Quote:
Originally Posted by timmy
Is there any such thing as keeping color level or even brightness level down to prolong the life of a 21fb or fj crt. Or even lower heater voltage.
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A CRT (or any tube) is in wear-out mode from the first time it's turned on. Reducing beam current definitely extends the life of a CRT, but in an odd way compared to amplifier and diode tubes.
CRTs draw current from a variable area of the cathode depending on the amount of beam current. That's why the spot size is bigger in the highlights, and why the beam current vs. g1-cathode voltage follows a power law (gamma) about 2.5 rather than the theoretical value of 1.5 for an amplifier tube with more uniform current over the whole cathode. So, even though you extend the life of the CRT by running lower beam current, eventually the cathode center area will wear, you will have to turn up the drive to get the same brightness, and current will be drawn from a larger area, increasing spot diameter ("blooming") as the tube wears out.
So, if you can live with a dimmer picture, you will get longer life and smaller spot size (better focus).