Showing stage 1, generic external power supply mod, where an external 21V DC supply is connected directly to the motor PCB.  Note the PCB/chassis grounding post is the bottom-left one, and the DC cable is soldered to a point underneath the board (entailing removing the motor bearing assembly with the three hex bolts).

Showing the Jaeger connector used to connect the other end of the cable to my Paul Hynes SR7-21EHD external power supply.

Stage 2 involves feeding an external 27V DC supply (I adjusted my SR7 to provide 27V)  into an internal Paul Hynes TDR-21 dual 21V regulator, one rail for the speed regulation electronics and the other for the motor drive.

Testing the supply rails: 27V in, 21V out.

Stage 3 takes the 21V rail intended for the speed regulation electronics and further regulates it to provide 5V and 9V DC rails using small Paul Hynes regulation modules.  Several track cuts need to be made to the board, again entailing removing it from the deck.

The finished deck shows no signs of the work done 'under the bonnet', except that perceived speed and pitch stability are so tightly controlled that you are left with only hearing any remaining effects of off-centre holes.

Parts List

•Paul Hynes SR7EHD-27 external 1st stage 27V power supply
•Paul Hynes TDR-21 internal 2nd stage twin 21V regulator
•Paul Hynes S1709v4LN internal 3rd stage 9V regulator
•Paul Hynes Z1705LN internal 3rd stage 5V regulator
•Paul Hynes Clearsilver XL cable & Jaeger connector

You don't need to use PH regulators, but they are perfect for the job and fit the available cavities.