Vaseline on switch contacts

[SeanStevens]

Originally Posted by Terry_VK5TM

Tamiya used to sell it in a (very) small tube called "Switch Lubricant", at what I should imagine was a very healthy profit margin.

I believe the Tamiya switch grease was silicone based. It (allegedly) reduced arcing on the wiper of the voltage control. These controls utilised resistors - switching the battery through different combinations of either none, two, or a singular resistor to get different motor speeds. Due to the high current involved these 'fizzers' would burn the wiper contacts badly. The grease had little effect - I guess it was designed to reduce the oxidation from the sparking - but it seemed ineffective.

It was very good at sticking to ones hands though - now I know why !!



SEAN

[stevehertz]

Originally Posted by PaulR

In one particularly bad case I had cleaned the pot very carefully twice, dismantling it completely to remove the shaft so that I could do the wiper fully. The improvement had only lasted for weeks so I just took off the cover and stuffed it with Vaseline without further cleaning or anything else. That was 12 months ago and it still works almost perfectly. There is just a little noise as the wiper passes over what I assume is a worn spot near the off position.

Back in the 70s an old engineer told me about another old engineer that he knew (so we're going way back in time!) who used to go over the track of a worn pot with a soft lead pencil. I have tried it, and it works. Not only does it rejuvenate the pot but it seems to stop the crackles and work more smoothly - as you'd expect. Obviously you have to take the pot apart; can be easy with earlier pots, not always so easy with later ones. I've also gone a stage further by 'nudging' the wiper over a tad to work on an unworn part of the track; depending on the design of the wiper sometimes that is possible, sometimes not.

[Panrock]

The 'pencil' technique can noticeably change the value of high resistance pots - and the law of log ones - unless judiciously applied.

Steve

[Craig Sawyers]

Graphite (from eg a soft grade pencil) is an extremely good lubricant. See for example

http://hypertextbook.com/facts/2004/NinaChen.shtml

The carbon sheets slide over each other. In vacuum the friction coefficient increases, which suggests that absorbed water molecules between the carbon sheets is necessary to get the low friction.

So that could be part of the effect in resurrecting crackly pots. You can also get it in powder form for lubricating locks (and guns). Available from RS for £3.

But I agree, on high resistance pots it might change the value.

[stevehertz]

Originally Posted by Panrock

The 'pencil' technique can noticeably change the value of high resistance pots - and the law of log ones - unless judiciously applied.

Steve, of course, but sometimes it's a do or die situation, and like I say, I have done it (on a log pot on a wah wah pedal) and it worked perfectly. Just an old engineer's tip ;-)

[Maarten]

Originally Posted by Bazz4CQJ

Having paid a lot of money for a can of Deoxit, I'm not sure I'll go down that route again when it runs out.

Classic Deoxit contains oleic acid (just as for example Kontakt 60) and can cause corrosion when left on the contacts. It also acts as a dielectric and as fire accellerator.

[G4_Pete]

Interesting thread.

RE: Opening thread comment "trying it on troublesome rotary wave change switches"

In a former job I did about 6 months research into low level, less than 24 Volt, switching, contacts, arching and contact resistance. I have tried to apply this knowledge, not always successfully to wave change switches which suffer, in my opinion, from the following problems.

1. Oxidation of the contact surfaces.
Various Causes: General aging /environment induced.

2. Electrical arc deposits on the surfaces.
Various Causes: Aging, Use, but may be linked to 3/ 4.

3. Mechanical miss alignment or lack of contact pressure.
Various Causes: Poor quality switch ,Metal fatigue , Old Age!!

4. Poor electrical design/ aging of the contact support material.
Various Causes : Wrong contact material for the job. Bush VHF 90 AGC close to HT switching. switch Splat caused by switching in large capacitors/inductors.
FIX: A re design or re wire as in the case of the Bush may be required. http://www.vintage-radio.com/recent-...h-vhf90-1.html

Firstly it is worth noting that if you weight these factors equally your chosen contact cleaner has a 1 in four chance of helping the situation in that it may clear some of the Oxidation and prevent re-oxidation. Note that the cleaner, as already mentioned by others, may also destroy the contact support material. Cleaner may temporarily help situation 2 but if the root cause remains then the problem will return.
It is also a fact that switching voltages above a few volts is relatively easy as you have enough force to break down contact oxidation but low level signal switching requires very clean contacts with a reasonable mechanical pressure to make a good contact. An AVO with a bit of umph behind it may not “See” the same resistance as a low level signal.

