Fishman SA220 - Dirty pots?..try this first

[Seeker]

Howdy,
I recently cleaned the pots on my 1975 Yamaha g100 412.  I truly thought the bass pot was shorted out given the symptoms. I could not believe the results from a good cleaning..like brand new now.  So my Fishman SA 220 was having the same issues when I adjusted the treble on channel #1...the clip light even came on.  But after reading numerous post I really did not want to disassemble the amp(sounds like quite the process after reading other posts) to try cleaning the pot.  So I thought I would try the following.  I took a piece of 1/4 inch (inside diameter) clear tubing and cut off 1/2".  I unscrewed the nut holding the pot to the "face-plate".  I gently "screwed" the tubing over the treads on the pot till it tightened up (bottomed out).  I used the "factory cut" on the tube because it was a perfect 90 degrees to insure a good seal when it "bottomed out".  Then I inserted the red straw of the contact cleaner down along the side of the shaft, tightly held a piece of tissue around the top to reduce the amount of cleaner escaping  and sprayed. In between spays I rotated the shaft. After 3 good spray I checked it out...did not solve my problem.  I repeated the process two more times and wow..it finally worked. I did notice the pot feels..hmmm..."dry" compared to the other controls.  I'm assuming the cleaner removed any lubricant there may have been on the shaft and this may be the reason it took so many attempt to finally get it to work.....but it worked and I did not have to dissemble the amp.  The amp was used 20 hours in the past week and no return of the problem.  Just one word of caution...wear safety glasses...and of course read the label.  I'm building a better version of the clear tubing "tool"  It is sealed at one end and the red straw is  super glued through a small hole in the side.  This should provide more pressure, forcing the cleaner into the pot past the shaft.  Hopefully I will not need to try it out for a while.
Have a great day.   
PS:I hope my instructions were easy to decipher.

[galaxiex]

Nice work and thanks for the tip!
BTW you can get pot cleaning spray that has lubricant in it.

[Enzo]

Our luthier used to have a product called something like a "Gozinta" which worked the same way.  It was a hollow tube with actual threads on one end to match the standard pot threads.  It tapered to a close at the top, and had a little red tube coming out, that you plugged into your spray can hole.

Push the spray can valve and the fluid flows down the tube and gozinta the control.

[galaxiex]

addendum to this about pot lubrication.

I read somewhere that (some? many? all?) new pots have some type of grease on the shaft where it passes thru the bushing.
The grease is there for lube obviously, but also to give the pot some "feel" when turning it.

Thus if the grease gets flushed out, the pot may become "looser" and have a different feel, and be quite easier to turn.
Some pots (CTS) can be ordered sans grease for guitar controls where the player wants the pot to turn very easy for fast easy vol and/or tone swells.
This would seem to indicate the grease used is fairly thick.

I do know on some older guitars that I have picked up on ebay the pots are very stiff from lack of use.
The grease has hardened over time and flushing them out and working the pot loosens them up.

[J M Fahey]

I had custom pots made many times.

Good quality but felt "cheap/raspy" when compared to "imported " ones, so we tried many kinds of grease between shaft and bushing.

*Any*  grease was an improvement, even the first one we tried (simply because a pot was sitting on the bench for some other use) : red Lithium grease . Reasonably good but weakened along time.
Then tried standard yellowish/brownish general purpose grease, then grey/blackish graphite loaded type (also similar Molykote loaded) , absolute best was some kind of greenisk "sticky grease" (imagine that)  specially designed for ball bearings, even if displaced by pressure or movement it travels back to maximum friction point ... what the Doctor recommended, while most others tend to go somewhere else.
Second best was some whitish/translucent Dow Corning "silicone vaseline" , I think it's popular to lubricate tape recorders and such.

In a nutshell: "not all grease is the same".

[Seeker]

One thing about the pots on this Fishman, unlike other pots I've worked on, is that the shaft going into the pot is smaller than the part of the shaft the nob slides over. There is a portion of the shaft (with no "splines") approx a 64th of an inch long that butts up tight against the threaded part of the pot. These two parts have the same diameter. (I've never noticed this on pots before) This would make it impossible to lubricate unless it was taken apart (if it's even meant to be taken apart).  Other pots you could simply spay/drip in a lubricant.  I guess an important question to ask is.... when you clean a pot from the front (as I did) do you risk contaminating the pot with the pre-existing lubricant,  Or simply put, will it hurt it's performance?
Seeker

[DrGonz78]

From my experience I had an issue with slider pots and the lubricant inside some on an old Boss pedal. Sure this might be a different type of pot but lubricant is the point here. I sprayed some Deoxit F5 into the slider pot and it had a horrible reaction to the lubricant. Perhaps it was such that the lubricant had aged badly and mixing the Deoxit made it just go to a nasty sludge. The slider just got all hard and was jammed up easily. I had to completely clean out the slider and lubricate the thing up again, never got fully back to what would be normal. After cleaning regular style pots from the front shaft side it always ends up way to loose usually. Can't think of a time that the grease caused a similar problem like the time with the slide pots on the Boss pedal. I imagine though that there is a lot of dirt that builds up in the grease around the shaft. Spraying that into the pot might lead to having to spray it a couple times.

As a side note, when cleaning slide pots I never ran into that issue until cleaning the ones on the Boss pedal, but apparently slide pots can be a real pain in the butt.

[gbono]

I've wondered if this would work for restoring a nice feel to recently cleaned pots and trimers - if I can find my tube I'll try some in some clean but "crunchy" faders........

http://lufteknic.myshopify.com/products/bosch-distributor-grease-225ml