its about that http://www.alldatasheet.com/datasheet-pdf/pdf/53235/FAIRCHILD/5H0165R.html

can i test it out of circuit and of course how ?

i think that the way is in circuit with DVM and osciloscope but want a opinion. Is it dangerous for my scope to analyze that scheme?

thanks

// i desolder the heat sink "number 1" from computer PSU and it`s on it.

 

is pin 4 fb feedback ?

 

What characteristic are you trying to test? Fairchild has a design guide if that helps:

https://www.mouser.com/catalog/supplier/library/pdf/FairchildPowerswitch.pdf

I know on this occasion this datasheet doesn't including any test circuit (sometimes the manufacturers include a simple test circuit or design note), but if you post what you want to test for (i.e. switching time, RDS resistance etc) one can determine what the best test circuit to use with this component.

 

i am learning to repair computer power supply units.
I am reading one guide which is maybe for earlier standart PSUs.
In it is written "check the key transistors" but on the first heatsink i see only one MOSFET transistor and this IC. On second i see 3 Diodes and they are ok.