🖱️Replacing the Left/Right Click Tact Switches on the Logitech MX Ergo S

The left click on my trackball mouse, a Logitech MX Ergo S MXTB2 (MR0113), started to chatter (register double clicks), so I repaired it by replacing the switch.

I found several posts about replacing the switches on the previous model, the MX Ergo, but there was little information about its successor, the MX Ergo S, so I am recording the replacement procedure here.

• Do this work at your own risk. If the repair fails, the mouse may be completely broken.
• Opening the mouse voids the manufacturer's warranty. If it is still under warranty, I recommend contacting official support first. (Logitech is likely to replace a mouse for click chatter while it is under warranty.)
• The MX Ergo S uses tact switches, not the microswitches used in the older MX Ergo. Be careful not to buy microswitches by mistake. (I bought microswitches without checking the board inside first.)
• Do not use contact cleaner spray. The switch construction differs from the older model.

  When I sprayed contact cleaner on the left and right switches, both of them, including the right click that had been working fine, lost their click feel and were completely ruined.

• Tact switches: for the left and right click

The following silent-type Kailh tact switches, 6 mm × 6 mm × 7.3 mm with 2 pins, fit the board: Kailh silent tact switches for mouse buttons, 6×6×7.3 mm, 20 pcs (Amazon Japan)

I chose this part based on this post on X:

Unlike the microswitches used in the older MX Ergo, the MX Ergo S uses tact switches. Check the size and shape carefully before buying.

• A hex lobe (Torx) driver or bit for T6 screws: needed to open the cover

  The screws sit deep inside the housing, so the short bits in a typical precision screwdriver kit get stuck in the hole and cannot reach the screw. You need about 15 mm of narrow tip that fits into a hole roughly 4 mm in diameter, so either buy a standalone driver or use a long bit.

  I used a set of hex lobe bits that attach to the electric ball driver shown below: ANEX hex lobe color bits, 65 mm, 5-piece set (T4/5/6/8/10) ACTX5-65L2 (Amazon Japan)

• Precision Phillips screwdriver (PH00): needed to take the board apart after opening the cover
• Soldering iron
• Rosin-core solder
• Desoldering pump or desoldering wick

The following are optional electronics tools (handy to have, but substitutes work):

• Tweezers and needle-nose pliers: used to remove the flat cable and to detach the wheel

  ENGINEER ceramic tweezers PTZ-51 (Amazon Japan)

  Fujiya micro needle-nose pliers MP6-150 (Amazon Japan)

• Reverse-action tweezers: handy for holding the board, and also used to pull the switch off

  goot reverse-action tweezers, small, TS-16 (Amazon Japan)

• Isopropyl or anhydrous ethanol: can be used to clean flux off the board after soldering (a dedicated flux remover is even better)
• Soldering work mat: to avoid scorching the desk

  KaiYi soldering work mat, 35 × 25 cm (Amazon Japan)

First switch the power off and remove the trackball, then remove the six screws on the underside of the mouse with the Torx (T6) driver.

Once all the screws are out, separate the top and bottom covers. Hooking a fingernail into any gap around the edge makes it fairly easy to pry apart.

Disconnect the flat cable that runs between the top and bottom covers from the board.

To release it, pull the black latch on the board connector upward with tweezers or needle-nose pliers, then pull the cable out. (Be careful not to pull so hard that the latch comes off.)

If you have used the mouse for a long time, grime and dust will come out from deep inside the board, so clean as you go while taking it apart.

Next, remove the screws holding the board and the other parts and take out the main board.

There are many screws, so keep track of where each one came from.

The rough procedure is as follows. Taking photos of the screw and connector positions before disassembly is a safe idea.

1. Disconnect the connector going to the battery and remove the screws of the battery mount
2. Remove the screws of the board at the top left
3. Remove the wheel assembly (push the front axle upward with pliers to release it)

   

4. Once all the flat cables and board screws are removed, the board can be taken out

With the main board out, start the switch replacement. The parts to replace are the yellow tact switches for the left and right click.

First, remove the switches.

There are several ways to do this; here is how I did it. (This method works when the solder cannot be sucked away cleanly and you do not intend to reuse the removed part.)

1. Hold the soldering iron on the switch terminals on the back of the board while feeding in extra solder (the original solder is hard to melt, so adding solder supplies fresh solder and flux)
2. Wedge reverse-action tweezers or similar into the gap between the switch and the board
3. While melting the solder on the terminals, push the tweezers in deeper or lever the switch up to remove it

After removing the switch, clear the remaining solder from the board with desoldering wick or a desoldering pump. It is enough if the holes are clear enough for the pins of the new switch to pass through.

Then fit the new switch. Push it in until the switch sits flush against the board, then solder the pins. Holding the switch down with reverse-action tweezers ensures it stays flush.

Once soldered, wipe the flux residue off the board with flux remover or anhydrous ethanol.

Reassemble in the reverse order of disassembly.

For the flat cable, lift the latch, push the cable firmly all the way into the connector, then press the latch down to lock it.

Test it, and if the clicks work normally, the repair is done.

Since I switched to silent-type switches, the click sound is also quieter now.

It takes a bit of effort, but the repair was far cheaper than buying a new mouse.

The durability may not match a brand-new mouse, but I have spare switches left (the pack I bought contains 20), so if it fails again I can replace them and extend its life once more.

If your out-of-warranty MX Ergo S starts to chatter, I think it is worth trying a switch replacement yourself before buying a new one.