Anyone replace pots with presets ?

[N Cook]

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)

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

Thanks for that, I had not considered the end stops.
The original one, with the flimsey wiper, had quite manly endstop nib on the
shaft and housing moulding.
These presets have similar sized physical end stops, the weakest point would
be the two plastic pauls on the shaft that engage with the slot, about 3 x
1.5mm each in cross section.
I would mount the body to pcb with hot melt glue.
Guitarists and pot problems is usually the guitar controls where the fascia
is plastic so no reliable mounting, so the nuts loosen and pots are then
twisted round and round , windlassing the wires into a broken mess.
That problem I cure by heavy-soldering a thick copper strip between all the
pots, replacing the wire grounds between the pots

 

[Michael A. Terrell]

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?

Groupie is a group of enthusiastic fans of any type, in the US.

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.

They referred to them as bands, and their electronics as "Band Amps",
"Musical equipment" or "Guitar amps" when I was doing that work in the
'70s & '80s. Most repairs were done by part time techs at music stores,
but there was usually a
shop that specialized in amp repair in bigger cities. I even saw a few
british amps, back in the '70s when some clueless wanabes were trying to
copy one band or another, right down to the brand of wire and connectors
for their cables. The only thing they forgot was to learn how to play
music, sing, and perform in front of people who want good music. ;-)

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 ...

As far as I am concerned, panel mounted controls are the only way to
go for any application that involves rugged service. PC mounted are ok
for internal adjustment, but nothing beats a mil spec made to last for
25 years of daily use.

--
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

 

[James Sweet]

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.

What difference does it make? Cheap pots are cheap pots. I was
originally using ones from Radio Shack, but those were not holding up
even to home use.

 

[**THE-RFI-EMI-GUY**]

Seems kind of unlikely that equipment like that would get a lot of wear
from the pots being adjusted back and forth. Could it be that vibration
from the speakers is tearing up the pots in the head? Maybe the PC board
and front panel lack the mechanical dampening to protect this from
happening.

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.

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P

 

[**THE-RFI-EMI-GUY**]

That explains the problem. What he needs to do is follow the group out
to the "Gig". He doesn't need to be there from the start, rather at the
end when the group finishes up by smashing their guitars and mike stands
into his rental amplifiers!

:




Musical Instrument amplifiers and the like.

Graham

That explains the problem. What he needs to do is follow the group out
to the "Gig". He doesn't need to be there from the start, rather at the
end when the group finishes up by smashing their guitars and mike stands
into his rental amplifiers!

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P

 

[N Cook]

Seems kind of unlikely that equipment like that would get a lot of wear
from the pots being adjusted back and forth. Could it be that vibration
from the speakers is tearing up the pots in the head? Maybe the PC board
and front panel lack the mechanical dampening to protect this from
happening.



--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P

Its not a wear problem , in my opinion.
There is absolutely no wear on the track , the problem is due to too flimsy
a wiper, half an ounce of pressure is enough to start lifting the wiper, ie
only age-thickened lubricant grease inside is enough to do that.

 

[Arfa Daily]

Its not a wear problem , in my opinion.
There is absolutely no wear on the track , the problem is due to too
flimsy
a wiper, half an ounce of pressure is enough to start lifting the wiper,
ie
only age-thickened lubricant grease inside is enough to do that.

But surely that's the age-old problem of any pot ? Isn't that why we all
squib decent quality switch cleaner into pot bodies ? The volatile component
of this dissolves and washes out the hardened grease, whilst the lubricant
component recoats the track. Thinking about your statements regarding wiper
pressure. The wiper has to have reasonably light contact with the track in a
user-intended control, otherwise constant adjustment, would wear the track.
It seems to me that a half ounce of contact pressure, is quite a lot ? For
sure, the big old clunky pots that were fitted to gear 40 years ago,
probably had a wiper the size of your hand that pressed on a track as thick
as your finger with a pressure of half a pound, but times and manufacturing
techniques move on. Just exactly what problems do you seem to get with all
these pots, that won't fix with a shot of Electrolube ? With the shaft
encoders that many hifi's use now for volume control, I've found that the
grease which appears on the encoder disc, and stops then from working, is
the treacle-stir-feel grease that they put in the shaft bearing, which has
migrated down into the main body. The wipers in these devices are like
feathers, and very delicate, but once they are cleaned out, and relubed with
a proper contact lubricant, they don't give any more trouble - in fact I
can't recall ever having one thus treated, bounce back on me.

