Steelseries Sensei gaming mouse teardown and repair

[olewales]

Hello everyone.

Short intro:
My trusted Razer Deathadder mouse which I've been using for past 7 years finally started to wear out. Scroll wheel encoder and it's microswitch are working very unreliably and plastic body is a bit worn out too. I decided on buying new mouse and I was prepared to spend any amount of money required to buy quality product (If it serves me 5+ years, it's worth it) BUT I am very used to shape of my current mouse. This lead me to buying damaged Steelseries Sensei mouse on auction for about $10 (incl. shipping) just to check how its shape fits my hand and maybe to salvage some parts from it. In the end I managed to repair it, but I am not sure how...

Product was advertised as "Customer return. Sensor not tracking. Probably damaged laser".
Sure enough, when it arrived it was properly detected by computer, all the buttons were working but mouse pointer wasn't going anywhere. I decided to at least see what's inside. Whole construction is held by four screws hidden under "skates" on the bottom of the mouse.
Inside, there are really only 2 ICs:
PixArt ADNS-9500 optical sensor
STM32F103CB MCU

I visually inspected the board for obvious faults but found nothing, expect for quite a lot of flux residue around through-hole components. At this point I noticed that mouse sensor actually moves chaotically when I shine bright light over optical sensor. I was now pretty sure that it's indeed laser illumination fault but using my phone camera I verified that some light was there.

Following first rule of troubleshooting ("thou shalt check voltages") I dug out sensor datasheet and began measuring. It didn't take me long to find that something is wrong. I checked that sensor was configured to use external 3V power supply but on that rail I measured about 4.4V. This wasn't good as IC's rated max input voltage was about 3.6V. Following the traces I found tiny SGM2007-3.3 voltage regulator. It was either faulty or something was shorting 3.3V rail to 5V from usb. One way or another i needed to disconnect regulator output pin from the board. After trying to desolder IC from the board and failing hard I cut the package lead. It turned out that regulator was ok and was providing stable 3.3V when disconnected from the rest of the circuit.

Here is when it gets strange. While measuring the voltage I accidentally shorted package lead back to its pad underneath. And this time voltage stayed on 3.3V. Somehow heating up that area of the board must have fixed the short. I don't know if it was a tin whisker or some other contamination of the pcb or maybe the regulator itself was "repaired" by this process but mouse is now working. Not only all components survived overvoltage on the rail but optical sensor is working perfectly again. I didn't want to blob the cut lead with solder so I added short mod wire to nearby testpoint.

Teardown and before/after repair photos are attached below. I didn't include photos of the top side of the mouse because there is nothing really interesting there and I am already hitting 2MB attachments limit.

Fun fact: Sensor uses infrared laser beam focused (or rather - collimated) to a tight beam. Being infrared it is obviously invisible to a naked eye. UNLESS you stare directly into it. Then it's briefly percepted as quite intensely red color. (it's class 1 laser, I am sure I'll be fine)

PS: I still like the shape my previous mouse better. I'll probably order matching encoder and microswitches on ebay and repair it.

[olewales]

Sorry for double posting, but this is a live situation update.
Ok, I think that that voltage regulator is actually toast. I've noticed some weird mouse movement today (was perfect yesterday) and I took the mouse apart again. 3.3V rail measures 3.65V now. Actually, I suspect that this may not be an isolated case of such failure because there are some reports of those mice gradually losing tracking ability over time. I don't think I have (and will be able to solder) matching SMD LDO regulator but I might have some in TO220 package. I'll post results after I bodge something in.

[codeboy2k]

Nice.  Who knew a mouse has a ARM Cortex M0 in it

If you couldn't get it working, you might have been able to hack it into something useful.

[elgonzo]

LOL. I also was an owner of a Deathadder. I am a leftie, so naturally the left-handed Deathadder attracted me. And that despite having read about numerous accounts of problems with scrollwheel/middle button of Razer mice. And lo and behold, it just took a few months for my mouse to develop scrollwheel issues. Since more than 3 years being "back" to an ambidextrous HP mouse, the kind of simple mouse you get (got?) with their workstations (which also has a proper silicone cable, not this dust-collecting braided stuff). Razer is just gaming junk.

Anyway, much luck with fixing your Steelseries...

[neslekkim]

What kind of scrollwheel issues?, I replaced my deathadder the other day, the wheel seemed to swell up or something, but I had the mouse for many years.
Had an short time with microsoft wireless mouse, but that's crap, so I bought an new Deathadder, the Chroma, very nice mouse

[elgonzo]

Imprecise scrolling. Scrolling by one detent (notch) sometimes led to what felt like two impulses (like scrolling twice). Sometimes just the slightest wiggle on the wheel triggered scrolling impulses. Also clicks on the mouse button wheel didn't register depending on the position of the mouse wheel (rotating the wheel a bit made the clicks register again). While the wheel button could be mapped to one of the side buttons (assuming the application supports this), the scrolling issue was more annoying. Another hilarious thing was the Synapse software (the mouse driver). That was the first mouse driver i encountered that forced you to create some retarded online account with Razer. Fortunately, legacy drivers without such nonsense were still available (not sure if they still are). I also still remember that Razer tried to push their "online" mouse driver through Windows Update. Obviously that thing got immediately hidden/excluded from the update list.

Mind you that was several years ago. I just took a quick peek at some reviews and forum posts about the Chroma. They do not seem to mention issues with the mouse wheel anymore, so maybe Razer has changed the mechanical part for the better... who knows...