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Main => Monitor/Video Forum => Topic started by: kardenm on April 14, 2010, 09:22:06 am

Title: zener diodes
Post by: kardenm on April 14, 2010, 09:22:06 am

Can anyone tell me? Is there a way to test (check) a Zener diode??

Title: Re: zener diodes
Post by: MonMotha on April 14, 2010, 09:41:42 am

The "diode check" setting on most digital meters can usually be used.  Should read ~0.7V with the red lead on the anode and black lead on the cathode, and it should read approximately the rated zener voltage (maybe a little lower) the other way.

Title: Re: zener diodes
Post by: kardenm on April 14, 2010, 09:53:08 am

Thanks. How can I tell what the rated zener voltage should be? Which end is cathode or anode?  Mine tests 0.00 volts in both direction on the diode check setting.  I guess that means it is bad??

Title: Re: zener diodes
Post by: kardenm on April 14, 2010, 10:02:38 am

It's a "7.5BM" (from schematic), a 7.5v zener diode. I guess that means it should reab 7.5v in the other direction.?

Title: Re: zener diodes
Post by: MonMotha on April 14, 2010, 10:04:59 am

Zener voltage rating is the primary rating of the part.  "7.5BM" sounds like probably a 7.5V zener, yes.  The end with the stripe is the cathode.

If you're reading 0V in both directions, it's probably failed shorted.

Title: Re: zener diodes
Post by: kardenm on April 14, 2010, 10:11:44 am

Thank you MonMotha.