short-circuit rectifier EZ80 !

[jpweaner2]

Which is the symptom of a short-circuit in a rectifier tube ?

And how to make to check it .


Thank you

[kevinkr]

Read the safety and high voltage threads on this forum before doing anything.

I assume you have a dvm.

Usually if you are lucky the fuse on the primary side of the transformer will blow immediately when power is applied. That's a fairly reliable indicator, but not infallible particularly if you have a dc filament supply.

Remove the rectifier and see whether or not you have normal ac voltages at the socket with power applied. The voltages from the pins the plates are connected to should be approximately equal voltages to ground - if there is more than a few volts difference I'd be concerned that there is a short in one of the high voltage secondary windings.

You can check the tube with an ohm meter, in some cases there will be a measurable short between one of the plates and the cathode.

Verify that there are no shorts in the circuitry being powered.

Replace the tube with a new one, but use a ballast lamp (~100W) in series with the ac to test. Should there be a short this will limit current to values that should prevent further serious damage to the device. A short will result in most of the voltage dropping across the lamp and it light brightly. With normal operation it will brighten gradually to some level as the unit warms up - if normal operating currents are low it will be rather dim.

[jpweaner2]

thanks for the answer !

when I turn on the preamp , a spark come betwen the ground and the cathode and my fuse blow. I check the caps and there no short .

I check tomorrow .

thanks

[richwalters]

If heater can take extra current I always fit the EZ81. It will last longer.

richj

[jpweaner2]

HI !

I found my problem !

Last week I upgrade my caps for Jensen and i grind some track to fit in .....

I take my air compressor to clean inside my case ....... but the copper powder create the short

Thanks to all !