Take the switch arrays out and wash and scrub with with Dawn dish detergent. Rinse throughly with water and then with 97% IPA and let dry. Then apply DeoxIT (red) spray while rotating the switches. Let it dry 24 hours. Optionally apply DeoxIT Protection (blue) spray as above as well for additional corrosion protection.
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Unfortunately all these proprietary brands of stuff are not so simple to find in the rest of the world. Dawn dish detergent? Is that like Fairy Liquid? I normally hear of something called "Simple Green" which seems to be the industrial detergent of choice in the USA. Now 97% IPA is something I can easily get ahold of (I've got a gallon of 99.9%). But then you present DeoxIT (red) and (blue). WTF are they? Some versions available from Farnell but very pricey compared to other contact cleaners in the UK and to be honest I really don't want to spray anything on my equipment if all it has is a brand name and some anecdotes.
Now I've had good results from using the local cheap contact cleaner that all service shops use, Servisol Super 10. But thats on shitty old TV's and VCR's or anything with crap switches, trimmers and pots. I really would not dream of spraying any old shit like that on a very sensitive analog board, say in a 6.5+ digit meter or a precision resistor decade.
What I am getting at is there must be some proper methods of cleaning contacts based on the materials they are made of and the proper chemicals to use rather than some magic "works wonders" nostrum, given a brand name and then different "colours" too because the magic elixir is not selling so well anymore...
LOL. No, DeoxIT isn't snake oil. It's very well respected and pretty much the best of the best for contact cleaners.
There's three main versions: Original (red colored), Gold (yellow, for cleaning gold plated contacts) and Shield (blue, used after original to provide additional corrosion protection in harsh environments).
There are also several formulations and applicators available. There's two versions of the aerosol spray: D100 and D5. D100 is pure DeoxIT and D5 is 5% DeoxIT, the rest being IPA. The advantage to the latter is you can spray it inside a semi-sealed switch, as the IPA evaporates leaving just the DeoxIT. D100 must be wiped off the contacts once applied. (I only buy D100 now; if I want to clean a switch or something where I can't directly get to the contacts I simply mix 5 drops of D100 with IPA and use a syringe with a 16ga needle to inject it right where I need it; works great!)
Anyway, this stuff has been around many years and there's hard science behind the effectiveness. It's expensive, yes, but from my experience nothing works better. I've restored at least one hundred pieces of vintage test gear, so I'm not talking out my ass here.
Sorry for assuming you were in the US; Dawn is a common degreasing dish liquid here. (It works so well they use it to wash birds and other animals after oil spills; seriously, it's true!) Any degreasing dish soap should work, as long as it has no fragrances or anything.
Fun Fact: Back in the day, when Tek got scopes in to refurbish or repair, they would literally wash them. With soap and water. CRT, circuit boards and all. They'd do a rinse with deionized water (deionization removes minerals and other contaminants, which is what causes water spots) and dry it in a oven (at low temperatures, of course).
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