Electronics > Projects, Designs, and Technical Stuff
Testing 1N4007 with a megger
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mzzj:
Failed components like these are always real pleasure to try to find. Oldschool CRT monitors often had components that would measure ok with DMM but leak too much in real circuit.
T3sl4co1l:
Hm, wonder if the avalanche withstanding capability varies with manufacturer.

I would expect a good diode to just simmer in avalanche at say 1200V or thereabouts.  Rather nasty, the results seen here!

Tim
mzzj:

--- Quote from: T3sl4co1l on November 01, 2019, 08:27:34 am ---Hm, wonder if the avalanche withstanding capability varies with manufacturer.

I would expect a good diode to just simmer in avalanche at say 1200V or thereabouts.  Rather nasty, the results seen here!

Tim

--- End quote ---
Or you could interpret the results that leakage current increases  at 1350v and diode enters avalanche knee at around 1.8kV

It is indeed "simmering" with the 3mA current limit on the megger and 1.8kV applied = 5.4W !

If OP still has time to play with the megger it would be interesting to know what happens if you test couple of diodes with the current limited to 0.5mA or so. (less than 1 Watt power at avalanche)
MagicSmoker:

--- Quote from: mzzj on November 01, 2019, 10:25:29 am ---...
It is indeed "simmering" with the 3mA current limit on the megger and 1.8kV applied = 5.4W !
...

--- End quote ---

Bingo! That's why you need to really limit the current (or the time spent) in avalanche for a runty little 1A diode which has a nominal Pd rating of maybe 1W... (and that's if you keep the legs extra long and don't place it next to anything else that gets hot).

taydin:
Ok, attached are the results with 10MOhm in series of the diode, ramping to 2.5 kV, reverse polarized. The Y axis is again microamps.

I have also added the pdf output that has each individual voltage measurement.
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