Thanks Kerry, somewhere in the depth under piles of stuff I think i have a replacement Opto Board from a broken up Dracula which i got given to me by a friend over 20 years back, along with all sorts of other parts (ramps, plastics), no idea where it is!. Anyway, it is / was the larger opto board, and in the interim and until I know where it is, I have ordered the main opto board new from an online supplier which should be here in then next 7-10 days from Europe. As I didnt have any 3amp SB (I had used them up ages back and found I needed spares due to this) I haver ordered 6 x 3amp SB and a Clip on Circuit Breaker in both 3amp and 1amp denominations (they were sold out of the rest! of other values I needed).
I think the first course here is to disconnect J118-2 and replace the fuse to ensure the power driver board doesnt blow the fuse with nothing connected.
I am guessing then that J118-2 feeds J3-5 AND J3-2, so disconnecting both and replacing the fuse on J118-2 should keep the fuse live, then if that is stable, when the circuit breaker arrives I can use this to isolate if its "J3-5" or "J3-2" ----- is what I have written seem the correct solution and work flow?