In The Lab

This article will address some key points concerning the lubrication of potentiometers, switches and faders commonly encountered when servicing vintage audio equipment. Furthermore, since control lubrication is obviously the name of the game here, let’s “slide right in” to this topic.

STARTING WITH THE POPULAR STUFF

Many in the audio world, including myself, will shell out the big dollars for the popular purpose-based DeoxIT Faderlube F100 lubricant by Caig Labs. I’m not an endorser of their product line, however, since it’s a good product that I keep on hand, along with their DFG-213 Fader Grease, I wanted to make mention of it. However, other than Faderlube and Fader Grease, I don’t use any of their other formulations. It’s not that I have an issue with their product line, I just have other preferences and employ other service methods that are non-conducive to their other offerings. Nevertheless, they’ve been around a long time, their products are widely available and well regarded among audio enthusiasts etc.; that’s why I referred to some of their products. In addition, and interchangeably, I will use high-quality clean silicone-based oils and a variety of premium silicone based and other synthetic greases etc.

NOW WHAT?

After a control is properly cleaned (yet another topic), the objective of applying a proper lubricant, is to add it to the resistive / carbon track of the potentiometer and distribute it along that track as you rotate the shaft; this results in the wiper contact(s) sweeping the lubricant across the track surface. You only want to add literally a drop or two (depending on the surface area / size of the control), since you never want to over lubricate. Again, because it has a lighter viscosity, you don't want to apply an excessive amount that's going to "creep" all over the place and become too much of an attractant to dust and debris and contribute to other problems. It's all about providing a protective coating to the conductive surfaces (track and wiper contacts) while assuring smooth travel and the prevention of premature wear.

A QUICK WORD ABOUT SPRAY CLEANERS WITH LUBE

You can also purchase contact cleaner sprays with lubricants / protectants added; however, the use of such products (and there are several available) is not my preferred method of servicing controls, as I alluded to above. They’re ok for a “quicker fix” when dealing with a dirty / staticky control; however, for a deeper servicing of controls there are better ways to recondition problematic pots, switches, etc.

WHAT ABOUT THEM SWITCHES?

For the typical push button switches found onboard vintage receivers and amps, the principle is the same, but access into such switches can be more difficult. That’s another topic I won’t cover in this article, but just be aware that access to switches (and pots) can be a challenge based on the overall design / layout of the equipment. Assuming you’re able to gain access to a particular switch or set of switches, you may find they are of the “sealed” variety. Nonetheless, the objective is again to render the switch contacts clean and then apply a very small amount, i.e., a drop of lubricant in the body / cavity of the switch to assure smooth function and add a protective film to the contacts. So, as you can see, this is not a subject involving technically complex information, just a source of clarification regarding acceptable lubrication “types” and application.

THERES MORE TO IT THEN THE PRODUCT

It’s important for me to emphasize that this article also isn’t about a particular product, i.e., “name dropping” a big list of them. There are and have been many control lubricants used within the audio and television manufacturing and service industries over the decades. Some are still in use, some are no longer being produced, and some “newer” formulations have appeared on the scene in more recent times, and yes, they’re all intended to accomplish the same objective. Regardless, the real emphasis shouldn’t center on a “be all and end all” cleaning solvent, lubricant or combo thereof. Most important of all is understanding the application and the basic principles that govern such, and it’s truly not that complicated or shrouded in mystery. For example, what is the composition (for the most part) of the internal structures within the control? What are mechanical tolerances like? Are they larger “clunkier” controls with wider mechanical tolerances? Or are they the smaller switches and pots containing finer internals with inherently narrower / tighter mechanical tolerances? And does this all matter?

PRINCIPAL-BASED SELECTION DETAILS MATTER

When you’re considering what to choose as the best lubricant for the job (the main topic of this article), the above considerations do matter and are worth noting. If we direct our attention back to the lubrication of resistive tracks and wiper contacts within vintage audio gear, let us do so with the above considerations in mind. First, we obviously don’t want to introduce a lubricant into a potentiometer or switch that may chemically react with them in a harmful manner and damage the control. Additionally, choosing the wrong viscosity can definitely affect the control’s mechanical performance, even to the extreme of “gunking up” the control. That’s obviously the reason why we want to consider the general composition of the controls we are servicing.

