WinDAS White Point Balance guide for Sony Trinitron CRTs

[spacediver]

This may be of value to some!

http://hardforum.com/showthread.php?t=1830788

[old_tv_nut]

Useful procedure. A minor mistake in the background info - D65 is the color of light from an overcast sky, not direct sunlight.

[spacediver]

thanks for that, it appears you're correct, although it's hard to track down the original reference:

CIE (1967) Recommendations on standard illuminants for colorimetry, in: Proceedings of the CIE Washington Session, Vol. A, CIE Publ. 14, pp. 95–97.

I'll make the correction when I make my next update!

[spacediver]

btw I have some questions that I'm trying to figure out, and perhaps you could help.

Here's one of them:

According to Randy Fromm, and Kenneth Compton, the barium coating on modern cathodes provides a source of electrons, and this source is finite, and is the ultimate determinant of cathode lifespan.

However, according to some folks on DutchForce, this model of how things work is completely inaccurate: what is really happening is that the electrons are provided by the power source, and there is therefore an essentially infinite supply.

Do you have any thoughts on this matter?

[old_tv_nut]

Originally Posted by spacediver

btw I have some questions that I'm trying to figure out, and perhaps you could help.

Here's one of them:

According to Randy Fromm, and Kenneth Compton, the barium coating on modern cathodes provides a source of electrons, and this source is finite, and is the ultimate determinant of cathode lifespan.

However, according to some folks on DutchForce, this model of how things work is completely inaccurate: what is really happening is that the electrons are provided by the power source, and there is therefore an essentially infinite supply.

Do you have any thoughts on this matter?

Of course, the power supply can supply all the electrons that the cathode will emit, but how many it emits is determined by the cathode chemistry and temperature. If this were not true, cathodes would never wear out. But, they do wear out.

If you look at the failure statistics of most electronic parts, you see a "bathtub" curve: a high rate of failure early ("infant mortality," which can be weeded out by a break-in period) followed by a hopefully long period of low failure rate, and then a gradually rising rate again for wear-out due to various degradations over time.

Cathodes, however, are in wear-out mode immediately when they first go into use, with a constantly rising failure rate. If the maker can maintain the correct recipe for making tubes, the rise in failure rate will be gradual enough for practical application; if not, you get some of the infamous examples of lousy short-lived tubes.

The only tube parts that are more sensitive to process variations are the photoemissive and photoconductive surfaces that were used in camera tubes.

[spacediver]

Originally Posted by old_tv_nut

Of course, the power supply can supply all the electrons that the cathode will emit, but how many it emits is determined by the cathode chemistry and temperature. If this were not true, cathodes would never wear out. But, they do wear out.

This is the crux of the disagreement:

According to Compton (page 29):

From the very start of its emissive life, the cathode is depleting the available electrons. The drive of the video amplifier does not contribute to the electron flow; it is merely a voltage potential that causes electrons to flow at a specific rate. Barium is the source of electrons in both oxide and dispenser cathodes. The process of giving up electrons leaves behind atoms that are now short of valence electrons. This in turn causes cathode material to migrate to the G1 area and deposit itself."