Just in case anyone is wondering, yes, it is possible to reflow a whole board as a last ditch attempt for boards where the source of the fault is extremely tricksy.

 I don't have a proper oven which can cope with the maaaaaasive thermal mass of all of the heatsinks, so this puts the board *way* outside of the reflow parameters (it takes about 15 minutes to get up to reflow).

... Take off the electrolytics and the power connectors, clean board (I use isopropyl dip), apply thinned down flux to the topside only, ensure that you are heating on a solid surface.

On a completely unrelated note, the black thermal adhesive copes remarkably well with heat. The white stuff... Not so much. Completely degrades and a slight touch will knock off the heatsink. So, I now have a completely bare of heatsinks board and am desperately trying to think of a way to properly heatsink it. I may just end up oil bathing the damn thing (it's a 54 chip board, so there are no non-SMD electrolytics).

If you leave the connectors on, they will survive (foil wrapped) but look unhealthily yellowed. Subtext: Don't do this, there are *far* better ways to spend your money and time.