Triode CRTs

[jeyurkon]

Are there many vintage sets that used triode CRTs such as the 10MP4 or 12VP4 still around? Have they all been converted to used tetrode CRTs?

Just curious to know if there weren't many to begin with, or if it lead to their demise, or if I'm just not aware of them.

John

[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

[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

[cbenham]

Originally Posted by jeyurkon

Are there many vintage sets that used triode CRTs such as the 10MP4 or 12VP4 still around? Have they all been converted to used tetrode CRTs? John

The late 1940s projection sets such as the Emerson, Airline, Scott and Norelco
used the 3NP4 CRT which is a triode. I guess with 25,000 volts on the ultor it
didn't need the extra accelleration from a second grid...

[jeyurkon]

Sounds like you could do chest x-rays with it too!

Until I started reading this forum and browsing ETF I never knew that projection TV started so early. Other than mechanical tv that is.

John