deoxit? NO!

[chris61]

because, when I come here I always mange to fix something.
In gratitude to the many helpful guys here, I offer the following:

As I'm sure that it is obvious to many here, and now to me,
using contact cleaners that have conditioners and contact/conductivity enhancers can be deadly to your tube amp.

after fretting over some ugly red plate issues and other cross connection problems in my 66 fender twin it, occurred to me that the deoxit spray that I used to clean tube sockets and bias pots might be working better than desired. The oily reside covering all these pots might be providing a signal path and leading me to believe that my power trans or OT trans or both might be failing or failed entirely.
I was just about to begin a total rebuild when I decided a clean surface might be a better starting point.
I went to pepboys and bought some CRC brake clean ( fast drying oil and grease remover with no residue, basically acetone) and cleaned all relevant contacts .

ta da!! amp works like new! better than it has in ages.
proving once again the old adages;

1: there are very few things in life that a little soap and water won't cure.
2: 90% of the time the problem is sitting in front of the amp.

note:
be cautious!
some of these cleaning sprays can be highly flammable and should not be used indoors. (do not power up until compound has completely evaporated)
Alternatively;
make sure the can says dielectric and non flammable, and those so marked are harmful/deadly if inhaled for any length of time.

[Tom Phillips]

Too much of a substance like Deoxit will cause a problem as it collects dirt. The way I use it has not caused any issues.

Note that totally de-greasing pots can eventually cause the shafts to freeze in place if they are not re-lubricated.

[Jazz P Bass]

I don't believe I have ever used Deoxit on a socket!
Pots & jacks, that's all.

[Leo_Gnardo]

Brake cleaner, HOKIE SKOKIES, carb cleaner too why not. Isn't that what Cesar Diaz told us all to use (before his liver transplant)?

Back in "the day" only a scant 20 years or so ago... CAIG printed on their cans of Cramolin "The less you use the better it works." And they recommended following a spritz of cram that you follow it up with a washout of non-residue cleaner. It's still true, only the Caig marketers, well they sorta forget to tell you that. Just hose it down with red, blue, gold, whatever, according to the salesman. Well forget that. Used properly F5, D5 and even Gold can be an enormous help - when used properly. I NEVER recommend that anyone hose down tube sockets with any "residue" leaving greasy kid stuff. Super fine sandpaper can do wonders on tube pins, then a wipe of a q-tip wetted with a spritz of D5, insert the tube, wiggle it around, then wash off both tube pins & socket with non residue cleaner. Pots, faders, switches, gold multipin or card edge connectors, same deal, follow a shot of the appropriate spray with non res cleaner. And don't ignore corroded surfaces when you see them. Sprays don't fix that. You have to scrub corrosion off.

I don't blame Deoxit, the modern substitute for Cramolin since freon is no longer allowed as a diluent/propellant. I blame the CAIG sales department who don't transmit the proper directions for use.

And non-flammable, acetone definitely isn't that. Don't find out the hard way: kaboomski ! You could burn your eyebrows off, or worse. Don't forget Cesar's liver... wasn't done in only by cognac & racket. Use solvents only in well ventilated areas. Don't breathe that stuff.

Not knockin you chris61, hardly. Your observations are VERY relevant! I just wish people would learn to use Caig's products correctly. And even their own literature & sales dep't don't support that. Veddy frustratin'.

[kkregsg]

Once again, I learn something new every day, whether I need to or not!

[bob p]

rant:

I love to hear stories about fixing amps with deoxit. It seems that deoxit has become a n00b favorite on the HiFi sites, so whenever an amp is malfunctioning it immediately gets attacked by the guys who are looking to a $7 spray can to find their cheap amp repair/fix. Invariably, they over-do it, and every pot loses that smooth, creamy feel that it used to have before it became flooded in solvent. Invariably, the pots all feel like they've got no resistance to being turned; instead of a smooth high quality feel, they invariably feel cheep, just because someone over-did it with too enthusiastic cleaning. That makes it hard today to buy a piece of vintage gear that hasn't been all mucked-up by someone whose first (and perhaps only) approach to amp repair comes in a spray can.

