Removing tarnish

[SoulFetish]

Problem solved. Diluted some Brasso with a bit of warm water, soaked all the jacks in it for a little while, shaking the container every now and then, and gave them each a low-effort scrub with an old toothbrush, and sparkly clean.

I will have to remember this technique next time I need to clean some jacks. I'd like to try this in some of my old tube sockets as well. Although the quality and price of Belton's tube sockets make it more and more difficult to justify using anything else these days.
I've had a lot of success polishing out oxidized/tarnished terminal contacts using a touch of Mother's mag polish and microfiber cloth. The trick is lightly make sure to orient the microfiber "grain" to run in the direction of the polishing motion, if that makes sense. But you can't really polish out connectors like 1/4" jacks that way. So I'm glad you reported back on some success.
As a total aside, I keep waiting for someone to manufacture a proper polishing tool or applicator around the size and shape of a q-tip, but lasts longer than 2.3 seconds before it completely falls apart.

[Mark Hammer]

I should qualify my success by noting that the jacks were not heavily oxidized. They just all had enough discolouration from tarnish that I wanted to check them off the list should I need to troubleshoot anything I had installed them in.

Something more oxidized might require direct application of undiluted Brasso, and a bit more scrubbing that I had to engage in. But I hope my success can generalize to other folks.

[Chuck H]

All true. Removing brass oxidation is all abut mechanical effort. The oxide film IS thick enough to foul low signal/voltage electrical contact and the oxide layer is thick enough to not be removed by wiper motion on switch contacts. Brass is a poor surface material for electrical contact for this reason. Though many non soldered electrical connectors are made from brass for it's conductivity, ease of tooling/plating and it's shape resilience. But brass contacts are usually plated in nickel or some other low/thin oxide prone metal that allows wear of the sparse oxide with mere switch contact.

I guess what I'm saying is, brass alone is not a good contact material, and mechanical oxide removal is the best solution.

[Enzo]

Wow, Brasso. I haven't heard of that in years. I think I saw some in my mom's cleaning closet. Along with other odd products like carbon tetrachloride.

[Chuck H]

I thought the Brasso product included a hard wax component as protection against new oxidation too quickly. I've used it plenty for all kinds of things but I never even considered it for cleaning contacts because it smells like it has a hard wax (insulative) component. I could be wrong, and I probably shouldn't judge a product based on my olfactory senses But most products of this type include a wax of some kind as protection from oxide formation and Brasso smells like that. I'll have to look in my cubbies and see if I still have any and red the label to see.

[Enzo]

The label of Australian Brasso lists "Liquid Hydrocarbons 630g/L; Ammonia 5g/L", whereas the material safety data sheet for Brasso in North America lists: isopropyl alcohol 3–5%, ammonia 5–10%, silica powder 15–20% and oxalic acid 0–3% as the ingredients.[4] However, the Australian version contains kaolin instead of silica for abrasives.[5]

From the Wiki...

[Chuck H]

Yes, it appears that Brasso is just a very mild abrasive. I've been through many and various bottles of metal polish, some of which do contain wax. I'm probably incorrectly applying an old memory to Brasso.

[Mark Hammer]

I installed a pair of the jacks on each of a half-dozen modules this morning, for a large-ish modular effects system I've been working on for damn near a decade. Have not wired them up yet, so the real test will be whether I get decent or intermittent contact, once everything is wired up later this weekend. Hopefully, whatever residue Brasso might leave behind, that is not planned around electronic efficiency, will have been rinsed away with warm water.