TrampTraceElliotPotentiometers

[hewo]

I repaired this amplifier and mistakenly sprayed Caig rejuvenator cleaner lubricant into all fourteen pots' pigtail opening.

After fifteen hours of musical duty service, the potentiometers, not all, but enough to raise concern, have crackling sounds when dialed.

So wiper ring contact is compromised by the loss of factory's shafting snug lube, and fifteen hours of vibration from the 12" speaker combo.

fiddling the shaft while "live" fixes the crackling noise, but it comes back later on.

this reveals the resistive track is ok right?

I believe what is happening is flux, debris, conductive carbon dust, factory shafting grease, all have chop suey mixed into the pot.

the pot is pretty loose rotating, it's lost it's snugness, and the speaker vibrations are ball peening the interface wiper stylus onto it's track.

I search the web for replacement pots, fourteen rectangular (Japanese alps?) shaped creatures, impossible to find.

the preamp fet's driving the potentiometers are isolated by the coupling cap, all tantalums, infamous tantalums, but they all test leakage free out of circuit (1970's era of design must be ok).

I tried replacing the one meg audio taper pot of channel two gain, using a cheapo alpha small size oriental splined, and got successful results, even under vibration duress.

trouble is the alpha mini pot must be dremel'd down to suit mobo fitup to the panel, because it's plane of pcb pigtails is indifferent from the original pot, with respect to the mounting plane (panel).

dremel'ing involves severing the pigtails flush to the substrate, then soldering new pigtails made of 1/4 watt resistor excess leads.

these leads then accommodate to the mounting plane, I guess because they are maluable.

please help locate (ebay?) these rectangular pots.

otherwise, the painstaking alternative must be performed fourteen times.

thanks in advance

[J M Fahey]

0) post where you live. Most obscure this very important point, which affects type of answers , which can go from:"junk it, you can get a new one on Craigslist for $90" (USA) to "go to the nearest Lamasery and pray"(Tibet) and anything in between, including "mod a standard 16mm pot (Argentina and many other places) .
1) post a picture of pots, which I guess are physically the same.
2) make a drawing showing measurements, as exact as possible.
Pin separation is important, because I guess they are PCB inserted.
3) with said measurements in hand, hunt Mouser , they usually show only a couple measurements in the main page but all parts have a link to the Factory datasheet.
I'm quite certain you will find something that fits in there.
Post a front panel picture, other from the inside, showing how pots are attached to PCB.
Sometimes replcing 1 or 2 is a mess, replacing *all* not that much, because they again align to each other.
4) since they are all but unusable by now, and the grime chop suey holds value in my book, *flush* them.
Pull the PCB so as not to make such a mess, put it over a newspaper, load a 5cc or 10cc syringe with plain kerosene (paraffin in the Commonwealth) and literally flush each of them, through any visible opening, moving them end to end.
Do it a couple times, so the kerosene wave is certain to carry any filth and grease away.
You may wait a couple hours or overnight for kerosene to drip off and remains evaporate and then apply any pot cleaner you like which leaves lubrication behind, if you wish.

Naphta, ligher fluid, etc. may attack plastics or carbon track binder, kerosene is weakest solvent which still works and does not attack plastics.
Legal disclaimer : everything is usually written in such cases

[Enzo]

Yes. Use a proper cleaner and reclean the things. If the first round loosened up gunk, now blow that out with fresh cleaner.

Even your shampoo bottle says "lather, rinse, and repeat."


You want help with parts? Then tell us what model amp you are servicing, we can't just guess. If the pots are rectangular, are they 12mm, 14mm 20mm? some other mm? Horizontal or vertical mount? SOlid shaft, D shaft, split shaft, smooth shaft, knurl shaft, John Shaft. ("I'm just talkin" "bout Shaft") And so on.

[J M Fahey]

SOlid shaft, D shaft, split shaft, smooth shaft, knurl shaft, John Shaft. ("I'm just talkin" "bout Shaft") And so on.

You're RIGHT!!
How could I forget !!!:

[hewo]

will photograph removed pot

Yes. Use a proper cleaner and reclean the things. If the first round loosened up gunk, now blow that out with fresh cleaner.

Even your shampoo bottle says "lather, rinse, and repeat."


You want help with parts? Then tell us what model amp you are servicing, we can't just guess. If the pots are rectangular, are they 12mm, 14mm 20mm? some other mm? Horizontal or vertical mount? SOlid shaft, D shaft, split shaft, smooth shaft, knurl shaft, John Shaft. ("I'm just talkin" "bout Shaft") And so on.

