Crown Pulse 2X1100 Supplementary Manual page 8

Diagram 1. View from solder side of PCB.
3. Use a 60V DC bench supply (current limited). Connect it across C75 with +60V to point B and Gnd to point A (see Diagram
2). Fit a switch (switched off) across pins 4 and 5 of OPTO1 (be very careful, as a spark here will kill it).