Hi everyone,

I am working on a power supply that has recently suffered a mosfet going pop.

Underneath it, I found this diode to be shorted in both directions. It seems to have a silver and green band. The silver may indicate polarity, I am not sure. I found another exact match of this on the board, and measuring this in diode mode yields a measure of 0.34v. However, I have no idea how to cross-reference this. If anyone has any pointers it would be much appreciated.

Thank you very much!

Ryan

 

The major specifications for a diode are forward current rating and reverse voltage withstanding.After that come switching time and forward voltage drop at rated current. There are a lot of other parameters that also matter in some applications.
Was the power supply a switch-mode supply, or did it have a big heavy transformer?

 

The major specifications for a diode are forward current rating and reverse voltage withstanding.After that come switching time and forward voltage drop at rated current. There are a lot of other parameters that also matter in some applications.
Was the power supply a switch-mode supply, or did it have a big heavy transformer?

Hi there, thank you very much for the reply.

To be perfectly honest, I am not sure, I am not familiar. It does have transformers, but not one huge one. It is a power supply out of a vintage IBM P75.

Thank you again for the help!

 

OK, and thanks for mentioning the application.Probably there are a few individuals who have actual experience with that device and so be able to provide advice.
But as it is a computer power supply it is most probably a switch-mode system, meaning that most components performance is rather critical.
And the bad news is that parts seldom fail for no reason, and so quite likely that the failed transistor failed because some other part failed, which is not a visible sort of failure.

 

Post a photo that shows the full view of the power supply.

 

If the specifications of that failed supply are known it is quite likely that it could be replaced by a much more current supply in a smaller package.