here is the latest.
board measures 8cm x 10cm. its designed it to fit in a case with a vertical 3pole 3way rotary switch. there is an added a facility for two LED's which switch between 33/45. case will also house the transformer and should be 10cmW 5cmH x 20cmL. so pretty dinky
there is a full rectified dual linear power supply with a ground plane which helps with unwanted noise entering the system. i have also added two small caps on the opamp to keep it from oscillating if needed which i doubt but they are there anyway.
all traces are a direct replacement of the originals as we know the boards work.
i have tracked down some tacho motors that are used in tape decks so should be of decent quality. these have 4 wires just like the original motors. they are bigger but fairly short 37mm wide x 50mm tall. dont know the speed till they get here then i can get pullys made for them.
i'm going to send off and get a small batch of boards made up and build one for testing with the motors.
if it works which i see no reason for it not too i think this would make a superb replacement for LPT and PTTOO tables which by chance i just happen to have
now if someone had an anniversary board knocking about that i could take a look at i could update these to anni spec
one more thing. i have been looking into using a optical sensor for the tacho and so far it looks doable. i have also sussed out how to get the markings on the platter, use heat transfer paper and iron them on like making pcb's. if not then its 0.25mm brass acid etched out.
back emf is going to take a while and i might not even bother depending on how well this works.