Re: Tek 2465a grid bias and brightness problems

donald collie
 

Not sure if this will help or not , but I couldn`t turn down the brightness
on my 475 - turned out to be leaky dc restorer diodes, which in mine are HF
and HV diodes. Good
luck!...............................................................................................................................................................................................................................Don
C.

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On Tue, Feb 20, 2018 at 4:05 PM, David Hess <@DWH> wrote:

On Sun, 18 Feb 2018 22:02:00 +0100, you wrote:

The traces are very bright and even with the intensity control at lowest
level they are still visible, I checked grid bias adjustment but it's
already at minimum. All the intensity controls work fine but the lowest
level is too bright. I checked various test points: power supplies are fine
with minimum ripple, DAC reference voltages on A5 board are also spot on, I
checked every component in the grid bias part of the HV board and they test
good.

Readout intensity works fine.
Well, that eliminates the z-axis DC restorer as a problem which was
going to be my first suggestion.

I would start by checking that the intensity control potentiometer is
actually working. The service manual describes activating Exerciser
01 which reads back the values of the potentiometers and switches.



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