Anyone replace pots with presets ?

[N Cook]

Ten years ago I would have considered it impractical or even immoral.
But having to replace yet another effectively all plastic 12 mm pot because
the wiper is almost invisible in thickness, perhaps time for a rethink.
This type of pot has a metal covering but its only function is as a shroud
for fixing to the board, not even earthed, it does not strengthen the pot
body to restrain abuse at the other, user end. No longer are such pots fixed
to the front pannel.
I'm thinking that with the next one to replace it will be with a standard
small 12 mm or so enclosed preset that takes a standard plastic shaft in the
adjustment slot, fudging the other end of the shaft to take the knob and
through pannel bearer. The internal mechanism is just a pro-rata scaled down
conventional paxolin backed track with double wiper nibs.
If this replacement physically breaks in use then that seems more
justifiable than the modern flimsy wipers losing spring action or just aging
of the lubricant inside to wedge under the wiper and loose contact or
whatever their problem is, the tracks are always perfect (so little wiper
pressure presumably).
Are the resistive tracks of presets more frail/easier scoored than pot
tracks, so for that reason cannot be used say for volume control ?
Anyone any opinions?

 

[Arfa Daily]

Ten years ago I would have considered it impractical or even immoral.
But having to replace yet another effectively all plastic 12 mm pot
because
the wiper is almost invisible in thickness, perhaps time for a rethink.
This type of pot has a metal covering but its only function is as a shroud
for fixing to the board, not even earthed, it does not strengthen the pot
body to restrain abuse at the other, user end. No longer are such pots
fixed
to the front pannel.
I'm thinking that with the next one to replace it will be with a standard
small 12 mm or so enclosed preset that takes a standard plastic shaft in
the
adjustment slot, fudging the other end of the shaft to take the knob and
through pannel bearer. The internal mechanism is just a pro-rata scaled
down
conventional paxolin backed track with double wiper nibs.
If this replacement physically breaks in use then that seems more
justifiable than the modern flimsy wipers losing spring action or just
aging
of the lubricant inside to wedge under the wiper and loose contact or
whatever their problem is, the tracks are always perfect (so little wiper
pressure presumably).
Are the resistive tracks of presets more frail/easier scoored than pot
tracks, so for that reason cannot be used say for volume control ?
Anyone any opinions?

I would have said that the description " preset " tells you all that you
need to know on that score. These components are designed to be set and
left, pretty much for the lifetime of the equipment, so I can't see them
standing up to the rigours of regular use for long. Add to this that as they
are not designed to be rotated repeatedly as a user control, the wiper /
track interface has not been designed to be specifically quiet. I also think
that the control will feel bad to a user, as it will not have that "
stirring treacle " feel that a proper user control has, courtesy of the drag
grease that the manufacturers put in the spindle bush. Why not replace
controls with manufacturer's originals ? Most group amp builders supply
spare parts. Failing that, there are plenty of reasonable quality pots
available - even the range that Maplin keep are pretty fair quality - and if
you really want to fit top quality pots, these are also available from
audiophile outlets.

Arfa

 

[N Cook]

I would have said that the description " preset " tells you all that you
need to know on that score. These components are designed to be set and
left, pretty much for the lifetime of the equipment, so I can't see them
standing up to the rigours of regular use for long. Add to this that as they
are not designed to be rotated repeatedly as a user control, the wiper /
track interface has not been designed to be specifically quiet. I also think
that the control will feel bad to a user, as it will not have that "
stirring treacle " feel that a proper user control has, courtesy of the drag
grease that the manufacturers put in the spindle bush. Why not replace
controls with manufacturer's originals ? Most group amp builders supply
spare parts. Failing that, there are plenty of reasonable quality pots
available - even the range that Maplin keep are pretty fair quality - and if
you really want to fit top quality pots, these are also available from
audiophile outlets.

Arfa

I had not considered the feel, which agreed is very 'scratchy'.
Squirting silicone oil in one and turning back and forth a hundred times is
very much improved, and resistive track still ok.
What is the point of the feather-light touch of the flimsy pots if the
downside is they just don't last.
I don't see the point of replacing with an exact match when the original is
say one of 8 and has only lasted for use once a week for 2 years before
internally failing , ie not abuse. In fact they seem to be the pots that are
not used much if at all, that's why I suspect clumping or something in the
lubricant.
I'll try a 1000 times and re-measure to see if the track fails.