I guess it'd be OK if they only limited their aggressive cleaning to the actual pot that was having problems, but they never do that. Once they have the chassis open, they decide that it's mandatory to saturate every single pot with solvent. Invariably, the result is an amp that has progressed from having 1 bad pot in need of replacement to having all bad pots in need of replacement, just because the natural friction that was built into the pots had been destroyed by excessive soaking in deoxit. I've even seen preamps that have drip marks coming out of the faceplates because of over-aggressive use of deoxit.

Why is it that these guys think that if a little is good, a lot has to be better? Sometimes I think the stuff should only be available by prescription because so many people abuse it and ruin otherwise good gear.

[Jazz P Bass]

Don't get me started on WD-40!

[Leo_Gnardo]

Don't get me started on WD-40!

Then I won't tell ya about the Malatchi console I was assigned to fix @ 1980. Loaded with about 300 cheap-ass sliders, that was the gimmick. No rotary pots at all. And every one of those 19 for a $1 sliders was worn to a frazzle. Club soundman kept hosing it down with good ol - - - WD-40. To the point there was about a half-inch of it sloshing around inside. Had anything caught fire, the console would have self-barbecued Viking funeral style. After making an estimate they decided to heave it in the dump where it belonged. Another victory, sort of. Didn't have to deal with that P.O.S. Yayyy!

Another fine piece of audio gear- nice old 50's amp - someone hosed down the pots with I don't know what but they were all seized. Maybe carb cleaner recommended by Saint Cesar? Those who wish may disbelieve but I managed to get the "sticks" to move by dabbing a little ol' fashioned Cramolin down the shafts, waiting a few hours, then gently forcing them around with a vice-grip. Only had to replace one of eight or nine pots. Never know what will save the day.

Everybody's (almost) lookin' for that miracle cure in a spray can. We know better. It takes elbow grease and brain power. And just a dab of the right stuff in the right place.

[Enzo]

I like slick, easy to turn pots myself. The vaseline type stuff they stick in pots for grease does make them turn stiffer. Some of the old Tapco mixers turned so stiff you could barely move them with just your fingers. In the shop I used to work in, we had a con of some thinner. I forget what it was, had a very chemical sounding name. Xylothaline or something. (No, I made up that word, I forget the real one) This stuff, I was told, came right from Tapco, and was intended as a solvent for that grease. You thinned th grease so your controls could even be turned.

[km6xz]

I went to pepboys and bought some CRC brake clean ( fast drying oil and grease remover with no residue, basically acetone) and cleaned all relevant contacts .

ta da!! amp works like new! better than it has in ages.
proving once again the old adages;

Unfortunately, by using such a "dry" cleaner/degreaser you will likely find that the oxidation and corrosion suddenly returns much worse than before.
Metal contacts normally have a thin layer of oxide of the metal, which is an insulator. That is good, with a thin layer, further oxidation is retarded yet remains so thin that despite being an insulator, normal operations voltages or signals can span the barrier. If oxide of the metal becomes thick, intermittent operation or the "scratchy" pot sound is the normal result. Some metals are intentionally surface corroded or oxidized during the manufacturing process such as when smelting aluminum, a protective layer of Aluminum oxide is encourages because as with most metals, atmospheric oxygen reacts quickly with the metal. Aluminum oxide looks grey and that color is called "aluminum" but without that oxide layer, aluminum is bright and shiny like chrome when first smelted.

When contacts become impacted by thick oxide, de-oxidizing agents like DeOxit are applied to react with the metal oxide which breaks the metal-oxygen bond. The de-oxidizer has additional ingredients that form an oxygen barrier to prevent re-combining of the metal and oxygen, or else oxidation would return faster then before when there was a thin protective layer. That coating is important in providing the oxygen barrier because a metal devoid of any oxide layer will corrode very fast, like in the first few seconds of metal processing from ores. Using a strong degreaser or cleaner washing away the protective coating subjects the non-oxidized metal to rapid corrosion. Cleaners and degreasers are the worst thing to clean metal with if electrical contact is expected to be maintained.

Go back and treat any metal contact surfaces with DeOxit again before the surface is damaged. The mistake was in first applying it badly, de-oxidizing agents are not "cleaners" so a lot does not clean a lot, it is a chemical bond breaker that is effective just coating the contract with a thin layer. If you need to clean a pot or connectors with a wash, Tuner Wash of other flooding agent will work but apply DeOxit as the last step to apply the protective oxygen barrier. Any more than barely there is a waste of deoxidizer and gets contaminated with dirt which is potentially conductive. If you can see it, after application, you used too much.

