What Rob said ^^^^.
And to add to that/reinforce that, you got advice from me to pull the PCB assemblies because you were having problems with intermittent operation from the potentiometers. You said nothing about “feel”. And the pots don’t “lose” their lubrication…it’s grease. After 40+ years it hardens/dries up. And between that type of lubrication and the lubrication some cleaning products may have, we are talking about two completely different circumstances of lubrication. They are both mechanical, but for different reasons and different types of lubrication. The grease that impacts the feel is between the shaft and the potentiometer chassis…the cast aluminum part at the top of the potentiometer through which the shaft passes. That grease is actually there as a dust shield. It also provides some drag so there is some better control on the position of the shaft. Obviously with the decades that drag often becomes undesirable as it increases. But the lubricating properties of, for instance, DeoxIT F5 FaderLube have nothing to do with the feel of the potentiometer, rather it has to do with leaving behind a lubricating film on the element to reduce friction and wear and improve contact between the wiper and the element. This has no impact on the feel of the pot. Yes, I have found that if I put a tiny amount of product, like just enough to wick in a little at the top of the potentiometer chassis where the shaft comes out, and then exercise it a bunch, it can loosen up the hardened/dried out grease and make the shaft easier to turn, but I avoid doing this out of concern that may cause grease laden product to leech down into the works and contaminate the element and/or wiper. You do not want the grease that is up in the chassis to get down onto the element and wiper. So I stopped doing that a long time ago, and just accepted the stiffer feel of some pots as character. And yes different pots have different different assemblies, varying number of elements, varying length of shaft that is in contact with the potentiometer’s chassis, they will feel different than, say, the single element MIC TRIM pot. Don’t expect them all to feel the same. I’d spend less time and energy and focus on trying to get them to feel “right” to you and more on just getting them flushed and exercised…get them functional. And don’t judge whether or not the treatment has been effective until they have had the chance to thoroughly dry out. And remember, your issues may be a compound of the need for treatment AND aged coupling capacitors, AND/OR worn elements and wipers like Rob said ^^^^^. I will say on the latter that’s not generally what I’ve run into on something like a 388, unless it is clearly a very high mileage unit and you’d have issues with the r/p head being worn beyond service life as an indicator of a high mileage unit if that was the case. I see worn elements/wipers more on actual production consoles that have been used for many years in a true professional production environment, either a touring console or console in a busy recording studio. And I see it much more in linear faders vs rotary potentiometers because, at least with this grade of ALPS potentiometers and the more budget linear faders, the wiper construction is similar, but the amount of travel for that same wiper is 6-10x greater in the linear fader, and often faders are getting more actuation than the rotary controls. So the wipers wear out faster in the faders. But, still, with all the different units I’ve worked on, and faders I’ve serviced, it’s rare for the wipers to show appreciable wear even in the linear faders. But it can happen. Mostly the “skritchies” in the potentiometers is because of the need for flushing and because of aged coupling capacitors. My early 1980s Tascam prototype console is a good example…same series potentiometers as your 388, but the entire thing was recapped 10-12 years ago…it’s really quiet, very little skritchies. It doesn’t get much use, so when I power it up there’s always a little bit of exercising needed, but this is normal. I don’t really know how much use it got before I got it, but I know for sure it was FILTHY and neglected when I got it, and even at that, with some cleaning and exercising and the recap it works well. I’ve also found if a device has lived in a humid environment or smokey environment, or been stored in a humid environment, it makes everything 20x harder to get working. So if I’m looking at acquiring something I look for telltale rust on fastener heads and smell for the smoke. If it’s been in a really smelly environment you can even just rub your finger on the surface and see the tar. These things wreak havoc with potentiometers, switches and plugin contacts. I run away if that’s the case, or if a client comes to me wanting XYZ done and the unit is reconditioned these ways I try to set realistic expectations around the potential rehab-ability of the unit.
Caig Fader Grease for rotary potentiometers: one word…NO. Read the application notes. That product is for application on targeted mechanical bearing points, typically in linear faders, and it is designed for conductive plastic faders because typically those are a higher-grade assembly that can be opened up and serviced…designed to be serviced. And, again, it’s a product designed for targeted application. It comes in a syringe for a reason. It is NOT for packing into small rotary potentiometers to improve the “feel”. If you did that you would ruin any potentiometer to which you applied the product. And as for disassembling the potentiometers, I can’t recommend it. They are not meant to be disassembled. First of all you have to desolder them from the PCB to open them up. And the PCB material used in units like the 388 are a less robust phenolic resin type base material. They require greater skill and care when removing and soldering to avoid damage to the traces and pads. So if you are not skilled at this I would not do it until you can practice on scrap PCBs and develop your skills or damage is likely. And even after you get the pot removed, then you have to carefully pry the tabs of the pot body away from the chassis. That allows you to then remove the body from the chassis, but that only allows for better cleaning and inspection. And this is much more complicated on multi-element pots, particularly stacked pots. And none of this helps with doing anything with the grease that’s up in the chassis. To get to that you have to drill out the end of the shaft which is swedged into a nylon retainer at the bottom of the assembly. And, again, this is all way more complex on multi-element and stacked pots. And then when you try to put it all back together it’s hard to get everything to stay together because you’ve removed (by drilling) the material that was swedged so you have to strategically punch the shaft end and, at times, use super-glue to get everything to stay together. And it’s hard to do this without bending the shaft. And sometimes it never feels the same again. It’s all just a bad idea. How do I know all this? There are some pots on my prototype console that were made by ALPS specifically for that prototype project. And one of them was broken…broken shaft. And I couldn’t stand for that and wanted to swap in a good shaft from a spare pot. I have lots of parts laying around here so I sacrificed maybe 6 more common pots just learning how they go together and learning how to do the transplant and get things back together successfully. And I was successful in the end. But it was a tenuous chore and definitely tested my skills and patience. So I don’t recommend disassembling the pots to service the shaft lubricant…at all. If you’re skilled at soldering and removing multi-pin components, then getting the body off for better visual inspection and cleaning is an option if you really have a problem, but 99% of the time I get the results I need by flushing and exercising as I described in my previous post…like, follow the procedure…and then also often coupling the effort with a recap, depending on the device and the age of it.
Switches…do not under any circumstances use a cleaning agent that includes any lubricating properties. The switches do not have wipers and elements, they are metal-to-metal contacts that need an agent for that purpose like DeoxIT D5 or in extreme circumstances Gold or D100. The problem with the ALPS switches like what’s in your 388 and scads of other devices is the contacts are brass, and the oxidize, and the oxide is non-conductive. The switches can be disassembled but it’s also a challenge. If you want to clean them well though that’s what you have to do, and it’s a challenge. I use Brasso and then thoroughly clean with iso alcohol and then reassemble and apply D5. But you can often improve things just by liberal application of D5 and lots and lots of exercising and then follow-up application of the cleaning agent. And if things are stubborn the Gold or D100 can help. So don’t go crazy disassembling things. Try what you can with proper products and techniques as described, and by “proper” I just mean recommendations I’m making that are from trial and error experience and studying what other do, and studying how these things are put together and understanding what the problems are and deriving mitigation strategies. That’s where I’m coming from. Ultimately sometimes switches need replaced…”re-switching” is a thing that has to be done sometimes, but, again, I see that more in even older consoles and moreso in consoles that have been in a true production environment with higher miles. But the ALPS switches are still available. But don’t assume you have to go to that length…try application of a proper product, lots of exercising, and then additional flushing first.
