Why do 1N4007 diodes fail at 900V but test good with an ohmmeter?

[Ravaner]

Hello. I use 1N4007 diodes in a voltage multiplier near the maximum authorized 900 V (max reverse 1000 V). Some don't work and I replace them, but ... With an ohmeter they look correct and more using them with medium voltage ( 200 V ) they work perfectly. So they aren't destroyed, could someone explain me this phenomenon ?

 

[fleem]

All diodes are "Zener" diodes. They leak a little when the reverse voltage gets high enough. They won't be damaged as long as they don't get too hot. Also, the reverse voltage at which they leak depends on temperature, and certainly there'll be variation from one 1N4007 to another.

 

[Ravaner]

Thanks for your answer