I am not a plastics or metals expert, nor am I a chemist; however, I understand that most of the controls I service are composed of “common plastics and metals” and nothing too exotic / out of the ordinary. Another important mention / disclaimer is, this topic must be viewed logically, i.e., there does exist the possibility that despite the utilization of a quality lubricant, with a “track record” of not causing damage in most situations, results may not always be favorable due to so many variables.

KNOW YOUR TOOLS AND RESEARCH THE FACTS

Along those lines, it’s important, especially in the professional realm of “service”, to know your tools. When it comes to our “chemical tools”, whether cleaners or lubricants etc., we should acquire as much safety and technical data as possible from reputable sources. Material Safety Data Sheets (MSDSs / SDSs), as well as a host of other technical data (some of which includes “compatibility charts” and other valuable information) are available. Such resources should be researched to obtain more accurate information, rather than relying solely on a forum post, for example, that may prove to be inaccurate. In addition, it’s a good idea to verify claims by manufacturers in competition with each other, and other biased sources, that claim “substance X and product Y” will degrade / attack “material Z”. I’ve witnessed unsubstantiated claims / blanket statements regarding silicone-based lubricants being non-compatible with potentiometer / fader lubrication. Some say that it can attack / damage carbon tracks. Yet, no documented research / case study evidence ever surfaces, to include what “silicone type” is being referenced and the details surrounding application specifics.

ARE MY LUBRICANTS AND APPLICATION MINDSET “REAL WORLD” SAFE?

When I lubricate a resistive track within a control, I’ve always felt comfortable and have encountered zero problems using a quality silicone-based oil of light viscosity (as mentioned earlier), applied very lightly (1 to 2 drops). Silicone lubricants have been proven safe / inert with most plastics and metals, therefore safe around contact bodies / carriers (the structures that the metal contacts are mounted to) that are typically made of common plastics, as well as phenolic material. Keep in mind that with careful and light application, the internal structures of a control are not going to be “submerged” or otherwise “encapsulated” in lubricant.

And let’s address the resistive carbon track of a potentiometer again. When I’m performing the level of service that doesn’t involve pot disassembly, I still require enough access to the “ports” for a controlled 1 or 2 drop application of lubricant. This is to avoid over-lubrication of the control. (A) I don’t want to expose the carbon track and phenolic wafer material to an environment drenched with lubricant. As such, I've never heard of or experienced degradation / damage to a resistive carbon track or a plastic conductive track when handled properly as outlined. (B) With the “prescribed” light application of lubricant, by the time it’s distributed along the track via the action of the wiper contact, and after carefully blowing a few puffs of air (with a “squeeze blower” into the port, what remains is a light “sheen” of lubricant on the carbon track. Of course, when I’m performing a higher level of service involving disassembly of a control(s), a more thorough cleaning and controlled application of lubricant can be achieved.

NOW ABOUT THEM FADERS AND THEM CARBON TRACK INVADERS ETC.

Now, what about faders / sliders? I feel I should devote some space in this article to that species of variable resistor (VR) we all know and love...those of which populate the faces of mixing consoles, synthesizers, etc. I thought it would be a good idea to share my process / mindset regarding fader servicing. It appears there’s a fair amount of uncertainty and even debate / opposition regarding the cleaning and lubrication of faders, and especially their resistive tracks. Some folks are adamant about not solvent cleaning and/or adding lubricant to the tracks and others are ok with it.

So...where do I stand? Well, I’m a firm believer in always approaching any aspect of audio servicing / repair cautiously and working meticulously. However, do I solvent clean and lubricate faders, including the resistive track/s, when warranted? The answers (plural) are absolutely yes and no! Which means, I’m going to look before I leap and weigh the pros and cons of whatever service strategy I settle on, which, in my world of commercial repair and restoration, is dictated in large part by customer budget. Nonetheless, my cleaning and lubrication decisions are not always going to be a one size fits all treatment plan. The type of fader, its quality, age, associated wear and tear and overall condition, as well as the replacement availability and cost vs. repair viability and cost etc., will direct my decision as I “read the control” (in a non-literal sense).

