The active area now faces the emitter
If your trackball has a failed scroll ring, tweaking its alignment certainly can’t hurt.
There’s very little IR hitting the detector …
It’s an optical device, so I suspected it had ingested a wad of fuzz that blocked the beam path.
You need not only the proper plastic shell, but also the pins and the crimper
Tried it on three different PCs and five different operating systems with the same result: the ring stayed dead.
And, for whatever reason, the scroll ring now works perfectly