Can the brushes in a DMM rotary switch be "steel quenched"?
(not sure if that's the correct term, want them to press harder on the PCB contacts, and be more elastic)
I have a cheap clone of an my64 DMM (3.5digits) but with absolutely superb LCD visibility and instant power up. Other much better and more expensive DMMs I have are absolutely horrible in display readability, speed and battery consumption.
I don't know what happened with that type of crystal-clear 7 segments only type of LCD, and with the black blob die straight on PCB stile of ICs, or why they went extinct, but I digress.
The problem with this my64 clone I have is bad contacts in its rotary switch. Under the microscope, the contact springs and the PCB plots look clean. I suspect, the cause is that the mobile brushes lost their springiness, or didn't have enough of it.
Last time I've open it, some years ago, cleaning with izopropil 90% didn't fix it (contacts were clean already). Bending the brushes a little more, made it work a few more years, during which years, it slowly become more and more unreliable.
If iron can be hardened into steel by adding carbon then fast crystallization (for example, turn an iron nail red hot with a torch, then throwing it in a jar of water will harden the metal), would that work, too, for the brush contacts alloy?
Would prefer very much to keep this DMM, any other advice for how to fix the rotary contacts?