Transformer voltage on Clark CW 11T spot welder timer pcb?

My old spot welder stopped working so i opened it up and found that there was no resistance on the primary side of my step down transformer (on the timer PCB). Unfortunately there are no detail on the transformer.

How can I tell what the secondary voltage should be?

Is it possible to working it out form the capacitors or integrated circuits?

There is an unused connection on the primary side of the transformer which has resistance, can I power this up and check the secondary voltage???

how critical is the secondary voltage?

FYI I'm in the UK and primary voltage is 240.

Thanks in advance