Yamaha P-350 turntable running fast

[henning1]

Hello, my Yamaha P-350 runs too fast. It is not a matter of a little too fast but rather some 50% both for 33 and 45 rpm. I have the service manual. But what might possible cause this fault, please?
Kind regards

 

[tnsilver]

By the schematics - roughly from best to worst case:

• check PS capacitor C202, replace if needed. Make sure you have 13.7VDC on the positive rail to the motor after the rectifier bridge.
• if you find a 4.7uF capacitor across the motor - verify / replace
  
• verify the values of resistors R201/R202. Adjust speed control trimmers 201 (33) 202 (45)
• check / replace electrolytics C2/C10 and verify resistors R1/R2/R3
• verify the small value capacitors around BA808 and replace the IC if needed
• faulty built-in motor tacho. service / replace the motor.

 

[restorer-john]

By the schematics - roughly from best to worst case:

• check PS capacitor C202, replace if needed. Make sure you have 13.7VDC on the positive rail to the motor after the rectifier bridge.
• if you find a 4.7uF capacitor across the motor - verify / replace
  
• verify the values of resistors R201/R202. Adjust speed control trimmers 201 (33) 202 (45)
• check / replace electrolytics C2/C10 and verify resistors R1/R2/R3
• verify the small value capacitors around BA808 and replace the IC if needed
• faulty built-in motor tacho. service / replace the motor.

@tnsilver pretty much covers it well, although I'd probably start at the motor itself in this case and the 4.7uF cap. The IC works on back EMF and it's a brushed motor, so a dirty commutator and/or brushes and it's going to be all over the place.