Hello All,

I need help identifying this diode in the photo attached. It appears to be a MELF, mini-MELF, or DO-213 package. It has a gray polarity band and what looks like the number 3 printed on it. If anyone has seen it before and knows what it is and/or could give some suggestions on identifying it I would greatly appreciate it. I do not have a schematic for it.

Note: It is close to a DC/DC transformer and PWM power supply controller.

Thank you in advance for any help!

 

Can you see any numbers before the 3's?

 

Can you see any numbers before the 3's?

It appears to just be three 3's that circle around the entire diode.

 

It appears to just be three 3's that circle around the entire diode.

No clue what it could be. Don't know why manufacturers choose to be so cryptic. There's plenty of room on MELF diodes to write the full part number like they do on other glass encapsulated diodes (e.g. DO-35, DO-41).

Do you suspect that the diode is defective? You can usually do a dead or alive (DORA) check on a diode in-circuit.

 

Yes, like Dennis said test it first. However, I did find diodes with 333 on them and they were 3.3V zeners.

 

Thank you guys for the input! I have tested it in circuit. It appears to be fine based on the results (forward = ~500 ohms and reverse = OL). But I haven't removed it to test it. I am having a tough time troubleshooting a repair of the PCB its on (I posted it the issue in the technical repair thread) and I can't for the life of me figure out the issue. I just want to make sure I'm not missing anything and if I have to replace parts I want to know what to replace.

 

I just want to make sure I'm not missing anything and if I have to replace parts I want to know what to replace.

We won't be able to help much without a schematic. You can make one by tracing components around anything you suspect.

If you didn't get help in the other thread, it may be because you didn't give sufficient information for any one to try.

 

We won't be able to help much without a schematic. You can make one by tracing components around anything you suspect.

If you didn't get help in the other thread, it may be because you didn't give sufficient information for any one to try.

This piece of equipment doesn’t have the schematic available. I didn’t mention the diode in my other thread because I didn’t think it belonged since it has to do with part identification. But thanks for your help!

 

This piece of equipment doesn’t have the schematic available.

You can trace the board and make one for the areas you want help in understanding function. It's quite a bit more difficult if the board has inner layers. Blind vias would make it even more challenging;.