 

[Arfa Daily]

I had not considered the feel, which agreed is very 'scratchy'.
Squirting silicone oil in one and turning back and forth a hundred times
is
very much improved, and resistive track still ok.
What is the point of the feather-light touch of the flimsy pots if the
downside is they just don't last.
I don't see the point of replacing with an exact match when the original
is
say one of 8 and has only lasted for use once a week for 2 years before
internally failing , ie not abuse. In fact they seem to be the pots that
are
not used much if at all, that's why I suspect clumping or something in the
lubricant.
I'll try a 1000 times and re-measure to see if the track fails.

--

I'm actually really surprised that you seem to come across so many bad pots
in group amps. I have been repairing these for many many years, and do lots
of all makes and models, for a local shop, and I really don't have to
replace many pots that aren't physically broken through taking knocks. I
have found in general, that most manufacturers appreciate that this gear is
going to last its owners for a lot of years, and tailor their design
criteria, and component spec-ing to suit. I would agree that the pots fitted
these days tend to be Japanese ( probably Chinese actually ) small-bodied
types, which are not as good quality as say the large body Wellyns or the
typical RS components pots that you used to find in them a few years back,
but still, I don't seem to have that much trouble with them. If you really
think that the problem is insufficient spring tension on the wiper fingers,
just pile a bit more on. It's easily done with a pair of long-nosed pointy
surgical tweezers.

Arfa

 

[N Cook]

I'm actually really surprised that you seem to come across so many bad pots
in group amps. I have been repairing these for many many years, and do lots
of all makes and models, for a local shop, and I really don't have to
replace many pots that aren't physically broken through taking knocks. I
have found in general, that most manufacturers appreciate that this gear is
going to last its owners for a lot of years, and tailor their design
criteria, and component spec-ing to suit. I would agree that the pots fitted
these days tend to be Japanese ( probably Chinese actually ) small-bodied
types, which are not as good quality as say the large body Wellyns or the
typical RS components pots that you used to find in them a few years back,
but still, I don't seem to have that much trouble with them. If you really
think that the problem is insufficient spring tension on the wiper fingers,
just pile a bit more on. It's easily done with a pair of long-nosed pointy
surgical tweezers.

Arfa

The present problematic is a Carvin Pro Bass 100, PB100 which will come
bouncing back next weekend.
The new fault , could well be due to another pot failed, symptoms over the
phone so far, the previous one I replaced is fine.
I still have the previous original one lying around .
No makers name , a logo like cross-section of a flying saucer, a thin elipse
laid over a circle, just the outermost lineforms.
The wiper is only 0.15 mm thick , 0.6mm wide and using a force gauge, it
starts deflecting at only 12 grams pressure.

Followup on my endurance test on a preset, I survived 1000 turns back and
forth , whole track, as did the pot. No wavering on mid-track resistance
readings. The rough feel has returned but I doubt that is due to the wiper
action. Cracking it open, one obvious shiny, but not broken through to
paxolin, track from one nib and vague partial thin trace from the other nib.
I would estimate it could have done more than 10,000 rotations before both
tracks were worn through.

 

[Arfa Daily]

The present problematic is a Carvin Pro Bass 100, PB100 which will come
bouncing back next weekend.
The new fault , could well be due to another pot failed, symptoms over the
phone so far, the previous one I replaced is fine.
I still have the previous original one lying around .
No makers name , a logo like cross-section of a flying saucer, a thin
elipse
laid over a circle, just the outermost lineforms.
The wiper is only 0.15 mm thick , 0.6mm wide and using a force gauge, it
starts deflecting at only 12 grams pressure.

Followup on my endurance test on a preset, I survived 1000 turns back and
forth , whole track, as did the pot. No wavering on mid-track resistance
readings. The rough feel has returned but I doubt that is due to the wiper
action. Cracking it open, one obvious shiny, but not broken through to
paxolin, track from one nib and vague partial thin trace from the other
nib.
I would estimate it could have done more than 10,000 rotations before both
tracks were worn through.

