Ok, it looks like a variation of a washing machine speed control, most probably using a TDA1085C (16 pin chip) or one of the chips in that range. Things to check are the voltage across the 100uF capacitor sitting vertical right in the middle of the board in front of the Tacho connector. You should have somewhere around 14-16 Volts across it, if not, suspects would be the transformer, or the two square yellow capacitors at the corner of the board, or the diode in the middle of the two resistors where it says D21 or one or more of the diodes beside the yellow capacitors etc.
If the 15V is missing, lift one end of the diode above where it says D21 and try soldering a couple of wires to the pcb at the 100uF capacitor and inject a maximum of 15V, watch your polarity and voltage as a mistake here will blow the control chip, also remember to use an isolated supply, as one side of this supply will be at mains potential when connected. If the speed control runs ok, the problem lies with the power supply built around the transformer/ yellow capacitors. diodes and the scr's etc, if the speed control doesn't run with an external supply, then check the opto couplers and the 820K resistors, one of which is above the triac on the heatsink and the other in front of the optocouplers.
Obviously quickly check all the other diodes, but I think they are unlikely to be faulty.
It could be one of the small capacitors around pins 4-7 but again, without testing them there's no way to be sure.
rgds