Patching up a Mega Watt S700-12.

[MKwrench]

My "new to me" power supply suddenly and violently poped it's fuse, I'm assumung from some sort of surge, because the same setup operates just fine on another power supply. When the fuse popped it created a bright flash like a quick welding arc, so its a good short. I just began testing across "Line" and "Neutral" until I came to the 2 switching fets in the back, they both tested as resistors.
When I replace these is there anything else I should look for, or just replace for peace of mind?
These are obsolete and Google has recomended something different each time I asked... LOL
Here are some pics of suspect parts removed for testing.

 

[nomadradio]

When I replace these is there anything else I should look for,

It's all about the specs. If a replacement's data looks similar the failed one, you're good to go. Odds are you'll find specs at alldatasheet.com.

73

 

[brandon7861]

mouser and digikey both have the datasheet, both show it as obsolete, and both offer the ability to search for similar parts. Digikey will suggest parts directly and mouser wants you to check the parameters you want to match before suggesting parts. The part number of these mosfets tells some too (if you ever can't find the datasheet). 40N50. 40 is the current rating, N is the mosfet type and 50 (*100) is the voltage rating. So 40N50 is a 40A 500V N-channel mosfet.

https://www.onsemi.com/pdf/datasheet/fql40n50-d.pdf

IXFK80N50P may be an option.

 

[Lost Ram]

The owner of mega watt is a pretty nice guy. I have had some fail and asked about sending them back but he just offers me a great deal on a new one. I am not sure if he even repairs them or not. If he does he might have some suggestions for you.

 

[Eldorado828]

Hopefully i don't jinx myself, but I've been running one on the work bench for at least 10 years now and it's still just going. It's on a lot and I mean a whole lot unless it's at night or I'm not in the garage. Good supplies no doubt and especially for the price range.

 

[MKwrench]

Thanks for the input guys. I wish I knew what happened to cause it to suddenly Poof out. It was working fine, powering an NPCd PC122 and a DX250 on a dummy load to teast the pairing. I continued testing on my 36a Alinco P/S.
I might try a set of IXFK44N50s, they're real close in spec. I also read that I should replace the bias components, and that the 44N will switch faster because of a difference in gate capacitance and threshold voltage to possibly cause noise in the system. I guess the fix is to add resistance at the gate to slow the switching frequency if needed.
They're $16 a pop though, so I want to be careful with the repair.