Do you have schematics ?
You will need a slo blo. Jaycar or any electronic store should stock them, or buy from us here -
https://www.rtbb.com.au/product/mdl-1-1-4-slow-blow-fuses/Don't waste time or $ until you use the correct slo blo... Then try the below ;
1/4A SB Fuse on the fuse board is for the +69 V which goes to the Power Supply. You can remove the input connector to the power board and then test for the fuse. That will eliminate the Bridge rectifier on the fuse board.
More likely, it will be a display, so you could try disconnecting all the displays and add one at a time until the fuse blows. NOTE - DO NOT disconnect a display while power is on.
Report back..