In that case, go for it. I would be interested to know how you get on with
such transpants, and which presets you ultimately find most suitable. Also,
how quiet they are in actual practical usage.

Arfa

 

[Ron(UK)]

In that case, go for it. I would be interested to know how you get on with
such transpants, and which presets you ultimately find most suitable. Also,
how quiet they are in actual practical usage.

Arfa

I'm interested to know how the OP plans to reliably connect a standard
shaft to a preset, I`m presuming his idea of a preset and mine concur.

One other point, presents don`t normally come in log tapers, do they?

Ron(UK)

 

[Arfa Daily]

I'm interested to know how the OP plans to reliably connect a standard
shaft to a preset, I`m presuming his idea of a preset and mine concur.

One other point, presents don`t normally come in log tapers, do they?

Ron(UK)

Hi Ron. That is a very good point, and one that I hadn't even considered
when thinking about his original plan to use these. If you look in the post
that started the thread, he says that he is intending using the presets that
you can get a 6mm shaft for that turns them into a ( semi ?? ) user
control - I'm sure you've seen the idea on stuff where there is an
adjustment that would be a good idea to have available to the user, but not
in a way that encourages him to *use* it. The shafts that I've seen usually
have a lightly splined finish so that they can be gripped, and a screwdriver
slot in the end. I think he intends to pass one of these through a panel
mount shaft bush, and then persuade the knob to fit.

Arfa

 

[N Cook]

I'm interested to know how the OP plans to reliably connect a standard
shaft to a preset, I`m presuming his idea of a preset and mine concur.

One other point, presents don`t normally come in log tapers, do they?

Ron(UK)

I should have said the failed original in the 0.6mm was 2 wipers , the metal
is split into 2 wipers and nibs, absolutely no trace of wear on the track.

I have a few hundred Piher presets that have an enlarged slot to take rod
extenders with pair of pauls to engage the back of the slot, quite strong
enough to be used as unabused pots.
The very light action of the originals I would have thought were a
disadvantage, on stage, as you could easily dislodge a neighbouring pot.
Some of these Piher presets are log tracks, agreed unusual but useful

 

[Ron(UK)]

Hi Ron. That is a very good point, and one that I hadn't even considered
when thinking about his original plan to use these. If you look in the post
that started the thread, he says that he is intending using the presets that
you can get a 6mm shaft for that turns them into a ( semi ?? ) user
control - I'm sure you've seen the idea on stuff where there is an
adjustment that would be a good idea to have available to the user, but not
in a way that encourages him to *use* it. The shafts that I've seen usually
have a lightly splined finish so that they can be gripped, and a screwdriver
slot in the end. I think he intends to pass one of these through a panel
mount shaft bush, and then persuade the knob to fit.

Arfa

Ah ok, Piher do a range of shafts for their min presets. I`ve used them
on radio mike receivers etc. to replace the output level and squelch
controls, invariably because the user has been heavy handed with them.
The combined cost of preset and shaft is quite high compared with a
normal pot.

Personally I like the Omeg ECO plastic pots for replacements on gear
that takes standard quarter inch bore knobs, Rapid Electronics stock
the pots with the monkey metal slotted and splined short shaft that fits
a lot of the Chinese product

Ron(UK)

 

[Eeyore]

I'm interested to know how the OP plans to reliably connect a standard
shaft to a preset, I`m presuming his idea of a preset and mine concur.

One other point, presents don`t normally come in log tapers, do they?

Never IME.

Graham

 

[N Cook]

Ah ok, Piher do a range of shafts for their min presets. I`ve used them
on radio mike receivers etc. to replace the output level and squelch
controls, invariably because the user has been heavy handed with them.
The combined cost of preset and shaft is quite high compared with a
normal pot.

Personally I like the Omeg ECO plastic pots for replacements on gear
that takes standard quarter inch bore knobs, Rapid Electronics stock
the pots with the monkey metal slotted and splined short shaft that fits
a lot of the Chinese product

Ron(UK)

--
Lune Valley Audio
Public Address Systems
Hire Sales Maintenance
www.lunevalleyaudio.com

If you mean the Vishay 12/13mm footprint pots then they are the right size
but the manufacturer's pdfs don't give the wiper dimensions , if of
thickness of a coarse human hair , 150 microns, then little point in using,
as will be back to square 1 in a few years.