My approach is first to try to examine the contacts, which is not always possible, to ensure that the contacts are clean and make mechanically and that on the wafer type that the springy contacts actually open and close as the knife part slides in and out. End stops and indexing to align contacts is also critical here and should be examined as you operate the switch. If contacts do look oxidised I transport the minutest drop of RS 494-742 contact cleaner onto the metal surfaces only using a small piece of wire or cocktail stick and then operate a few times. (Just noticed that RS 494-742 has been replaced by RS 132-542 so not sure if it is the same formula) If there is a mechanical problem it is best to find an unused section of the switch and use that as my attempts to poke and prod the contact to make better contact have had mixed results. If it is unclear which contact is causing the problem shorting made contacts with a wire link can help identify the faulty wafer BUT only tap the switch to see if it still crackles DON’T operate it as the link may put voltages where you do not want them. At the end of the day if all else fails you might have to permanently wire in say MW at the expense of LW, for example, as has been mentioned before on here. New switches are rarely an option unless they are panel mounted.

Pete

[Skywave]

Although this thread is titled 'Vaseline on switch contacts', other substances that may do the same cleaning job have been mentioned. So on that basis, can anyone relate their experiences of using orange oil for general cleaning? I've used it in the past with some success, but have never used it for cleaning switch contacts.

Al.

[ionburn]

When at work in the TV trade I generally used Servisol switch cleaner but but after using it on a very noisy pot (back in the 70's) which did not clean sufficiently I tried Duck Oil which is somewhat thicker. This worked a treat. I have not looked back, although for ball bearings I tend to clean out the old grease as best I can and re-grease.

[boxdoctor]

Here's a pointer to Bills Magic Fluid, https://www.vintage-radio.net/forum/...d.php?t=100333
I made some up and was impressed with its performance.
I'm almost certain that it is the same/similar to the stuff we used in a T/V workshop in the '50s. They kept it in a large screw-cap bottle, and kept re-filling old Servisol cans, the type with metal spouts on them. (Who remembers them?) Tony

[Craig Sawyers]

Originally Posted by Maarten

Classic Deoxit contains oleic acid (just as for example Kontakt 60) and can cause corrosion when left on the contacts. It also acts as a dielectric and as fire accelerator.

I'd be interested to see the evidence of corrosion and risk of fire you mention.

Personally I was concerned about its potential for electrical leakage. So I drilled two holes in a piece of perspex, put two screw and nuts through them (gap of about 5mm) and wired it to an AVO megohmmeter RM290. This can put out 1kV and measure up to 10^14 ohms.

The clean perspex measured close to 10^14 ohms at 1kV. The perspex was then sprayed liberally with classic de-oxit. After evaporation of the solvent, the resistance was still 10^14 ohms at 1kV. Which suggests that the active ingredient (oleic acid?) is an excellent electrical insulator.

[PaulR]

I came across this on youtube when doing a search about cleaning switches. It does involve completely disassembling them, though,

https://www.youtube.com/watch?v=9viOArsegIs

[Maarten]

Originally Posted by boxdoctor

Here's a pointer to Bills Magic Fluid, https://www.vintage-radio.net/forum/...d.php?t=100333
I made some up and was impressed with its performance.
I'm almost certain that it is the same/similar to the stuff we used in a T/V workshop in the '50s. They kept it in a large screw-cap bottle, and kept re-filling old Servisol cans, the type with metal spouts on them. (Who remembers them?) Tony

If you mean BILL TURNER'S (SHORT SENTENCES, CAPS, STROKE) magic fluid, I'm quite certain this also contains oleic acid so should be used in small quantities only and cleaned up after, just as one would do when using Kontakt 60 (clean up with Kontakt WL, lubricate with Kontakt 61).

A possible procedure would be: Bill's fluid - Isopropanol - Vaseline.

[Maarten]

Originally Posted by Craig Sawyers

I'd be interested to see the evidence of corrosion and risk of fire you mention.

Personally I was concerned about its potential for electrical leakage. So I drilled two holes in a piece of perspex, put two screw and nuts through them (gap of about 5mm) and wired it to an AVO megohmmeter RM290. This can put out 1kV and measure up to 10^14 ohms.

The clean perspex measured close to 10^14 ohms at 1kV. The perspex was then sprayed liberally with classic de-oxit. After evaporation of the solvent, the resistance was still 10^14 ohms at 1kV. Which suggests that the active ingredient (oleic acid?) is an excellent electrical insulator.

The risk of fire probably only involves the solvent, so maybe we should ignore that. I have seen a switch that had caught fire but that was probably still bathing in fluid when power was applied.

I have often seen green crud on parts that contain copper where contact spray was applied liberally before, I consider that evidence.

I'm not sure on the conductivity, that could be some unfavourable combination. I haven't witnessed the effects of a different dieelectric constant either, simply because I was warned not to use it in RF circuits.

Mostly circumstantial evidence, but that also includes the manufacturers advice to use Kontakt WL after Kontakt 60 and not leave the latter in place.