Re: 454 screen brightness issues?

Albert Otten

Hi Jack,

I had my leads wrong, the grid is actually around
150 volts ABOVE the cathode, which explains everything. Thank God it isn't
a broken grid, but... the Z axis board is certainly messed up if something
like this is going on.
Now that you confirm that you made a sign mistake (question in my previous response) the fault is certainly not in the Z-axis board, diagram <16>, or in the CRT itself. In y opinion it must be a fault in the CRT supply circuitry diagram <17>. Probably in the grid supply. Probably an open "bottom" end of the grid bias pot R1447. Did you measure the resistance between wiper and joint of R1447/D1440? Does it go to zero in one detend of the wiper?


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