Microwave oven diode testing

[JHNC]

Testing a CL04-12 diode from a microwave oven. Tested using a Peak DCA55 & a Fluke 87 DMM. Tests as bad / open on both devices. Then I read on a post that these type high voltage diodes will read as shorted on a DMM, such as my fluke and that you need to test them with a 9 volt battery [not sure what they meant as my meter uses a 9V battery]. While peak lists no exception for HV diode testing and many DMMs have a built in diode test function setting, I want to know:
1. Can you accurately test a 12 kV 0.45 Amp diode on a DMM using either the
    Ohms scale or the diode test setting?
2.  If not, how do I correctly test it for open or short on an HV diode?

[coromonadalix]

no   

normally an microwave diode need many volts to test it, i think around 7 -8 volts should be sufficient

search google for microwave diode testing ...

[Andy Watson]

.... that these type high voltage diodes will read as shorted on a DMM, ...

I think you mean open-circuit. If the diode tests as shorted on DMM then it is definitely dead.

such as my fluke and that you need to test them with a 9 volt battery [not sure what they meant as my meter uses a 9V battery]. ...

2.  If not, how do I correctly test it for open or short on an HV diode?

The datasheet shows that the forward voltage could be as high as 10V - you will need a meter with at least this voltage source to be able to test these diodes. Perhaps you could find a 12V battery and use a small (<3W) lamp a a load.

https://supcache.miancp.com/data/hvgtsemi.com/upfile/pdf/2018050711530586978.pdf

[JHNC]

Fluke Instruments web page makes no mention of using an external battery or different procedure [or device] when testing an HV diode:

https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-test-diodes

There is a slight difference between using a Fluke with a diode test setting and a Fluke with no specific diode test setting but instead using the resistance [Ohms] test setting. I am assuming that this will apply to all meters in general.

I have ordered a replacement HV diode & will test it the same way I did the old one and advise on the results when completed.

[Zero999]

Fluke Instruments web page makes no mention of using an external battery or different procedure [or device] when testing an HV diode:

https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-test-diodes

There is a slight difference between using a Fluke with a diode test setting and a Fluke with no specific diode test setting but instead using the resistance [Ohms] test setting. I am assuming that this will apply to all meters in general.

I have ordered a replacement HV diode & will test it the same way I did the old one and advise on the results when completed.

That applies to single diodes. A microwave diode, is not a single diode, but a module containing many diodes in series.

[wasedadoc]

Fluke Instruments web page makes no mention of using an external battery or different procedure [or device] when testing an HV diode:

https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-test-diodes

There is a slight difference between using a Fluke with a diode test setting and a Fluke with no specific diode test setting but instead using the resistance [Ohms] test setting. I am assuming that this will apply to all meters in general.

I have ordered a replacement HV diode & will test it the same way I did the old one and advise on the results when completed.

Do NOT use an external voltage source (battery, wall wart etc) in combination with a multimeter set to resistance or diode ranges.  You risk damaging the multimeter.

[bdunham7]

Fluke Instruments web page makes no mention of using an external battery or different procedure [or device] when testing an HV diode:

That's a very basic and generic explanation of how to test 'typical' diodes which have a forward voltage of about 0.6V or so using typical multimeters which may have an open circuit test voltage of 2 volts or so.  It doesn't apply to your case.

I have a couple of similar HV diodes here that I just checked--they have a forward voltage of about 7.5V.  Most meters, even newer ones that work with white LEDs, will show that as an open circuit.  Out of all the meters I have, only three were able to test that HV diode and none of the three are very common.  Well, maybe the Simpson 270 is common enough.

I doubt your diode is bad as rectifiers have two common failure modes--shorted and disintegrated.  I'm fairly certain your new diode won't test any differently.

[Zero999]

Fluke Instruments web page makes no mention of using an external battery or different procedure [or device] when testing an HV diode:

https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-test-diodes

There is a slight difference between using a Fluke with a diode test setting and a Fluke with no specific diode test setting but instead using the resistance [Ohms] test setting. I am assuming that this will apply to all meters in general.

I have ordered a replacement HV diode & will test it the same way I did the old one and advise on the results when completed.

Do NOT use an external voltage source (battery, wall wart etc) in combination with a multimeter set to resistance or diode ranges.  You risk damaging the multimeter.

True, but a Fluke meter won't be damaged by connecting it to a battery. The correct way to test a microwave diode is with a couple of 9V batteries in series a 10k resistor.The voltage across it should be about 5 to 10V when forward biased and the full battery voltage when reversed.

[JHNC]

As I stated above, I ran the 2 tests on the new diode. The results are as follows:

The new diode tests as no component / bad using the Peak tester. The new diode tests bad using the Fluke on diode test setting. Both results are the same as with the old diode. I did get a reading of ~ 230 Meg Ohms using the Fluke's resistance setting in one direction and OL [infinite] in the other.

I then tried testing both diodes using a 9 Volt battery in series with each diode using the Fluke's 40 Volt DC setting, first in forward bias, then reversing the leads to reverse bias the diodes.

Forward biasing showed 4 VDC, reverse biasing showed 0 VDC.
I think bdunham7 explained the mystery: the standard DMM diode test function is designed to test diodes with an ~ .6 V forward voltage drop, whereas this diode has a specified maximum forward voltage drop of 10 Volts [see attachment].

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwiFguLu7eyDAxWlOkQIHW6xCZ0QFnoECBMQAQ&url=https%3A%2%2Fsupcache.miancp.com%2Fdata%2Fwww.hvgtsemi.com%2Fupfile%2Fpdf%2F2018050711530586978.pdf&usg=AOvVaw34Rod-SvIiqyMZwuBg51WX&opi=89978449

This explains why inserting a 9V battery in series with the diode and making a DC Voltage measurement accurately tested this diode. Lesson learned.

Now, the question becomes: other than HV diodes such as found in this case, what other types do we need to be aware of that will require the insertion of a voltage source - or other alternative procedure - to check accurately?

[Andy Chee]

Testing zener diodes will require an external voltage source.

[MarkT]

Does a diac count?

[BILLPOD]

EEVBLOG 121GW meter ha a 15 volt diode test setting.

[JHNC]

BILLPOD: Thanks for the heads up!

Here is a link to the EEV Blog DMM. Looks to be one fine piece of equipment.

https://eevblog.store/products/121gw-multimeter

[BlownUpCapacitor]

You can use a circuit like this:

[JHNC]

Thanks to all for the suggestions!