I have not used it but just bought a spray can of Deoxit. From reading about it, it seems to be the greatest stuff for cleaning contacts.
I have an old Tectronix Scope 465B that one chanel has a flakey input switch. The manual says only to use isopropal alcohol to clean it with, I did that with some 99% and it helped some, but thinking of using some of the Deoxit on the switch. Would that be ok or not.
I would hate to mess up the switches as they would be almost impossiable to find replacements for .
First recommendation would be "stick to the manufacturer's rules". They may know something we don't.
I've read a number of comments (Hi, Jeff!) that DeOxIt is *not* a good thing to use on gold-plated contacts. Gold plating is often somewhat porous, and the DeOxIt can creep through the pores down to the base metal and may actually attack it. This can cause the gold plating to fail.
CAIG makes a different product ("ProGold") which is intended for gold-plated contacts, and if I understand correctly, it's intended to avoid this problem.
Your Tek's switch may actually be suffering from contact wear, rather than contact surface contamination. If I recall properly, the delicate contact fingers in the switch do "rub" slightly on the contact pads when the switch is activated, and over time this can wear away the gold plating, and the contact don't work well after that. Cleaning (with ispropanol or anything else) isn't going to help this situation more than very temporarily.
I haven't found a solution (so to speak :-) ) for this sort of problem, other than an actual repair of the switch (replace the contact fingers) and as you note, this may not be possible due to lack of available parts.
When in doubt, put some Deoxit on a Qtip and rub the plastic body of the sw itch. Check it for any softening. Try to scratch it with a dental pick. The n try to scratch an untouched one.
The danger is not to the contacts. I have seen acetone and Qdope thinner (w hich is toluene) do some very nasty things to plastic. If Deoxit has either in it you might be much better off sticking with the alcohol. Plus, Deoxit uses a chemical known as a reducer which actually uncorrodes the metal - t hus the name. I really do ot know about the properties of that stuff.
Usually it is best to stay with what the manufacturer recommends, but in this case the Deoxit was probably thought of years after the scope was made.
Thanks for the advice of the Deoxit Gold. Maybe I will try that at some point instead of the kind I have.
As stated above I have been repairing some electronics over the last 40 years as a hobby and never tried the Deoxit. As all reports seem to say this stuff cures anything that WD 40 won't.. ( I never use WD 40 by the way for various reasons.)
It has been a while from the last time I looked in the scope, but best I remember that while the part you turn is a rotary switch, the contacts are actually slide switches of sorts. Then as it was mentioned it may attack the plastic. Some cleaners do and some don't. I used to use LPS cleaner and never found plastic that it would affect.
That wasn't me. The problem is that Caig has juggled the formulation for Deoxit and/or Cramolin has changed over the years. My main problem with the old stuff was that it uses oleic acid. Nothing wrong with that since it's the acid that removes the oxides from the contacts. The problem is that it will also attack copper if left on the contacts for too long. I also found that I can make things worse by mixing my own and using too much oleic acid. It will not attack gold or silver plated contacts, so those are safe. So, if you're using the old stuff with oleic acid, wash off the contacts with alcohol after you've removed the black silver oxide coating.
Gold does not oxidize so using an oxide remover on gold contacts is a total waste of time. At worst, gold contacts will have a layer of tar produced by the last attempt to lubricate the contacts.
The rest of the formulation is some form of naphtha. Lots of things contain various forms and mixes of naphtha. Usually, lighter fluid is mentioned, but that might be to volatile. I use Coleman camp fuel, which works well enough. Or, just buy the pure stuff: They all work.
Now, for the switches... Think about what you're trying to accomplish. You're trying to remove a layer of some kind of oxide from the contacts. You're also trying to remove any tar left over from the previous attempt to lube the contacts. Any mild acid and organic solvent will do that. You don't need anything super strong. If you want something with some lubricant added, use contact cleaner, or maybe mix in your favorite oil. Just make sure it doesn't turn into a sticky tar when it evaporates.
Summary:
- If it's gold contacts, use alcohol because there's no oxides.
