Hello I'm new to this forum.. I'm in need of desperate help! Posted is a schematic of a P.W.M circuit that is powered by a 12V DC PS. As the pot. is turned from 0-50 the motor is supposed to spin CW, and 50-100% CCW. This circuit is not working! For the transistors, instead of the ones in the schematic i have replaced them with the NPN CB547B and the PNP C557B Am I using the wrong transistors? Am I missing anything? I am not allowed to use another 555 timer. I only have to use the H bridge format.