Film-Tech Forum ARCHIVE: Open diode question

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Posted by Richard May (Member # 2627) on 06-24-2011, 12:55 PM:

I've had this happen only a few times before. I have an open diode but the lamp lights. Amperage drops to about 25 amps and the volts go over 100. Why is that?

Posted by Randy Stankey (Member # 64) on 06-24-2011, 03:24 PM:

Ohm's Law.

As current goes down, voltage must increase. It always follows the proportion E=I*R where "E" is voltage, "I" is current measured in amps and "R" is resistance measured in ohms.

When a diode dies, you lose one leg of your transformer. It can no longer provide the current that it should. The voltage will increase in response.