Width & Focus in DuMont RA-103

[jeyurkon]

Originally Posted by jr_tech

But the gun does not appear to be a 12JP4...remember a 12JP4 does NOT require an ion trap, your gun appears to be a tilted offset/ slashed field type which requires a single ring magnet. Why would the factory put the wrong gun in a tube? I suspect that rebuilders often made substitutions when the proper gun was unavailable.

The re-neck seal could possibly be hiding under the yoke or focus coil.

Also, the first letter of the logo on the label does not look like an "H", but instead has a closed top... so I don't think it is "HyTron" but perhaps something designed to look similar.

jr

Any idea of which type it could be? I think this is a diagram of the tilted offset/slashed field that you're describing. It's from the 1969 RCA tube design book.

John