How to non-destructively clean RV4/Sealed/Mil style potentiometers

[SoulFetish]

Sealed Potentiometers pose a challenge when they get older and begin to show signs of aging. Inevitably, they still can get dirty and noisy, displaying that symptomatic "scratchy" sound when rotating the actuator. *Randall Aiken has an interesting write-up about having used these types of pots, as well as non-sealed types over an 18 year perspective in the Q&A section of his tech pages:
Technical Q&A
In his Q&A, he brings up valid pros and cons about using these kinds of pots. In spite of the cons of using sealed pots, I still like to use them for all the benefits he brings up. Plus, I do like the rugged construction, and the way they look in an amplifier. Hey, I'm a sucker for presentation.
While they obviously aren't as easy to clean as CTS/Alpha style pots, they certainly don't need to be discarded. While a little bit of work and some care, they can be cleaned and restored without damaging them. Here is how I do it:
Here are a few examples of RV4/Mil style sealed potentiometers


First I take a small tool (in this case, a small eyeglasses repair screwdriver) and gently wedge it under the tabs securing the back of the pot.



Then, using the same tool (or slightly larger screwdriver), I carefully leverage a little bit of space by slightly pushing the tab up and away from the body. Be cautious not to damage the finish or molding.



Do not overly bend the tabs, you only need about this much clearance.



continued below...

[SoulFetish]

Continued....

After you repeat the process on the other side, gently lift and the molded top should easily separate from the back. You only need a small opening which you can access with Deoxit spray or your contact cleaner of choice. Try not to remove the back completely, as it becomes easier to damage the internal parts.




After cleaning, gently press the pot into the cover. It should slide securely back onto the fitting.



You can improvise for this next part. I'm using a small marble trophy base, but a small block of hardwood would work fine. From the bottom up to the top, press the tabs back into place securing the cover back on and reseal the body of the potentiometer. **I would avoid using pliers for this, I don't find they work very well and you can risk damaging the pot.



with one side done, repeat the process on the other side



After that, you're finished. You're pot should be good as new



It's really not all that much work (I don't think), and would probably take longer to read this post than to clean one of these.
Now, I know the question that you all must be asking:
"This is well and good 'n all, but is this gonna' be enough to get Randall Aiken back on the RV4 bus??"
Sadly, I fear we may have lost him to Alpha's for good. C'est la vie, I suppose.

[Mick Bailey]

I find that when these pots go scratchy I can get a little cleaner/lube to 'creep' onto the track. I look around the edge of the casing and see where it's got the most chance of getting in and squirt the edge, then rotate the pot and repeat. Mostly this will work if the pot is just beginning to deteriorate. If it doesn't then it's down to loosening the shell as you describe. I call these enclosed rather than sealed - the military spec sealed ones can be fully immersed and are truly sealed with gaskets and O rings so my method won't work.

[SoulFetish]

I find that when these pots go scratchy I can get a little cleaner/lube to 'creep' onto the track. I look around the edge of the casing and see where it's got the most chance of getting in and squirt the edge, then rotate the pot and repeat. Mostly this will work if the pot is just beginning to deteriorate. If it doesn't then it's down to loosening the shell as you describe. I call these enclosed rather than sealed - the military spec sealed ones can be fully immersed and are truly sealed with gaskets and O rings so my method won't work.

While these do meet RV4 mil specs (at least the PECs definitely do), I’ve also seen a variation in the degree to which they are sealed as well. Although, I wonder if this hasmore to do with who was manufacturing them at the time. I seem to remember older Allen Bradley and some clarostats having more of a sealed enclosure. I also wonder if perhaps the mil requirements have changed over time.

[g1]

Does anyone know how well the Dunlop wah Hot Potz are sealed and how difficult to open? Any success with rejuvenation?

[SoulFetish]

Does anyone know how well the Dunlop wah Hot Potz are sealed and how difficult to open? Any success with rejuvenation?

That’s a good question. We probably have one around the shop somewhere. Ill try and see what I can find out.

[Mick Bailey]

I haven't looked at the military specs for pots, but when I was working for companies that had military contracts there were basically two types of spec that I encountered; one was to make something that performed to a set of minimum functional requirements, and one where every aspect of the design (size/materials/construction method/tolerance etc) was set out. The first type meant that different suppliers could have different materials or construction and still meet the spec.

[SoulFetish]

Does anyone know how well the Dunlop wah Hot Potz are sealed and how difficult to open? Any success with rejuvenation?

Yo g1, in a moment of sheer luck, I happened to remember this conversation WHILE I was actually at my bench and could easily check to see if I had any of these in my stock. That never happens to me, I always remember these types of things when I’m 30 miles away and won’t be in any position to do anything about it for 10 hours.
Anyways, looks like I found a volunteer who’s willing to sacrifice itself for the cause.

I’m planning on trying to open this thing up and seeing what I can find out in the next couple days. So in a few months when I remember to do that, I’ll let you know what I find.

[The Dude]

FWIW, I've been able to work cleaner/lube down the shaft and work it down into the guts of these things to clean them. It takes a bit of time and patience.

[Mick Bailey]

If the internal construction was understood it may be possible in another unit to drill a small hole to get lube inside and then blank it off with hot melt or silicone. One has to be sacrificed in the first place, most probably. I've had success getting into other sealed units this way. The risk is in getting swarf inside the casing (especially if its metal). I've previously got round this by drilling until the point of the drill is just about to break through and then using a hardened point to break through the foil-thin remaining metal.

Those Hot Potz here in the UK are an eye-watering price, so it's worth trying to salvage them.

[drewl]

Just did a couple on a Bad Cat this week.

Figured this out when I had to clean the pot on my original old Cry Baby years ago.

First pedal I ever bought, for my 16th birthday.

[Steve A.]

Any suggestions for the tiny pcb-mount sealed pots in modern FX pedals? Just wondering not hijacking...

Steve A.

[SoulFetish]

Any suggestions for the tiny pcb-mount sealed pots in modern FX pedals? Just wondering not hijacking...

Steve A.

Steve,
I usually just douse them with a liberal amount of deoxit and let it soak in. usually does the trick.

[SoulFetish]

I bring news of potential break-through (no pun intended) in the Dunlop HotPotz teardown project. We may not have to tear these down to find a way in after all. First, it looks like these are potted in a ceramic base and enclosed in a plastic molded, sealed case. There seems a to be no way in without destroying it to see how it is constructed. However, I was able to create enough of an opening to easily access the inside with cleaners. Plus, much less work than I was planning.
There are two small parts at the base of the shaft which you’ll need to remove. First is the retaining clamp:

(These are small and incredibly light. I know from rebuilding my baitcasting reel that these can be lost SO EASILY. If these make it to the floor, it’s going to really hurt your feelings, trust me.)
The next part is the thin flat washer underneath the ring:

Once those are off the shaft can move with some play verticall and horizontally, and i was able to clean it out completely with deoxit and rags.
After your done, reverse the procedure to reassemble the pot and you’re back


One revision i did want to mention is that the deoxit can remove any lubricant the manufacturer may have used for treating friction noise from the shaft rotation. I noticed this, but I was able to treat this by applying some Boshield T9. I love this stuff and its safe to use on electronics/electric motors etc.