The whole assembly (circuits and the mechanical bits) forms a PPL (Phase Locked Loop). This requires two 'inputs' to function.
I have measured the incoming synch pulses to the motor control circuit, and they are rock-solid 12V at 61ms wide.
This I assume is from the disc sensor, the IR pair. The other input, the reference, is the signal that comes from the signal source, the CD player. If this is fed into the motor control circuit after a pot it will lose lock at some point as you turn down the gain.
Without having complete details of your arrangement it's hard to offer much more help. But I would check with a scope both inputs to the 4046 on pins 3 and 14. Quoting the STM datasheet for the device...
The phase-comparator signal input (terminal 14) can be direct-coupled provided the signal swing is within CMOS logic levels.......for smaller swings the signal must be capacitively coupled......
So pin 14 should have a logic level input signal, 0V to +12V (I assume you're using 12V). OR have a capacitor on its input for smaller signals, but here they still need to be more than 1Vp/p for reliable operation.
Pin 3 is a logic input and the signal here should go from 0V to +12V, no ifs or buts.
Steve A.
I attach two datasheets for the device for those that don't have them.
I'm also a little concerned as to your measurement of 61mS...do you really mean milliseconds (mS) or microseconds (uS)? Can this board support Greek characters so often used in electronics and mathematics?