How to put a new sensor into an old mouse?

[Plautus]

I have a Logitech m720. It's a business mouse.
Where can I Buy a sensor and how to put it in?

[suicidal_orange]

If the sensor has died and you want to replace it look on the part to find a manufacturer and, hopefully, a part number, then you can look for datasheets and possible compatible upgraded versions.

If you want to upgrade it to a higher DPI you can't as the firmware wouldn't be compatible.  You could make a new circuit board that fits in the case if you like the shape and weight, there have been a few attempts at DIY mice so you would want to look at those to see what's involved.

[Findecanor]

Replacing the sensor with a better model is not something you just do. I don't think it would be worth it.
Maybe it would be possible if the old and new sensor chips are in the same series with the same pinout and interface protocol - but you would have to dive deep into datasheets to find that out.

You could perhaps buy a new mouse with the sensor you want and transplant it into your old mouse. You would probably have to mod both the old casing and new circuit board to make it fit — If it would fit at all.
But yes, there are a few people who have done this - especially putting new innards from small optical mice into classic vintage mice.

Or you learn circuit design and programming, and make your own innards. But it would be a lot to learn, and not cheap.
There are small microcontroller boards and mouse sensor breakout boards out there, which you could connect with wires but those would probably still be bigger than the old circuits, especially with all the wire connections.
Or design your own circuit board, and have it made with a new sensor, new microcontroller and your own modified firmware to go with it.

[Leslieann]

You might get away with it if it was a cheap mouse, but I doubt you will get away with it on a Logitech.
I can't say how much (especially on an office grade mouse), but they do take the time to tune tracking to the lens and sensor.