Hi John 😅 👍Its not a voltage mumultiplier mate, they a MOVs not caps,and theres no diodes, they are there to protect the pulse transformer if the fence were to be struck by lightning.. The way it works is the first side is a high frequency inverter it takes the low voltage 15v DC input and steps it up to charge the larger capacitor which is then repeatedly dumped into the primary side of the iron high voltage step up pulse transformer the secondary voltage form the pulse transformer makes its way across to the outputs, the string of resistors next to the movs is a voltage divider so you can have a choice of output voltages on the binding posts on the front panel, the optical bridge you mentioned is called a high voltage opto coupler it consists of a 950nm infrared led at one end and a photo transistor at the other and as you correctly assumed its feedback to monitor the output.. 👍 ps I think your right about the smps brick probably hv back spikes For further reference you could put a ferrite core on the DC leads and a 15v zener clamp 2200uf 25v cap and and parallel 220nf cap all across the input to the board.. It would be better to use a dumb supply tbf just a transformer rectifier and smoothing cap, maybe an old car battery charger with an extra filter cap etc.👍
