Chasing the Sony CX20084 speed chip for D6C walkman

One thing that catches my attention is how this circuit is powered (missed this detail in LeKos schematic, but see it is there too): it's using the +11.2V rail from the DC-DC convertor and regulate it down to 5V.
The motor draws ~100mA with load, not sure if that DC-DC can actually supply that much extra current (without significant ripple) since it wasn't designed to power the servo or the motor, but just audio circuitry.

I think it's a better idea to power it directly from the 6V rail with some protection which has to be low-dropout given minimum supply voltage of BA6301 is 4.5V.

As for the FF/REW auto-off, that has to remain.

Wonder if the other Chinese replacement (https://www.goofish.com/item?&id=766454209480) is also based on the BA6301.
In this case only the IC is powered through a regulator from the 11V rail, not the motor.

 

I feel the same, I have already written off this board as a lab experiment in what NOT to do. Last evening I modified it heavily by connecting both motor and FG directly (contrary to Chinese instructions) and FG noise went way down. I also twisted the FG wires like a twisted pair to maybe reduce some motor noise. Finally I installed a (larger, throughole but more suitable) transistor and to suspend the motor from the 6V rail. I think LeKos forgot how weak the 10.8V rail is AND the motor noise you get in audio as well. He has a second problem, tying pin 5 of the CX20084 (or pad 5 with that chip gone) directly to 5V. Not sure how that works but it certainly exceeds the 3.15V(brown PCB) 4V(Green PCB) Electrolytic rating on that pin. My Chinese board has a trimmer that biases pad 5 between 0-5V (factory set to 3.65V). It’s totally unstable however. Sony indicates that pin as 1.65V. Any opinions on how to determine that?

I think the other Chinese board looks suspiciously like the Korhonen board for early brown PCB units only, where you must remove the components around the CX20084 as well to attach the board to the battery solder tabs. I think the solution (for later units anyway) will be a more rectangular board that fits in the bottom of the cabinet (top of the unit in use) beneath the DC-DC converter. At least on the D6C I have there is plenty of room down there.