Triode CRTs

[jeyurkon]

Originally Posted by Don Lindsly

There are a few more; electrostatic tubes like the 7JP4, 8BP4, 10HP4, etc.

The Philco 1207/1208 uses a 12WP4 thin neck triode. Converting the Philco is a little tricky so more have been scrapped than converted to conventional 12 inch.

TVs using triode CRTs were soon phased out in favor of the brighter and crisper pictures produced on tubes with a screen element. Power supply advancements also helped, providing more sources for screen voltage. TVs using RF power supplies or low B+ voltages didn't have a convenient 350 volt source.

Don

Thanks, that's interesting. In a day or two I should have the Sylvania that uses a 10MP4. Hopefully I won't have to replace it with a 10BP4. But if I do it'll be interesting to see how I like the picture.

I grew up with my eyes glued to a 12VP4. I've never cared much for modern B/W CRTs. Probably like people who prefer margarine over butter because that's what they're used to.

One difference I'm sure of that bothers me is with modern CRTs you see color splotches. It's like they mix three different phosphors to get white. It's a truer white, but not my preference.

The other issue is the triode characteristic where it compresses the bright levels. I'm wondering if that was something else I got used to.

Brighter and crisper might not be right for me.

John