Recognizing Diodes - Troubleshooting Circuit Boards

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naplespete57

naplespete57

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Recognizing Diodes - Troubleshooting Circuit Boards
Got in over my head a wee bit today. Good customer asked me to troubleshoot their welder. After testing the voltage input etc. it was time to call Tech Support.

Among the many things they had me to do was to check the diodes. Well...I am not real sure what a diode looks like! Two decent size circuit boards and I cannot for sure identify the diodes let alone test them! Might have another shot at it again tomorrow.

These diodes are part of the rectifier circuit.

Any tips on identifying? Capacitors are rated in farads and would me labeled right? Diodes?

On a side note how many diodes would be in a three phase rectifier? I am guessing 6.
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In my personal opinion, if you do not know what you are troubleshooting, let alone do not know what the components on the circuit board look like or how to test them, then you should not attempt to troubleshoot it at all.
 
eric7379 said:
In my personal opinion, if you do not know what you are troubleshooting, let alone do not know what the components on the circuit board look like or how to test them, then you should not attempt to troubleshoot it at all.
Click to expand...


I didn't know how to walk when I first tried.

If the link below works you should be able to see a "three-phase bridge diode" module I searched for on Newark.com. Almost all vom of any quality will have a diode test setting. Get the manual out & have at it. Make sure the power is off.

http://www.farnell.com/datasheets/104029.pdf
 
Small electronic diodes are usually look like they have a glass case, and they have a black band around one side to indicate the cathode.

Larger electronic diodes are usually black with a white band to indicate the cathode. They may have a number printed on them like 1N4001. ( I was once young enough to read that small print :) ).

Larger power diodes may be a button type that is directly attached to a metal plate that acts both as a contact, and a heat sink.

Even larger diodes are on a threaded stud that screws directly into the connnection. They have a wire lead comming out of the top. The threaded stud allows even more heat transfer to allow the diode to dissipate more power.

There are probably more types that I'm not familiar with.

Steve
 
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