Siemens 24V-20A Power Supply repairing need help!

[phamhuuthien]

Hi everyone,
Currently, I am repairing a Power Supply 24V 20A of Siement, I have a problem with 2 power BJT and a Mosfet. The BJT is BU508 and Mosfet is BUK543-50B.
The Mosfet is switching on for the BJTs, and the BJTs is switching on for tranformer. They are broken, I have replaced the Mosfet is IRFZ44 (I can't buy a BUK543-50B at my local) and the BJT is BU508. After replace, I powered on my Power Supply then the BJT is broken again and a zener. The IC drive for the Mosfet is UC3843.
I query that I replaced Mosfet not right. Can everyone tell me that the Mosfet is right or don't? If don't right, Can tell me the equivalent Mosfet and BJT? Again, I can't buy a BUK543-50B and a BU508 at my local.
Thank you so much.

 

[pradeep.g.belchada]

check the o/p of smps diode may be short

 

[phamhuuthien]

check the o/p of smps diode may be short

Thank you!
could you show to me the o/p of smps diode that you tell? I don't know o/p and smps word.
again, thank you.

 

[pradeep.g.belchada]

check byw 99 diode, and some uf5408 type diode, check output side of smps transformer where you get dc 24volt