How to clean screw terminals and spade contacts?

[tggzzz]

For my sins I've just purchased a Julie Labs 7 decade Kelvin-Varley Divider, and as far as I can tell, it works to spec

However, the screw terminals and spade contacts on the wires have the patina you would expect on a device that was probably manufactured in the 50s. So, what's the best way of non-destructively cleaning them?

A couple of parameters:

• I'm not interested in aggressively stripping back to pure copper. I'm not a metrology lab, so I'm interested in repeatable practical connections - and not interested in the ideal but impractical connections
• available chemicals are IPA, meths, Caig DeOxit, or anything else that can be justified

The terminals, shown below, don't look too bad. The spades connectors are muckier, but more easily replaceable. (The cables are very stiff, and feel like homebrew PTFE wires)

The "do nothing" option is perfectly reasonable - and is preferable to permanently fouling things up.

[Gyro]

Strange as it may seem, Vaseline! I've used it on tapered plugs, brass terminals etc. and it improves contact quality no end. It also stops the terminal threads binding and galling.

Smear on once and exercise them. Wipe off any resulting muck. Then re-apply a thin smear to maintain protection.


P.S. Don't leave screwdriver marks an debris in the tub, your other half will notice. I have my own dedicated tub now. 

[Ian.M]

Mask off the front panel, then use contact cleaner and a brass brush to get the oxides off the contact surfaces of the screw terminals.  A brass brush will be soft enough not to significantly abrade the metal surface.   Once no more muck comes off when you wipe, go with Gyro's suggestion.   The spade terminals will probably clean up satisfactorily the same way, but if there's any doubt about the integrity of the joint to the wire, you may be better off cutting back the wire and re-terminating them with new crimp terminals.

You'll probably need to carefully clean the exterior of the terminal post insulators after cleaning the terminals to reduce leakage.  Lighter fluid (Naptha) followed by IPA should do the job, or if you have a proprietary zero residue contact cleaner, use that.

[tggzzz]

I certainly use vaseline on my car battery terminals; the last time being last Thursday!

I'm a little reluctant to use it on uV level circuits without being sure there would be no "interesting" chemical reactions. The same is true of any other mechanism, of course.

Thanks for your suggestions, and I look forward to other people's comments.

[helius]

Mineral greases like Vaseline have a long history of use as rust inhibitors and contact protectants. You can still find them offered as "dielectric grease", Cosmoline, and No-Ox-Id. Some of the heavier waxy greases were intended for long-term storage protection, as when a battleship is mothballed. They do work well on things like light bulbs where you want to prevent seizing or spalling, but for low-level signal contacts DeOxit might make more sense.

[dacman]

I use a touch of mineral oil on a cotton swab.  It's been my experience that gold-plated contacts last much longer if the surface is cleaned from any grit or contamination and slightly lubricated.  For any oxidation, I use DeoxIt, or sometimes DeoxIt-Gold.

[IconicPCB]

Ammonia based solvent and cotton buds

[Electro Detective]

A fast fix is standard WD-40 sprayed into a container and applied carefully to affected metal areas with a cotton tip/Q tip

One application should get the crud moving, a second app to keep parts lightly lubed and looking good   


FWIW: you can always go the the contact spray lubricant of your choice at a later stage,
after the WD40 has done all the hard work and removed with isopropyl alcohol first etc

[tggzzz]

Thanks for all of these suggestions.

Is there anything that manufacturers of metrology equipment specifically recommend?

[tggzzz]

Here is a parallel conversation: https://www.eevblog.com/forum/metrology/contact-cleaner-for-metrology-grade-connections/

I suggest we avoid duplication by moving the conversation to that thread.