Results of my Sencore CR70 Field test, and some questions

[Electronic M]

Some inline gun tubes (trinitrons are inline) have a single grid or a single cathode.

There is a difference between video (AC) drive and DC bias. You can drive a tube with AC video signal at grid and/or cathode (the CRT don't care) and things will work fine. DC bias (which is the test condition on a CRT tester) is what your CRT elements will be at if your video stage is not operating (and what the DC voltages on the tube will hover near when driven with video). DC bias is the relative DC voltage of the cathode and grid....assuming plate (which may be the focus electrode or similar when on the tester) much more positive than cathode.

[spacediver]

Originally Posted by Electronic M

Some inline gun tubes (trinitrons are inline) have a single grid or a single cathode.

There is a difference between video (AC) drive and DC bias. You can drive a tube with AC video signal at grid and/or cathode (the CRT don't care) and things will work fine. DC bias (which is the test condition on a CRT tester) is what your CRT elements will be at if your video stage is not operating (and what the DC voltages on the tube will hover near when driven with video). DC bias is the relative DC voltage of the cathode and grid....assuming plate (which may be the focus electrode or similar when on the tester) much more positive than cathode.

Ah! So if I'm understanding correctly, during the emission testing, when the bias is set to 0, it doesn't matter if this is achieved by increasing the grid voltage until the potential between control grid and cathode is 0, or whether cathode voltage is decreased until the potential between control grid and cathode is 0. They both achieve the same condition. And this condition is what would occur when driving a gun to peak luminance.

I assume that when the bias between grid and cathode is 0, g2 is what is pulling the electrons, and creating beam current. How does the CRT tester know what voltage to apply to g2 though?