Re: 5116+5D10 intensity problem


Chuck Harris
 

When the Anode voltage on the CRT is lower than it is supposed to
be, the electrons in the beam travel proportionately slower than
they should. Because they are slower, they spend a longer amount
of time to passing between the deflection plates. This means
longer time means that the force the electric field between the
plates applies to the electrons, has a longer time to work at
deflecting the electron beam. Which further means the electron
beam will be deflected more than it would at the proper voltage.

What you should take away from this is: If the anode voltage is
low, everything on the CRT screen will be expanded (magnified) out
much larger than it should be.

That your readout is expanded outside of the screen is nearly
perfect proof that your anode voltage is low. You can guestimate
how low by how much the expansion is. But it is most definitely
lower than it should be.

-Chuck Harris

Yeun-Jung Wu wrote:

Hello Harvey:

Thank you for your hint on future diagnosis. I will start collecting more information on epoxy coated transformer first.

5D10 seemed to work fine except read out information had been expanded outside the screen. Now I understand why red LED "possible under-sampling" would lit: I was using slow time base to watch two nearly identical 7kHz since wave superimposed together to form a nice envelope. There were lot of wave form variation during long accuqsition time but the available memory space for storing waveform was limited. When I select faster time base such that several cycles was within the range of one horizontal division that warning went away.

More than 5 year's ago I bought a Tek high voltage probe from eBay. There was an empty can supposed to contain liquid with high dielectric strength, something similar to banned CFC freon. For 4.5kV maybe I can fill some other liquid and give it a try.

Best Regards,

Yeun-Jung Wu

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