- If it's silver contacts, use contact cleaner, Deoxit, Cramolin, or whatever removes the black silver oxide from the contacts. Then wash it off with alcohol and leave it alone.
- I'm not a big fan of grease and oil as a contact lubricant.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
I stand half way corrected. Y'er right. Most of the tarnish is silver sulphide. "This dense black solid constitutes the tarnish that forms over time on silverware and other silver objects." Also, silver oxide is also dark colored: "Tarnish" is a mixture of silver oxide and silver sulphide, in proportions that vary with whatever is causing the silver to tarnish. Silver sulphide tarnishes rather quickly in the presence of sulphur bearing compounds, while silver oxide takes months to accumulate. "...silver needs hydrogen sulfide to tarnish, although it may tarnish with oxygen over time."
What do you mean "must become conductive"? Do you mean that the oleic acid becomes conductive, or perhaps the contact cleaner? Unlikely because the oleic acid will attack copper and therefore must be washed off by something after its used to clean the oxides, sulphides, crud, dirt, tar, and oils off the contacts.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
The Deoxit I bought a few days ago must not contain any of the oleic acid. Not mentioned on the can. This is Deoxit D5. The can says it protects surfaces so doubt this is a copper eating compound.
The directions say to spray and activate the knobs. Then give it a short spray and wait 2 minutes before turning the equipment on. I guess that the wait time is to make sure any thaing that burns has evaporated. There is no mention of cleaning it off, but really should be left on the contacts from the way I read it.
When I was working overseas in a country where all products were required t o have all contents listed in clear terms, Cramolin Red had a paper label o n it that stated: Ingredients: Oleic Acid 5% Petroleum hydrocarbons and pro pellants 95%. It also cost only about $4 for a 300 ml. spray can. Oleic aci d has been around the metals cleaning, clock-making and fine machinery indu stries for well over 100 years and has been used primarily as a degreaser a nd oxide remover, primarily for those metals containing copper, tin or zinc . Covers much of what we do here.
In the US, Caig once had a relationship with Cramolin - selling Cramolin's products packaged for US markets. That relationship failed. And - the story behind the Caig Company, DeOxit, Cramolin and Cramolin Red is fascinating and does not reflect well on Caig.
Here's part of the story: I'm not sure if the story allegedly from Mr Graham, prez of Caig rings totally true. The "hazardous material" story seems to be a cover for a financial arrangement that went awry.
I still have a small bottle of Deoxit R-100L. Over about 20 years, I've only used half the bottle, mostly because I dispensed it by the drop with a syringe. Q-tips and sprays are wasteful. However, for my day to day stuff, I mix my own secret formula cleaner. It's secret because I never mix the stuff accurately or twice the same way. I also can't recall exactly what I tossed into the stew last. I think it's mostly naphtha (Coleman lantern fuel), a little oleic acid, and some automobile engine oil phosphorescent dye so I can see where I slopped the stuff with a UV light. Or, maybe it was some solvent red
26 dye. Ask me again in about 5 years when I'm scheduled to run out and need to mix another batch.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
The problem here is the MSDS only lists ingredients that are deemed hazardous. Oleic acid is food safe and might not be listed. If you look on the can somewhere, you might find the product number. Then look it up here to see what's inside: Don't be surprised if it says "proprietary ingredient" or something similar. The SDS sheet is nearly useless.
Taking a wild guess, I blundered upon: which offers: PETROLEUM NAPHTHA 75% DIFLUOROETHANE 20%
Oh well. That's probably the Deoxit product that Caig was reselling back in the 1980's.
Find a piece of copper. Drip on some Deoxit. See if there's any green colored corrosion. You may need a microscope to see it.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
They do not list the % on the can I have,but that is what is in it on the lable for the can I just bought.
I sprayed some on a piece of copper PC board so will wait overnight and see if it turns green.
I wish the government would make the companies list everything the put into the products. Not being able to hold back as far as a trade secret. I don't care what percent, but do care about what is in it.
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