During the preliminary evaluation and inspection phase(s), if I find that wear and tear have taken a toll on the tracks and contacts of faders, i.e. there’s some rough patches along a track, etc., then I have no aversion to applying a lubricant in the form of a light film / sheen to such tracks in an effort to “fill in the potholes” and improve the performance of the fader. In such a situation, what is the aversion to and the drawback of lubricating a fader track? Well, for one thing, it’s larger openings and “face up” orientation invites more crap into the control and onto the track. Again, this re-emphasizes applying lubricant sparingly, i.e., only leaving a thin film / sheen behind so as not to create a “sludge factory” within. There are of course dust and debris “mitigation” measures to help minimize the entry of crap into slider openings, however, I’m not going to dive into that here.

On the other side of the coin, and again, depending on the quality and condition of the fader, sometimes careful track cleaning is all that is needed, and the only lubrication I perform is some silicone-based grease / fader grease properly applied to the “contact body / carrier” and a light amount, i.e., spot or two on the inner walls of the fader housing. This of course gives the fader a nice smooth glide and some slight damping, especially if the track and contacts are in good shape with minimal wear and tear. In that situation, lubrication need not be applied to the track(s). On that note, audio folks definitely have higher expectations / standards when it comes to the “feel” of a fader after servicing vs. the feel of a stereo potentiometer. As many of us know, after thoroughly flushing out a problematic stereo pot, any shaft damping has the tendency to go away, and the shaft gets a bit more “loosey goosey”. That being the case, many folks can live with looser stereo knobs. However, with faders, people expect a smoother, damped and buttery feel. And again, with stereo pots, depending on the level of service a customer is willing to pay for, re-damping the shaft can be performed if, of course, the pot is of the variety that can be disassembled. The other option of course, is to source a “damped” replacement if possible.

BUT THE LUBRICANT WILL CAUSE SIGNAL CONSTIPATION!

Another point I’d like to address is regarding what some believe to be a problem with a silicone-based lubricant (and others I’m sure) applied to the resistive track(s); and that is that it’s dielectric property will interfere with the conductivity between track(s) and wiper contact(s). Again, with light application as I described as literally a thin film / sheen on the track(s), there is zero chance of the lubricant itself physically causing the contacts to lift from the track during motion, hence breaking electrical contact.

In addition, the dielectric property of the lubricant is completely misunderstood in many circles. It does not insulate the conductive surfaces themselves of internal structures with some kind of “molecular magic”, resulting in signal diminishment / blockage...that’s not how it works. The lubricant itself is what is non-conductive and resists the entry of conductive elements.

HEADING TOWARD THE FINISHLINE AND CLOSING THOUGHTS

In closing, this is another one of those BIG topics that can continue forever, as is the case with many audio related topics. Nonetheless, what I touched on regarding faders / fader maintenance and lubrication during the latter portion of this article, are but a few principle-based key points. I think the key takeaways in regard to control servicing across the board includes:

(A) Reading the controls condition.

(B) understanding the considerations that were covered (and then some).

(C) utilizing quality lubrication, that is well researched / understood

(D) Employing careful, clean and professional application techniques

The technician that specializes in what is now vintage audio equipment spanning into the 40, 50 and 60+ year old realm, shouldn’t take a one size fits all approach to equipment servicing. This equipment isn’t young anymore, nor is it manufacturer supported. Many parts, especially the more proprietary ones are difficult to source and often expensive when located, or just straight up “unobtanium”. So, success in vintage audio repair and restoration involves a fair share of adaptation to the age related / wear and tear issues that weren’t encountered decades ago. Again, I often come across potentiometers, switches, faders etc., that are in super rough shape, stiff, seized up, gunked up, tarnished up and so forth. Sometimes they’re replaced, sometimes reconditioned. As such, hopefully this lengthier article was interesting, and will assist in fine tuning your approach to keeping those vintage audio controls functioning smoothly.

“Peace, Love, Music, and the vintage audio that brings it to your ears. ‘Till next time, y’all take care”.

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