My mistake - the caps are actually rated at 100V, which makes more sense. What I remembered seeing was a label which happened to be stuck on one of the caps that said 68V on it - but this was actually the nominal PSU output voltage (from 58V transformer, according to what is written on it).

As for pushing the machine hard - this is my "it's just about hanging together still" 3-year-old MDF machine that is normally flat out at 900mm/min. It's currently downrated to about 350mm/min on the temporary 24V PSU. It's a bit of a joke really but there are household jobs on the list that must be seen to be making progress...

I'm suffering from the biblical plague of PSU problems at the moment - my electric razor won't hold charge, my laptop power supply went bang just before Christmas, the router PSU is blowing fuses, and this morning my tablet battery seems to be going on the blink