Kenwood chef a901 parts identification needed?

Hi, I would to know what is the zener diode and the small transistor value of the speed controller which had turned unreadable. I had replaced the Triac, X2 capacitors and resistors but not able to control the speed which was running quite fast(constant) with the mechanical screws adjusted but still couldn't get the full speed(slow to fast) control from the turning knob. TIA.