It took me a while to understand the key mechanism because it was different from the one shown in the first video I watched about this topic. Anyway, after several tests and with the help of my son Fernando (yes, he’s helping 👏), we figured it out.

NOTE TO SELF: If I had watched this other video, I would have understood it in minutes. But what’s the fun in that? 😄

How it works

  1. The small square (1) inside the key is actually made of two metal pieces sandwiched together.
  2. When a key is pressed, key holder (3) moves down and pushes the center of the metal piece that looks like a Y (2) against the center of the square (1). That’s what closes the circuit and registers the key press.
  3. There’s also a spring (not shown in the picture) that brings the key holder up again after the press.
Four disassembled parts of a mechanical switch are laid out on a green cutting mat, with labels indicating where a spring should be placed.

To disassemble it, you have to gently pull outwards the two mechanisms that connect the key to the PCB, and the flat plastic tabs that look like a fat T. But be careful, this is old material that easily breaks.

A mechanical keyboard switch is placed on a green cutting mat with a grid pattern.

Fixing

In most cases, the solution is simply to bend the Y-shaped metal (2) piece back to its original shape. I think it gets flatter and flatter over time, and the key holder ends up not being able to press it with enough force agains the piece (1).

A small black switch with metal contacts is placed on a green cutting mat with grid lines.