Have checked all the fuses and there are some that are amiss.  There are quite a few that are not marked 250v so i assume these are 12v as most of them are much higher amperage than specified.

On the power supply board
F1 is 10A 12v  should be            3/8 A 250v
F2 and F3 are 10a 12v should be 1/8 250v

On Aux Power driver board

F4 is 5A 250 should be 2 1/2A 250
F5 is 15A 12v should be 2a 250
F6 is 30A 12v should be 2a 250
F7 is 15a 12v should be 4a 250

On Interconnect board

F2 is 5A 12v should be 5a 250

Then there is another fuse that is the "+18vdc Lamp Ckt/ Lwr Rt Backbox Fuse Holder" which should be 8A 32V - it is an 8A but 250v and is a strange ceramic looking centre bit (instead of glass) and when tested on the multimeter - there is no continuity but a resistance of around 320 k ohm. (see pic)

So i don't know if this is a potential culprit, but i will certainly grab the correct other fuses for future testing.