SMD diode testing help required for 10-25 N4

[Mithun_K_Das]

I have a unknown circuit at my workshop few days ago. Reported as diodes are faulty. I found some diodes named: '10-24 N4'. Found no mark as the through hole diodes have. Actually I'm not familiar with this device. I checked with Diode tester(with Sanwa CD-800A). some diodes showing around 0.5V, only two is showing 0.13V both in reverse and forward. I should test it removing from the ckt. But there is no mark for Anode/Cathode.

Can anyone tell me how to test this?

 

[barry]

How do you know they're diodes? I can tell you how to test it, but if you don't know which end is which, that's not going to be too much help.

 

[Mithun_K_Das]

at the PCB, a mark is written, D6.1, & D6.2... like this. That means its a diode. And the other diodes have the mark at the cathode. only these 2 have no mark. But as all of them are marked as like Dx.1, Dy.1 etc so I think its a diode.

 

[barry]

Ok, assuming they ARE normal diodes and not DIACs or transorbs or zeners or tunnel diodes or some other oddball, if you've got one that tests good (.6V forward, no conduction reverse) that should enable you to identify the cathode. Then you can test the others and know how to mount their replacements. But you still won't know what kind of diodes they are unless you can find that part number. You don't say what kind of circuit this is: power supply? RF amplifier??

 

[FANT]

I have found some zener with very low voltage ( say under 2 volt ) trat show a drop on both side, on one side 0,6 V or lower and on the other side the zener voltage ( say 1,8 V, the one I have tested ), but never 0,13 V on a silicon diode.
May be it is a schottky diode ?
If you test it with a low current, the voltage drop is in that range, it is strange that it is on both side.
But isn't that the two diodes are in antiparallel ?

Mandi

 

[Mithun_K_Das]

Ok, assuming they ARE normal diodes and not DIACs or transorbs or zeners or tunnel diodes or some other oddball, if you've got one that tests good (.6V forward, no conduction reverse) that should enable you to identify the cathode. Then you can test the others and know how to mount their replacements. But you still won't know what kind of diodes they are unless you can find that part number. You don't say what kind of circuit this is: power supply? RF amplifier??

Its a control card of PLC, came from a Textile Industry. @ barry.

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I have found some zener with very low voltage ( say under 2 volt ) trat show a drop on both side, on one side 0,6 V or lower and on the other side the zener voltage ( say 1,8 V, the one I have tested ), but never 0,13 V on a silicon diode.
May be it is a schottky diode ?
If you test it with a low current, the voltage drop is in that range, it is strange that it is on both side.
But isn't that the two diodes are in antiparallel ?

Mandi

No FANT, they are not connected anti parallel. I wanted to remove the device to check it, but the PCB is multi layered, and the diodes are soldered to the middle layer. I'm afraid to replace with the equivalent one.