 

[Ron(UK)]

If you mean the Vishay 12/13mm footprint pots then they are the right size
but the manufacturer's pdfs don't give the wiper dimensions , if of
thickness of a coarse human hair , 150 microns, then little point in using,
as will be back to square 1 in a few years.

I didn't, I meant Omeg, but the Vishay pots will certainly be better
than anything fitted as an original part by the vast majority of
manufacturers.

Ron(UK)

 

[James Sweet]

Hi Ron. That is a very good point, and one that I hadn't even considered
when thinking about his original plan to use these. If you look in the post
that started the thread, he says that he is intending using the presets that
you can get a 6mm shaft for that turns them into a ( semi ?? ) user
control - I'm sure you've seen the idea on stuff where there is an
adjustment that would be a good idea to have available to the user, but not
in a way that encourages him to *use* it. The shafts that I've seen usually
have a lightly splined finish so that they can be gripped, and a screwdriver
slot in the end. I think he intends to pass one of these through a panel
mount shaft bush, and then persuade the knob to fit.

Arfa

It's really a moot point though. One can still buy very high quality
pots from a reputable manufacture. That's the route to take rather than
trying to hack in something different. A good pot will last the life of
most equipment. I use Bournes pots in arcade game controllers, they seem
to hold up well to the abuse.

 

[Arfa Daily]

It's really a moot point though. One can still buy very high quality pots
from a reputable manufacture. That's the route to take rather than trying
to hack in something different. A good pot will last the life of most
equipment. I use Bournes pots in arcade game controllers, they seem to
hold up well to the abuse.

Hi James. That was my original feeling also, but as I said further up, I
repair lots of group equipment, and really don't seem to suffer that much
from bad as opposed to broken pots, anyway.

Arfa

 

[Michael A. Terrell]

Hi James. That was my original feeling also, but as I said further up, I
repair lots of group equipment, and really don't seem to suffer that much
from bad as opposed to broken pots, anyway.

What do you mean by "Group equipment"?


BTW, http://potentiometer.com/ carries high end commercial & military
grade pots in the US.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Eeyore]

What do you mean by "Group equipment"?

Musical Instrument amplifiers and the like.

Graham

 

[N Cook]

It's really a moot point though. One can still buy very high quality
pots from a reputable manufacture. That's the route to take rather than
trying to hack in something different. A good pot will last the life of
most equipment. I use Bournes pots in arcade game controllers, they seem
to hold up well to the abuse.

The thread concerns 12/13 mm footprint pots (sub miniature), no problem with
17mm miniature or 21mm standard size ones. I doubt game controllers use
subminiature ones.

 

[Ron(UK)]

The thread concerns 12/13 mm footprint pots (sub miniature), no problem with
17mm miniature or 21mm standard size ones. I doubt game controllers use
subminiature ones.

One thing that concerns me about using a preset as a user control is the
'end stop' arrangement. Is the mechanism that prevents a user from
turning the control past it`s fully on or fully off position rugged
enough on a preset to to the job considering what heavy handed users
there sometimes are in the music business.

Also, if the end stop IS strong enough, is the mounting arrangement of a
preset strong enough to withstand the turning force of a typical death
metal guitarist after several pints of Krugermeister?



Ron(UK)

 

[Arfa Daily]

What do you mean by "Group equipment"?

Er, equipment used by groups ? Like bands ? Beatles, Rolling Stones ? Do you
not call them "groups" your side of the pond ? Never heard the term
"groupies" for the girls that follow them around ? In terms of this thread,
we have been talking specifically amplifiers for musical instruments, but in
general, at least over here, "group equipment" covers anything that a group
or band may be using on stage ( or off-stage ) to make their sound or image,
so amps, mixer desks, effects units / pedals, wireless mics, lighting
effects and so on. I know from our past
- errr ... 'conversations' shall we say - that you have been involved in the
repair of this equipment, so I'm sure that you probably have a valid opinion
on the substituting of panel-type pots with presets made into panel mounting
types ?? Back to you, friend ...

Arfa