i see 0.538 and Infinity.

I see in pdf :
Low forward voltage drop

thanks

 

Based on only this information, I'd say it's probably not faulty. I'm making some guesses about what you measured.

You'll get a better answer if you provide more details about what you measured (voltage drop?) and how.

 

the component is not in circuit.

I read psu repair guide and there is something about 2 NPN transistors and check them base diodes. This is one of the two.

 

the component is not in circuit.

I read psu repair guide and there is something about 2 NPN transistors and check them base diodes. This is one of the two.

Even cheap meters have a transistor-check function. If your transistors are out of the board, test them using that. I believe it reports current gain under a certain (and often unrealistic) set of conditions. Much better than simply testing the base.

Or you could even build yourself a little test rig, using the transistor to light up an LED or larger load as appropriate.

 

Hm...
I am talking about diode connected before transistor, that just for protocol.

I measure the item out of circuit in diode testing mode with my middle class dvm

 

The forward drop characteristic of the FR104 diode is below:
If the test current is around a mA, then a forward drop of 0.538V is normal.

 

One other question from diode`s family:
tf12n65
tf12n50

because my old dvm was stolen now i use different and am little confused because the old one had AutoScale for Resistance.
When make short G<>S i measure infinity which is ok but in other direction i see about 520 Ohms. I know it should be low but dont know how low

When make them dewatered i see about half an Ohm which is good