Re: 7904 - Very Dim Trace


I did not have to adjust the grid bias to get a usable display.

I would check that resistor which is in series with the heater. It is
possible to check the voltage at the heater using a floating RMS AC
voltmeter. The frequency is about 50 kHz.

On 14 Feb 2016 15:12:24 -0800, you wrote:

Thanks for your report David. I appreciate your taking the time to run the experiment. Yes - I too found there's a right and wrong way to pull the PDA connector apart...

On my scope, after the dimming event occurred, at first I saw no trace at all. It was only after I tweaked the grid bias that I was able to see a dim trace. Maybe it was mis-adjusted in the first place, but I have lingering doubt, that dropping from 21 down to 14 kV would cause the dramatic dimming I am seeing. I'll re-check the deflection sensitivity, but as I recall. it was spot-on.

Comment about carbon resistor in the heater circuit noted - thanks.

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