Rotary wafer switch cleaner?

Any electronic contact cleaner will help. Ages ago, General Cement (or a company with name similar to "chemco"??) made "De-Oxide" in two forms (prolly had different trade names): concentrated (dark orange or reddish, transparent), and "standard" or normal dilution (pale orange, transparent). This stuff was made eXpressly for silver contacts; would remove oxides, sulfides, and other junk off the contacts, and add a thin protective film of some kind of oil. You would not believe how good the De-Oxide was on very crappy totally nonconductive silver contacts (in TV tuners). Used the standard version for all normalcontact cleaning, and De-Oxide for nasties. The better contact cleaners now have silicone as the protecting "oil" or agent. There may still be a "contact cleaner" that is sh*t and should be avoided at all costs, but i do not know what brand that was/now-is; think it is in a spray can. I think "blue ice" may be the name of one rather nasty crap; avoid anything that sounds like it "repairs" - especially if the blurbs imply that the crap is conductive. That junk slowly spreads ("crawls" is a term that some use), creating conductive paths that should never exist. I hear it is hard to remove.

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Thanks for the heads-up, Robert. I'll try to avoid those products.

John

"The other John Smith" wrote in news:SrXSc.19456$ snipped-for-privacy@newsread1.news.pas.earthlink.net:

I used to use Tarn-X to clean silver-plated switches in TEK tube-type o'scopes.You have to rinse well,then dry in an oven for 3 days to remove the moisture.Then a tuner cleaner/lube spray would help protect the bright silver.

Hi, Jim -

It creates a bit of a problem for me to put a rack-mount instrument into an oven. However, I think your tip is a good one and I'll remember it for use on other items. Thanks.

John

Last month I fixed up an old HP 654A test oscillator whose attenuator was flaky due to bad contacts on the rotary wafer switch. I was not able to get full perfection, but I did get very substantial improvement. (Contacts that had been entirely open-circuit went to between 40 and 500 mohms, but still a little flaky if you wiggle the knob.)

I used Caig Labs "Deoxit", the aerosol in the red can. (I think Caig Labs is the same company that used to be called, or make, "Cramolin.") It took about four or five cycles of spray, wait a few seconds, rotate and wiggle knob, repeat. I put paper towels around the switch to control overspray; but the material itself is *not* conductive or corrosive.

In general I have had good results with Caig Labs products, and I have never found them to cause any damage when used this way.

"The other John Smith" wrote in news:wT5Tc.21076$ snipped-for-privacy@newsread2.news.pas.earthlink.net:

Well,at the two TEK service centers I worked at,we had drying ovens just for that.Those 500 series TEK tube scopes were pretty big.

You could make a temporary drying box and use a bank of 100W lamps to heat it,and a few muffin fans for the 'exhaust',that gives you a negative pressure inside to draw out moisture.

Like a big "Easy-Bake" oven. ;-)

In the specific case of Tektronix scopes, I never believed in contact cleaners. In my personal experience (and yours may be different) the noisy switch issues are generally caused by dust and dirt, not tarnish and wear. I generally flood the contacts with isopropyl alcohol or some other solvent (Freon, in days of old) that dries completely. Then I put the smallest possible amount or Cramolin or some such, the amount that a toothpick will hold, directly on the rotating contact. This solves the problem of oil-soaked wafers which you so often see when contact cleaner has been used. A tiny drop of oil where the shaft passes through the bushing does wonders, too.

I always cringe when I open up a piece of equipment and see the oil spots full of dirt where contact cleaner has been generously used.

Your mileage may of course vary.

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wonders,

I know what you mean. Thanks for the hints.

John

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I'll look up the Cramolin and Deoxit and see about getting some. Thanks for the input.

John