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Update on this set:
Have been brushing myself up on TV theory, and discovered some peculiarities about this TV. For one thing, it has RGB screen controls, but not drive controls. It seems to me that this is a design compromise, which makes it difficult to compensate for uneven aging of the CRT cathodes. Specifically, when the screen controls are set for proper white balance, the tint control has to be adjusted fairly far off centre towards red, in order to get accurate skin tones. Is this really a compromised design, or is there another way to go about setup?
Remembered I had another tube tester packed away. It is an EICO model 667, and once I found a comprehensive setting chart online, I was able to test all of the tubes in the TV.
Weak tubes include the final video amplifier, and also the 10Z10, as well as the colour burst oscillator. The only tube which tests in the "red" zone of the tube tester is the aforementioned colour burst oscillator. Luckily the horizontal output tests well into the green zone, at 120%
Out of curiosity I tested the old tuner tubes, 2HA5 and 4GJ7, and both tested in the "yellow" zone of the tube tester. In the set however, they completely ruin performance, the picture becomes overwhelmed with noise and snow. It makes me wonder what effect new tubes will have in other positions which are currently reading weak good, or marginal.
The set is displaying a few symptoms which seem to indicate a weak CRT, according to what I have read. Will reserve judgment until all small tubes are good, but symptoms are as follows:
1. Green appears a bit weaker than other colours, grass is always a bit browner than on other TVs. Nothing awful, but all the same apparent
2. When contrast control is anything above mid level, text on the screen has a bit of a shadow, “blooming” type appearance. It is still legible, but there is a definite loss of sharpness. This effect is worst with text on a dark background, such as movie credits or TV guide, and does not seem to affect normal video.
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