VU+ Duo PSU Problems, 12v Supply drops below 10v when HDD spins up

Hello all, As the thread title states, I have a VU+ Duo here from a friend, I know its a genuine one too, Its having some power issues, It would not boot at all due to defective PSU board, I have got a replacement from ebay and the box now boots but has some problems using the HDD due to Low voltage on the 12v rail when load is applied, I have tested the box using my PSU from my own duo and all is working fine so its defo the power board, My guess is a cap or something but which one, I can solder so swapping it is no bother, Plus i have the old board so i have the parts needed hopefully, Symptoms of old board is no lights at all, no DC voltage on it at all, Im not an electronics engineer but have a basic understanding of general electric components and i can solder prety well