I've just given the MOSFETS a good drink of acetone to remove the 'tropicalising'. My googling doesn't reveal anything for GV5H1D & i sure do not recognize the maker's logo. The "JSH" axial electros are 35V 125 degree at the input while the three at the output end they are 6.3V same maker. The board runs fairly screaming hot with same-sized alloy plate attached that's then clamped to a more substantial one.