Check connector CN1 on power supply.  Make sure no burnt pins or cold joints.

Test for 68 volts DC at Diode D5, banded side positive, negative to ground.

If no/low volts, test/replace the following components in order.
Resistors
R8 - 47K, R11 - 330K, R12 - 1.5K and R15 -500R.

Diodes
D5 - IN4004, D6 - IN5228(3.9v zener) and D9 - IN4760(68v zener)

Transistors
TR1 - MPSA92 and TR3 - MJE340

Also capacitor C10 is important for 68 volts.

The above components comprise the entire 68 volt section of the power supply board.