Is this diode faulty? fr104

wayneh

Joined Sep 9, 2010
17,467
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.
 

Thread Starter

UnnamedUser159

Joined May 3, 2016
501
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.
 

wayneh

Joined Sep 9, 2010
17,467
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.
 

Thread Starter

UnnamedUser159

Joined May 3, 2016
501
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 ;)
 

crutschow

Joined Mar 14, 2008
33,337
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.

upload_2017-9-7_13-32-43.png
 

Thread Starter

UnnamedUser159

Joined May 3, 2016
501
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
 
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