Width & Focus in DuMont RA-103

[Phil Nelson]

Here's a view of the gun. It does resemble the one shown in the other thread that you referenced, but I don't know guns from Shinola. The slanted gap shown in your photo is also present in mine, just at a different angle.

I also took three photos of the set minus the ion trap. The picture is very dim, almost invisible in normal room light. In these pics, the brightness control is turned up all the way.

In the first photo, the focus coil is perpendicular to the deflection yoke, as per the manual. Notice the dark crescent in upper right.

In the second, I canted the focus coil in the same direction as seen earlier. Not quite as cockeyed as shown there, but almost. The picture is centered in the screen and I can get sorta-good (not great) focus by turning the focus control all the way clockwise.

The third is the same as Number Two, but with contrast increased for a better picture.

The picture isn't quite as blurry as seen here. My camera has a hard time finding anything to focus on in a dark room.

I assume the picture would brighten up a lot if I put the ion trap back on. All of which is interesting, but doesn't get me any closer to solving either of these problems.

There are still some things to investigate. The resistors that Eric mentioned earlier. I can check more voltages in likely places. The manual also mentions a CRT bias adjustment which I haven't checked.

Phil