Every wrong polarized cap will make a short, even small ones. ... and if small enough: a very nice BANG!

Capacitors working with negative voltages will often have their positive pin to ground. Check before assuming it's wrong. Martin

Thanks guys Really sorry for my lack of knowledge I'm just trying to learn . I've manged to get a schematic for this power board and indeed the caps are correct as they are . Are there any common fuse blowing issues with this unit I should look into . I have today taken all the mosffets ? off the heat sink and am now waiting for my component analyzer although i think they are ok as the board actually doesnt blow the fuse when the other boards are not plugged into it. the plug that does blow the fuse is the one that goes to the disk drive , Any ideas please ?? thanks again Dave .   ps what is the component that goes from the board where the  audio cables are soldered on to the heat sink (mosfet screw ) googled it but nothing ??