Ball size: 21/4" (57.03mm)
Typically, industrial-grade trackballs are far superior to the consumer products by terms of advanced technology, quality of parts etc. This one seems to be rare exception: despite high asked price, the device is incredibly primitive and poorly designed.
Ball support is made in form of separate plastic ring with 6 steel balls of approximately 2mm diameter. The ring is freely laying in the case, having significant free play. In addition, due to small diameter the ring is contacting just very bottom of ball, allowing it to rock sideways. The sample I've got have remarkable wear: steel balls developed visible flat spots on them:
The sensors are of unusual design: rollers with foam rings are mounted directly on sensor enclosures. Bronze bushings are glued to the sensor's plastic casing. Lubricating oil is dried and/or contaminated, so they aren't spinning freely. Tried to dissolve the oil with WD40; one roller became free, but second isn't: foam ring rotates by itself, while roller is still stuck. For full restoration, it's needed to destroy glue blobs for disassembling, and replace foam rings with new ones - but I don't think it's worth it.
After time, the foam started to deteriorate: internals are full of debris. It's sticky, so blowing with compressed air can't remove them. The encoder discs, made by photo technology, are also contaminated. Interesting detail is, instead of common dual photosensors there's two separate concentric zones to provide 90° signal shift. Sensors marked OPB3758A made by Optec. Datasheet for this particular model seems to be unavailable, but it's apparently similar to their OPBxxx series. Specified resolution is 375 PPR (53 CPI).
As this model have quadrature signal output, there's practically no electronic components on PCB except for couple of resistors and capacitors, along with 4 potentiometers to adjust sensor LEDs current. Connector is DB-15:
BEI product specification sheet:
https://trackballs.eu/media/BEI/TBS225/ ... cSheet.pdf
To summarize, the movement of the ball is hard with uneven resistance, and accompanied with significant wobbling due to the design. In fact, there's nothing to fix or improve: entire construction is poor. In general, this is probably most bad trackball I've ever encountered. Resume: do not buy, unless you're looking for ridiculously expensive source of spare ball and encoder discs.
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