Im gonna ask if zener diode BZX55C24 can be replaced by IN4749 ?

Both of them are 24 Volts but I dont really know if they are the same because they have same volts.

I just buy this diode here at my local electronics store, I did not put any information only BZX55C24 Zener Diode and they confuse what is the number of that Diode and they said to me confusingly it was 24 Volts? and they gave me IN4749 Zener Diode.

That BZX55C24 Diode was short-circuit and was connected to the gate of WFF3N80 which also have open-circuit gate, these are found when I troubleshoot my Power Supply Unit of computer.

Please help...

 

The 1N4749 has an absolute maximum rating of 1W while the BZX55C24 has a 0.5W maximum rating.

Since you are using the higher rated component, you should have no concerns with the component selection.

Of course simply replacing this component may not fix the power supply problem.

 

Yeah man, I replace BZX55C24 Zener Diode and WFF3N80 MOSFET, still the PSU did not work. The PSU's fan may turn on in less than a seconds and turn off...

Any idea how to fix this?

 

MOSFET gates will measure open, unless they somehow become shorted. The gate is insulated from the drain and source terminals.

Can't seem to find a datasheet for a WFF3N80. Are you sure that's the correct part number?

 

Yeah man, I replace BZX55C24 Zener Diode and WFF3N80 MOSFET, still the PSU did not work. The PSU's fan may turn on in less than a seconds and turn off...

Any idea how to fix this?

You are in luck.

If the fan runs for a brief moment, then most likely your power supply is now working. It is producing 12V to run your fan. It just shutoff again because it has sensed there is no loading on its output.

Have you tried to connect it back to the computer board or whatever loading to test it?