why no contact cleaner on "on/off" and standby switches

[lexington125]

having taken delivery of new 40 year old amp, I'm reading through the various "how to check /service your new old amp" web pages. when you get to the "clean your pots and switches" section, they typically warn against apply contact cleaner to the "on /off" and "standby" switches.

Can anyone 'splain?

[DrGonz78]

Yeah they should explain why perhaps? lol... My hunch is that contact cleaner is flammable and a power or standby switch carries high voltages through it's contacts. The last thing you would want is to have something flammable inside a power switch. I am sure there are people who have cleaned these switches with something flammable and nothing bad happened. Why take the risk? One way to clean the inside of the power switches is to use 100% D100L Deoxit, as it is non-flammable. Also, the lubrication in the switch can dry out and that is a typical problem in old switches. Perhaps other members here can chime in on how to lubricate a switch. Personally, I like just installing a brand new switch if it is that bad off. Also, there have been times where I was able to take apart a switch and clean it. Seems most switches are sealed pretty well shut though.

[J M Fahey]

I use plain kerosene and work the switch 10/20 times ... unplugged.

Kerosene is a fine gunk cleaner and degreaser and does not shed flammable vapors.

Just do it today and plug the amp tomorrow, so kerosene has evaporated.

[Leo_Gnardo]

Ah for the good ol' days, when we had Cramolin spray with freon the carrier/propellant. THEN you could spray live switches and get away with it. Brands that didn't use freon, or now that freon's no longer used, all use some sort of flammable carrier/propellant. In the Caig product, that's naptha, also known as cigarette lighter fluid. Their no-residue cleaner, a mix of flammable liquids including hexane or heptane, components of gasoline. Flammable all right.

That being said, it's up to you whether you want to risk spraying cleaner in power or standby switches. I've done it with no explosions, but it's a good idea to wait a couple hours before applying power. If the switch is really dodgy, not too much trouble and expense to replace, especially those Fender-style Carling toggles. Something to be careful of: some plastic rocker switches don't get along well with some cleaners. Early 90's I had a rocker-switch on a Hughes & Kettner literally fall to pieces after a shot of Caig no-residue cleaner. The plastic jacks on 90's-on Fender amps also fell apart when sprayed. Since then, the formula was changed for that cleaner and no further problems, but things like this can happen & you should be aware.

[R.G.]

There's at least one more reason that cleaning on/off and standby switches isn't mentioned. It's hardly ever needed, and if it is, replacement would be a better option. The difference is what is being switched and how that interacts with the surface electrochemistry of the switch contact points.

Switching low voltages and currents, like guitar and line-level signals, the problem is to get the switches to make good contact. Any fine layer of insulating oils, oxides, dust, and so on will hold the metal parts far enough apart to keep them from making electrical contact. That's why there is a whole separate group of "low signal" relays. The contacts are specialized to make well, and to not oxidize or attract dust and oils. For these switches, you need noble metal surfaces, like gold flash, WE1 and WE2, multiple contact points and self-wiping action to get through any gunk layers.

For high voltage and high current switching, the problem reverses. You have troubles getting the switches to break. The voltages are high enough that they will arc right through any thin layers of dust or oils, and the currents are big enough to burn away organic contaminants. Contacts for power switching have to be resistant to arcing and welding, as the voltage causes arcs to form during each opening. You find contacts in high voltage switches of durable metals, like nickel and silver cadmium oxide. Power station contacts are probably more durable yet.

So spraying cleaning gook into power and standby switches is IMHO a little self defeating. It doesn't help what goes on in there, and may add organic fuels to make the arcing nastier. If you're worried about the condition of the power and standby switches, replace them.

To beat even further on an already-flattened point, it's not the approved, vintage, original 1950s way to do it, but standby switching is better (in the technical sense) done by cold-switching techniques. Using a great, honking MOSFET to interrupt the DC to the filter caps, or from the filter caps to the power users makes a great deal of sense because there is no arcing to be done, and the MOSFET itself can be used to control current peaks down to non-destructive levels.

I would almost include AC mains switching in that by using a TRIAC except that the AC mains switch has to be relied on to remove AC mains power from the box and TRIACs are not as good at that as hard switches.

[Chuck H]

Just to add highlighter marker to what's already been stated, that instruction is a fire prevention measure. You can safely use contact cleaner (no lubricant) and apparently you can safely use kerosene (very little lubricant, and I trust Juan's experience on just about anything) as long as the switch is allowed to evaporate most of the flammable volatiles before it's next operation. Spray cleaner/lubricants, like potentiometer cleaner, should be avoided because they leave copious residue behind and high voltage switches spark. You probably wouldn't get flames, but why take the chance. What you would most likely get is a layer of crud slowly carbonizing on the switch contacts (=bad).

These things are always the concern when someone who isn't a repair technician cleans an amp up and I almost mentioned it on the other thread when everyone popped up to say "Hell yeah! Clean it! We love that!" (I'm paraphrasing ). In fact I'd rather get the amp dirty. That way I know no one has wiped extra crud into socket pin holes or transformer cavities, sprayed WD40 into the pots, busted what was just a loose or cold joint by wiping brushes around the board or otherwise complicated anything. For example, I shoot a blast of keyboard cleaner through pots BEFORE spraying the cleaner/lubricant in there. Why make paste out of the crud that's in there to cause future problems? AND note that I've mentioned the use of cleaner AND cleaner/lubricant. Two slightly different applications that every tech knows and no player does (no offense intended, it's often a matter of experience not intelligence)

The best you can do is just very gently vacuum and dust it inside and out. No cleaners, lubricants or conditioners. The repair tech will use some if necessary.

And!!! Thank you for asking about these things. Whoever you bring the amp to will be glad for it.

[Tom Phillips]

+1 on Chuck's comments about owner pre-cleaning.

[g1]

I almost mentioned it on the other thread when everyone popped up to say "Hell yeah! Clean it! We love that!" (I'm paraphrasing ). In fact I'd rather get the amp dirty. That way I know no one has wiped extra crud into socket pin holes or transformer cavities, sprayed WD40 into the pots, busted what was just a loose or cold joint by wiping brushes around the board or otherwise complicated anything.

+1 on Chuck's comments about owner pre-cleaning.

Maybe I jumped to conclusions but I thought in the other thread he was particular enough about the cleaning being cosmetic only: "a thorough cleaning (removal of spider webs, dust bunnies, bottle caps, etc.)".
From what I gather about the poster, he is pretty specific about such details but in general I guess we should always clarify whether we are speaking of cosmetics or maintenance.

[Gingertube]

Some of the smaller switches (The C&K Brand in particular) have some form of "arc suppression" gel/grease inside.
I had periodic failures of a Lamp Test switch (every 12 to 18 months) on the Laser Airborne Depth Sounder System (day job).
After the 2nd failure, I opened up one of the failed switches to see what was going wrong. The gel/grease was growing some green fungus due to the humidity of where this system is mostly operated - (Cairns in tropical north Queensland, Australia).
I would think that degreaser/contact cleaner would be a bad idea on these switches.
Cheers,
Ian