Re: Testing tetrode tube

by **admin** Tue Sep 28, 2021 1:03 pm

Hi Gertie,
I think you will find that the object is to see if the tube can still carry current that the cathode has not been stripped (causing low emission).

As Ivan wrote, you should check the continuity to be sure that no electrodes are shorted. Other than this the major faults with power tubes is low emission, which is what this test checks.

BR Harry

by Gertje Tue Sep 28, 2021 6:51 am

Thats my question : what/how does the current flow into a tetrode if you test a tube at that way.
If you know that for example a 4CX1500B has about 1 watt of dissipation on the control grid.

by **Ivan** Mon Sep 27, 2021 7:17 pm

Hi,
it probably is O.K. I saw a pentode (RV12P2000) with grids connected to the anode used as a rectifier diode in a schematic from the 50s. The tube should be tested for shorts first. The currents seem to distribute properly if there are no shorts nor disconnections inside.

VBR from Ivan

by **Ruud** Mon Sep 27, 2021 10:24 am

Doesn't feel right to me, because you have no idea how the currents (grids and plate) are divided.

by Gertje Mon Sep 27, 2021 10:14 am

https://www.youtube.com/watch?v=aHoiPuESpe4

I found this video how someone test a tetrode 4CX1500B tube.
Can it be done like that ?
Grid + screen + anode togheter and heating up.
What about the current in the grid and screen ?

Thanks

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Testing tetrode tube