Metz camera flash repair

[trisa25]

Hello,
my dad was using a Metz camera flash and once it just poped, screen went black and nothing happened and he just took the batteries out. When I opened it I found an blown smd diode and replaced it with 1n4007, but after that when I tried contiunity across battery terminals it was shorted and I also found out that transformer mos-fet (custom one with core on the pcb and metal shielding) was shorted and first replaced it with buz11. It worked, but buz11 got very hot (transformer is drawing less than 5A at arround 6V). then I switched to irl3803 (170A hex-fet), but ist sill gets very hot and charges capacitor very slow. Is the problem frequency of DC-DC boost converter or something else?
Thanks for answer,
trisa25