Fixing broken mouse button on a Logitech M705 Marathon mouse (cordless) - Logitech M705 Marathon mouse taken apart

Some weeks ago I fixed my Logitech LX6 mouse, this week came time to fix my Logitech M705 Marathon mouse.

I knew it was coming... some months ago the M705 started to make unexpected double-click, and today it reached the "can't stand it no more" level :-)

The plan is the same as for the LX6 fixing... but this time I used a dremel to loose less time in desoldering/removing the switches.

I must say that the disassembly of Logitech product is always interesting, I think them are very well engineered.

Here we go with some detailed photos of the Logitech M705 internals.

First, there are the screws, 5 screw to be precise.
1 screw directly visible on the right,
2 screws under the sticker inside the battery holder,
2 screws under the big mouse feet on the left (in the photo you can see the hole for the already removed screws)

Now you can open the mouse

 

The assembly of the free spinning wheel is very well done!
Wheel, please, look to the left...

 ...now look to the right.

And here is the mechanism that switch from free-spinning, to the classical click-spinning.
When you push the button on the mouse, there is a tiny hook that engage the notch inside the wheel.

Here the hook is engaging the notch, and the wheel is in the classical click-spinning mode.

In this other image the hook is disengaged, and the mouse is in free spinning mode.

It's just a 1mm difference... but the free spinning wheel is amazingly useful (especially when you are a software developer and need to scroll trough thousand on lines of code :-) )

Another view of the wheel, and the switch.
The broken one is the switch of the left mouse button.

Now came to the interesting part: how do we remove the wheel assembly?
It turned out there there is a tiny plastic pin that hold it in place.
If you remove this pin...

 ...you will be able to lift and remove the wheel assembly!

Yeah, now I can have a better look at the circuit board...
...and establish that the board is still firmly locked to the case.

There are 4 more screws to remove...

...but first you need to take care of these 2 tiny spring, they will keep the wheel stright, so don't loose them.
They are just placed in their hole, so gently lift hem and put them in a safe place.

I use some tiny neodymium magnet to hold all the different screws/spring in a safe place.

Then get a tiny screwdriver, and remove these 4 screws: you'll find out that these screws are STRONGLY tightened to the board.

After removing these screws, and some more plastic, you can observe some switches in not wildly used form factor, it's interesting....

Finally I can remove he main board... opps...
I thought I can remove it, but ther is more under the board: there is a tiny circuit for the hidden thumb mouse button.

 Some other screws to remove...

Then remove this piece of plastic...

 and unhook the last piece of circuit from the case.

 Eureka: Finally free!
 The M705 main circuit board in all it's glory!

  

Now it's just the same old story:

1. Desolder the the old broken switch.
   (typically this is a sequence of: cut, heat, push, pull, heat again, cut, use your light saber.... until you get the switch out without breaking the main board)
2. Resolder a new working switch.

With this particular switch I've had some issue: 1 of the 3 pin war very stiff, I had to pull a lot.
Even after desoldering and cleaning the board, it's been a complex job to push the new switch in it's place.
I had the feeling that I've been very near to the breaking point of the copper under the board.
Anyway, I've eventually been able to replace the broken switch with a working one.


A final note: if you, like me, are thinking about using a dremel to speed up the "broken switch removing" part, here is what happened to me...


By not having a welder tip specific for desoldering, the only working way I found for removing a mouse switch is by breaking it in 3 part, and desolder them individually.
This time I tried to use a dremel to break the switch in 3 part more easly and less aburptly than by using a nipper.

For the most part, the idea worked out well... but you need to pay attention when you have a 10'000 rpm spinning diamond coated 120 grit burs.
If you loose control of it, you may end up with something like this, look at the 4 tiny smd resistors/capacitors in this image, just under the broken switch:

Here is a bigger image.
I nearly ripped off a capacitor, and damaged the soldering on the two nearby resistors/capacitors.

Another image or the scraped smd components.

After all, I've been very lucky, the mouse still seem to works perfectly.
Probably there still is enough tin on the side and maybe under the smd capacitor.

