The general idea is to gut an old Dell Optiplex GX270 and stuff the high-voltage parts of the sewing machine controller inside a well constructed and solidly grounded metal shield inside a not-too-ugly plastic box. It’d be nice to reuse the power control button and status LEDs on the front panel…
The few parts on the front of the through-hole board:

The copper side, with annotations:

The red tracer on the ribbon cable goes to Pin 1, which is a blind key on the PCB.
The LEDs do not have ballast resistors, so those must go on a circuit board somewhere else.
The connections:
16 | 14 | 12 | 10 | 8 | 6 | 4 | 2 |
Gnd | nc | nc | nc | nc | HD+ | HD- | Button+ |
Gnd | nc | Gnd | Pwr Y+ | Gnd | Pwr G+ | Gnd | Key |
15 | 13 | 11 | 9 | 7 | 5 | 3 | 1 |