Will cellphone camera pics of removed pot, oriental splined short shafting, so maybe "alps"?

There's a hightech racing bicycle lube for the chain that penetrates but thoroughly dries out into residual non-wet lube, so as to resist dust attraction.

Maybe I could re-snug said shaftings merely by introducing such film deposit, easily accessible shafting to bushing interface.

[Enzo]

Plain old Deoxit ought to clean up 99.9% of noisy pots. Bike chain lube might leave a dry residue, but that doesn't mean it is electrically benign.

Alps is a brand, but most makers make all the basic shapes and sizes. I look for the type, not the brand.

[hewo]

dryfilm lube

Plain old Deoxit ought to clean up 99.9% of noisy pots. Bike chain lube might leave a dry residue, but that doesn't mean it is electrically benign.

Alps is a brand, but most makers make all the basic shapes and sizes. I look for the type, not the brand.

The intent is to apply only enough for the shafting interfacing its bushing sleeve.

Too much will intrude into electrically energized portions.

I should test the residual for electrical properties. There is no graphite, no carbon, no moly, appears as ivory as in tusq.

[hewo]

here are the photographs and forum please delete this ftp disclosure confidence (30Mb) thanks, pots are exactly 1/2 british inches square measurement, yet spline is oriental just like alpha pots. i was pondering maybe the knob removal tension force slightly loosened the swedging flare on the pot's backside substrate. the swedging is intended to lock the shafting to the inner substrate, permitting rotation. notice that the outer substrate is not afforded any means to remove. there are bear claws casted of aluminum that can not be bent open to release the outer substrate.

ftp://cchftp1.honolulu.gov/pots.pdf
account cchftpuser
password cchftpuser

[drewl]

Yeah, you have to remove the knob a special way.
Pop the colored cap off and you will see a screw that has to be removed, then the knob comes off.

Don't ask me how I know this!

[Jazz P Bass]

Been there, done that!

[olddawg]

As mentioned before plain old Caig Dioxit should flush out and lube the pots. And also as previously said, do it with the chassis out and use a cloth rag, paper towels or whatever to catch any excess and mess. If you have previously flushed the pots with tuner cleaner or a solvent that has removed all of the shaft grease and you want that factory "tight" feel, you may have to disassemble the pots to regrease the shaft.

[hewo]

caig spray called deoxit rejuvenator cleaner lubricant corrosion protection

I generously injected caig using needle straw nozzle into the pigtail openings of all fourteen pots.
Lots of clear clean caig drained out from each and every escape opening of each pot.
I did not see any offending contaminants being flushed out.
Of course who's to say contaminants must be visibly macroscopic.
Eagerly, I reassembled to conclude results.
Yes, the caig residual keeps the wiper stylus engaged connectivity to its track conductive interface.
Must be self healing overlay recovery as stylus swooshes through it, analogous to rainwater returning over tire run pavement.
I did not restore the plastic knobs. I applied tiny droplet of said hightech bicycle dry chain lube to shafting daylight opening at bushing. Then must orbital motion shafting using fingers, not rotate but orbital pinch. This wicks the liquidous phase deep into shafting bushing clearance. As lube volatile liquid evaporates, the residual begins to afford shafting rotational friction, which is desired insofar as ergonomically suitable. This hightech lube boasts longevity and lubricity and harmlessness. It is very anti-viscous, penetrating properties. Conceivably, it's not good if it contaminates conductive interfaces, so that's why one tiny drop sparingly on application.
Result: back in musical business!
The caig actually lowers the resistive track value, e.g., the 50k becomes 45k, practically indecernable, but will likely rise as caig depletes over time. The scratchy crackling is no more. Maybe I should thoroughly recheck that pot removed as shown in pics, that oddball alpha pot replacement.

[g1]

Did the chain wax restore the stiffer feel of the rotation to be more like the pots would feel when new?

[Enzo]

Actually I prefer my pot shafts to be real slippery. Kinda like I prefer my...

[hewo]

joker, yes and no to your answer requested.
I don't know why certain pots got snugly whilst some only small change of snugly targeted.
Do note these pots are reminiscent of the unrestrictive past quality productions of pots, these have those tempered wavy washers used on guitar Schaller tuning machines to preload button axle tension onto worm crown gearing interface. There is no axial play on these pots axis. So I was wrong insofar as destroying the rigid shafting swaging peened on the inner substrate.
There also may be some time delay for the chain volatile to escape tight tolerances, and later snugness may appear.