But still, sometime, I look at my mouse and I ask myself: how much will it last now? :-)

Fixing broken mouse button on a Logitech LX6 cordless mouse - Logitech LX6 mouse dismantled

Some years ago I was looking for a cordless mouse. The mouse cable was becoming an annoying thing... But I didn't want to change the mouse's batteries every month.

Then a new model came out: the Logitech LX6 Cordless Mouse, and it was reported to have 6 months of battery life.

So the Logitech LX6 became my first cordless mouse, and I've been very happy with it.

I must admit that after the LX6 I've been totally sold on Logitech Cordless mice, so now I own: the Logitech LX6 (used by my wife), the Logitech M705 'Marathon mouse' (on my main PC), the Logitech MX Revolution (at office), ad the Logitech V550 Nano Cordless Laser (on my netbook).

Now, after may years of happy clicking, the right button of the LX6 started behaving weirdly.
I know it can happen: the switch under mouse button can break/wear out, and suddenly your mouse start to triple/quadruple-clicking anything you are staring at.
Exactly for this reason I have a box with some broken mice: so that I can reuse their switches to fix my mouses :-)

Normally this is just a matter of desoldering the old switch, and soldering a new one.
But with the LX6, the first relevant thing to do was embarking in the (not so) easy process of taking it apart.
So here I'll show you some photos of the LX6 interior, and what you need to do to take it fully apart.

My Logithech LX6

The first 2 screws to remove are under the mouse feet.

The other 2 screws are inside the battery holder.

Now the LX6 is opened, but there is still much to do before you can remove the main circuit board.

Here is a shot of the broken switch.

And here is the "actuator" of the broken switch, it's the piece of plastic under the mouse button.
Even this plastic was a bit worn, so I tried to "fix" it with some drop of glue. But as it turned out, it wasn't this worn plastic causing the problem, but the underlying switch.

After detaching the connector, you are left with 2 mouse pieces, and the main board still firmly locked in it's place.

Guess wath? there is another screw that hold the mouse scroll wheel.

After removing this screw, we can take a look at the scroll wheel.

But the main board, is still locked.

At this point, I noticed the the battery holder is a separate piece of plastic, let's get rid of it.

There is a clip that hold the battery holder. A tiny screwdriver is enough to unclip it.
Remember to detach the battery connector before unclipping the battery holder.

And then, after unclipping the battery holder...

...it will slide out of its, ehm, holder.

And now we can look at the LX6 battery holder in all it's majesty :-)

Finally, we will be able to remove the main board.

 
Just unclip the IR Led, detach the flat cable of the IR sensor, and the main board will finally come out.
And we are left with a near empy bottom mouse plastic shell.

I like the simple way Logitech engineered the 2 buttons under the mouse.

Anyway, we finally can look at the main board of the mouse.

And here is the soldered joint of the culprit that made this mouse quadruple-click anything.

Here, near the broken switch, there is the replacement: the red switch, directly from my box of broken mice.

When I need to use the solderer, I remember why I decided to get a degree in Information Technology instead that Electronics :-)
Anyway, I'm glad I also studied Electronics, at least I know how to build ant fix electronics things ! :-)

Now the plan is easy:
1) desolder the broken switch from LX6 board.
1.1) don't break the main board
2) desolder the working red switch from the broken mouse
3) solder the working switch on LX6 main board

Desoldering is hard, especially if you need to desolder things hat are soldered on both side of the board.

After about 60 minutes of fiddling with solderer, tin sucker, and a copper wire used as a tin sponge/sucker...  I've been able to remove the broken switch, and now I have a pretty clean (and luckly still intact) main board :-)

 
Desoldering the working switch from the broken mouse is easier, because "saving the board" isn't included in the plan :-)

The last part of the plan, soldering the working switch on the LX6 board, is just a matter of seconds!

And here we have it, the working switch now soldered on the LX6 board!

Now my Logitech LX6 is ready to go for another bunch of years of happy clicking! :-)

P.S.: no working mice were harmed in the making of this post :-)