Sterling Power marine 12V 20A battery charger - blows fuse

[Lomax]

I'm trying to repair a Sterling Power Products Pro Charge CE1220 marine battery charger for a friend of mine. From what I've seen these go for £60+ used, and an equivalent new model would cost over £300, so although it's pretty ugly,  and clearly has seen better days, I reckon it's worth a shot. Having overcome my disgust of the horrible exterior, I was pleasantly surprised by the tidy interior, and that the fault was immediately apparent; one of the two main caps had burst fairly violently. So I ordered a new pair of caps, and after a considerable struggle with getting the PCB removed (the mechanical design is incredibly stupid) replaced the caps and re-assembled the unit, thinking this would have fixed it. Alas, what was previously a completely dead charger now instantly blows the 3A mains fuse when plugged in. So I'm going to have to take the damn thing apart again and perform further checks. Since it's such a bastard to disassemble, I thought I'd check with the forum if anyone has any suggestions which parts are likely culprits? I'm thinking the rectifier bridge, possibly one of the MOSFETs? Any suggestions and advice appreciated!