L98FIERO
Ref. Tamagawa AU5589-6590-1382.. it is the spindle magsensor amplifier PCB & feeds amplified signals into the spindle drive.
It requires +/15V power to operate. The outputs PA & PB are essentially sine waves and the frequency depends on the spindle RPM. For every 100RPM, my scope measured about 850Hz.The output voltage is seen between (+/- 1.5 to 2Vpeak) or 3Vp-p to 4Vp-p. Hope these helps.