quickest/easiest way to test zeners?

[Alex R]

Any ideas?

[PRNDL]

Zener diodes can be tested for open and short with an ohmmeter the same way that you test regular diodes. Testing for operating voltage needs to be done in a circuit.

One of my first repairs as a tech was a MuTron power supply that used two 9 volt zeners. If I recall correctly, testing it in the circuit showed some unusual readings, but out of the circuit showed it was open.

The same customer also brought in a MuTron Phasor, which had problems with the LFO. It's one of the coolest tones ever!

[Amp Kat]

If it's a zener used for a regulator simply check for it's zener voltage. If it's say a 9 volt zener from ground reference check for 9 volts. If you get less than 9 volts are even zero it's most likely bad.

[Enzo]

Yep.

First, they are diodes after all, so they should test OK forward and open backwards on a meter like any other. If a 1N4007 shows maybe .470 volt on a diode test expect a zener to read a little higher, like .6 or .7v. But still acting like a diode. This sorts out the shorted and open ones. Then like KB and PRNDL said, they must be in a live circuit to test their zener voltages.

If you have a bunch and wanted to make sure they are OK, you could rig up a tester easily enough. Start with a voltage source, either a bench supply or steal some voltage from an existing product. COnnect it to the zener to reverse bias the zener, and IMPORTANT you need a resistor in series to limit current.

SInce zeners require a certain minimal current to "zene," make the resistor a pot. Now dial down until the thing turns on and then the voltage should be pretty stable across the part. Don't turn the pot down too low and overcirrent the zener.

[Alex R]

Thanks all - really helpful as always.