"N Cook" wrote in message
...
**THE-RFI-EMI-GUY** wrote in message
...
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.

N Cook wrote:








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.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/






--
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.



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