping back and forth cured the wiper bounce > > problem discussed in previous thread, I decided to pull the pot apart > > to see what exactly caused the problem. > > > The design of this particular pot is such that there are no discrete > > steps as some had suggested. The helical element wire size and wiper > > carrier mechanisms result in the wipers tracking the element > > precisely. See this shot; > > >http://www.pbase.com/eldata/image/126557137 > > > Also, it's pretty obvious that this is not a "1-turn element" with > > some internal planetary gear mechanism faking a 3-turn pot (as one > > silly fellow adamantly suggested). More shots here; > > >http://www.pbase.com/eldata/d300_wwpot > > > Think I'll do the following; > > > 1. Clean all parts with mineral spirits to remove any dried lubricant > > and crud > > 2. Apply some deoxit to wipers, contacts and element > > 3. Apply a suitable lubricant > > > Does this sound reasonable? > > Sound right, though a bit expensive. > The lubricant is the iffy part, I would not know what to choose, > maybe a carbon or copper filled type. > > I would also suggest ~1-5 nf ceramic cap between ground and wiper, > providing a hold function when the wiper is a bit bouncy. That is a good way to make a big, fuzzy wiper node on your pot, and make for odd parasitic effects. NO, conductive media at all gets put on the pot. There is no need for any deox or anti-ox either, because it is stainless or Nichrome wire. |