I usually use a small syringe for application of deoxidizer on the contact surfaces only. Spraying is overkill and risks getting it on the shaft of pots which washes out the lubricant. That makes them loose, gritty and missing their smooth damped feels. Caig Laboratories makes a Moving Contact Lubricant that can help improve the feel but it is not as good as the grease originally applied by the manufacturer to get that smooth damped feel.

[Steve Conner]

While Stan is technically correct about oxide films, electrical contacts are carefully made out of, or plated with materials that don't form thick oxide films, for this very reason. If there is a problem with corrosion, the real problem is probably that the plating has worn off. Having said that, cigarette smoke, polluted city air and salty sea breezes can mess up just about any metal.

In contact design, there is a trade off between handling high currents without destruction, and handling small signals without distortion. Silver is a good general purpose material, but it tends to form a sulphide layer in city air, causing horrendous distortion or even a complete loss of signal. Gold plating is best for small signals, but even one high-current switching event will burn it off.

Signal switches in audio gear should really be hermetically sealed with gold contacts, but almost everyone uses cheap silver-plated parts instead to save money.

A while ago I was experimenting with building low-distortion hi-fi amps. A few years down the line, the biggest source of distortion in my prototype units is the speaker relay contacts, 10x more than the rest of the electronics put together.

The hi-fi speaker relay is probably the hardest contact problem in audio, because it has to handle small signals without distortion and large ones without destruction. I'm experimenting with solid-state alternatives.

[bob p]

I've had similar problems with mechanical amp protection / speaker protection relays in HiFi gear. As Steve said, everyone cheaps out and uses silver contacts becuase they're "good enough." In other words, they'll last through the warranty period. Then, even though they're packaged in little plastic boxes that are supposed to be "hermetically sealed," they do oxidize over time. I've had HiFi amps with silver plated relays where the oxidization had gotten so bad that the relay stopped conducting signal. How's that for distortion?

Unfortunately, you're often between a rock and a hard place when trying to find replacements for these sorts of things. In my case, I was looking for a PCB mounted relay for a 30 year old amp with silver contacts, and I had zero luck finding a replacement. In the end I had to source the best relay I could get, mount it in the chassis, and run jumper wires to the speaker terminals on the board.

Unfortunately, I've got a bunch of SS gear that thumps on power-down, and I'd really like to avoid the nasty noise, but I just can't bring myself to put a relay in the signal path.

MOSFET switching does seem like a better option. What kind of work have you done, Steve?

[drewl]

Everything in moderation.

One place I used to work had some kick ass old school contact cleaner for heavy duty high current contacts.
I sprayed some in a pot way back when I was a noob and it melted the cheap ass plastic!

[Leo_Gnardo]

I sprayed some in a pot way back when I was a noob and it melted the cheap ass plastic!

Oh yeah, done that. Radio Shaft spray cleaner into a QSC crossover @ 1978. Knob spun round and round and round and round and ... then fell out. DOH! Not long after that found Cramolin red and blue in tiny dram bottles. THAT worked mucho better. Still have mine, not a quarter used up. Maybe some collector will pay big moolah for vintage Cramolin?

[Steve Conner]

I basically rediscovered Rod Elliot's work on the subject. ESP - MOSFET Solid State Relays

For my prototype I used some extremely low Rds(on) MOSFETs driven by a photovoltaic isolator. Rod shows a JFET turnoff circuit, but the PVIs I used had this circuit built in.

Because of the extremely high gate capacitance of the large MOSFETs, and the PVI's wimpy current output, it takes the best part of a second to switch on, but at least the turnoff circuit switches it off quickly, which is what counts to remove turn-off thumps and break the circuit in an emergency.

To characterise the distortion performance, I measured the distortion in the voltage across the MOSFETs' Rds(on) when driving 100W into a 4 ohm load. It was about 0.3% and mostly third harmonic. This extrapolates to about 0.003% THD added to the amplifier output as a whole. Still worse than a Blameless-type solid-state amp can manage at 1kHz, but better than a speaker relay with dirty contacts, and completely inaudible I bet.

The prototype MOSFET speaker relay is currently undergoing testing in one of my old amps with a particularly vicious turn-on thump.