Arfa

 

[Ron(UK)]

Its not a wear problem , in my opinion.
There is absolutely no wear on the track , the problem is due to too flimsy
a wiper, half an ounce of pressure is enough to start lifting the wiper, ie
only age-thickened lubricant grease inside is enough to do that.

It`s the age old problem of cheap nasty low cost components being used,
even in some equipment perceived as being of high status. You CAN buy
decent pots if you shop around, or use normal replacement pots and add a
drop of electrolube to the track before you solder it in.

I wouldn`t advise changing too many components in some muso`s vintage
gear, some of these valve amp afficionados get shirty if you replace
faulty resistors with modern types that 'don't look right' I hate to
think what they`d say if you added a bodged up pot


Ron(UK)

 

[N Cook]

I'm coming round to thinking that as these pots are easily openable and
there is no wear at all on the tracks, then clean out all the lubricant with
meths or something, coat the wiper with something to stiffen it up a bit and
re-assemble, with no lubricant at all, maybe just "dry lubricant" of fine
graphite powder laid in the track area instead.

 

[N Cook]

But surely that's the age-old problem of any pot ? Isn't that why we all
squib decent quality switch cleaner into pot bodies ? The volatile component
of this dissolves and washes out the hardened grease, whilst the lubricant
component recoats the track. Thinking about your statements regarding wiper
pressure. The wiper has to have reasonably light contact with the track in a
user-intended control, otherwise constant adjustment, would wear the track.
It seems to me that a half ounce of contact pressure, is quite a lot ? For
sure, the big old clunky pots that were fitted to gear 40 years ago,
probably had a wiper the size of your hand that pressed on a track as thick
as your finger with a pressure of half a pound, but times and manufacturing
techniques move on. Just exactly what problems do you seem to get with all
these pots, that won't fix with a shot of Electrolube ? With the shaft
encoders that many hifi's use now for volume control, I've found that the
grease which appears on the encoder disc, and stops then from working, is
the treacle-stir-feel grease that they put in the shaft bearing, which has
migrated down into the main body. The wipers in these devices are like
feathers, and very delicate, but once they are cleaned out, and relubed with
a proper contact lubricant, they don't give any more trouble - in fact I
can't recall ever having one thus treated, bounce back on me.

Arfa

I'm not sure that aerosol lubricant would reliably get into these pots ,
there certainly isn't any slots and I would say the injection mouleded 2
components of the housing are tight fitting. There is still the sludgy
lubricant grease inside.

 

[Arfa Daily]

I'm coming round to thinking that as these pots are easily openable and
there is no wear at all on the tracks, then clean out all the lubricant
with
meths or something, coat the wiper with something to stiffen it up a bit
and
re-assemble, with no lubricant at all, maybe just "dry lubricant" of fine
graphite powder laid in the track area instead.

Ah ! Same post appeared ( accidentally I guess ) in your "speaker power"
thread, so I say the same here -

There ya go then !

I also agree with Ron in respect of subbing parts in musos' gear. Looking
for trouble with some of them ...

Arfa

 

[N Cook]

Ah ! Same post appeared ( accidentally I guess ) in your "speaker power"
thread, so I say the same here -

There ya go then !

I also agree with Ron in respect of subbing parts in musos' gear. Looking
for trouble with some of them ...

Arfa

Rushing around to go to a pyrotechnics lecture.
Interesting demonstratiion of a developemental stage pyrotechnic strobe
light, for chemistry , amazingly sharp cut-off, re-ignition, of about 4
flashes per second, intense flare strobe action