Vintage Hoffman

[Eric H]

My Avatar is a squared masked 16AP4 in an RCA, but it's nowhere near as square as that Hoffman, the sides and top on that are completely straight.

[jr_tech]

The loss of screen area is pretty dramatic when a nice straight sided 3:4 is masked off from a roundie. Double "D" shape is a good compromise.
Pix of 2 10 inch (10BP4) GE sets below:
jr

[bandersen]

Originally Posted by charokeeroad

... I would appreciate the schematic. where will I find it?

You can download them here: http://www.bobandersen.com/images/schematics/hoffman/

I couldn't scan them without breaking the binding so I took some digital pictures. I think they're quite legible, but let me know if you have any trouble reading them.

[charokeeroad]

Very readable Thanks. If the chassis isn't too crowded I may try a few cap replacements.. I see all the wave forms there are they read between the show point and chassis ground?

[bandersen]

Yes. This is a transformer set and the chassis is grounded.

[dieseljeep]

I think Hoffman made their own tuners. It was unusual to see two 6J6's.

[Tom Albrecht]

Check page 19 here for a Magnavox TV tuner with three 6J6's: http://www.earlytelevision.org/image...Sams-62-13.pdf .

I haven't seen the three 6J6 version yet, but I did work on a Magnavox recently with two 6J6's.

[charokeeroad]

Originally Posted by jr_tech

The loss of screen area is pretty dramatic when a nice straight sided 3:4 is masked off from a roundie. Double "D" shape is a good compromise.
Pix of 2 10 inch (10BP4) GE sets below:
jr

This is a really interesting comparison. Taken that both CRTs are the same size. Which one has the most square inches of screen exposed? The Double D looks biger to me but it might be that the cabinet color is lighter in color and for that reason the screen looks bigger.. and illusion.

[jr_tech]

The opening of the rectangular mask is 8-1/4 x 6-1/8 inches, the "double D" is 9-1/4 x 7 inches, so neglecting the loss of information in the corners of each display, a picture displayed on the "double D" masked CRT will be about an inch larger in each axis.
I calculate about 56.4 square inches for the "double D" and about 48 square inches for the rectangular mask (50.5 - about 2-3 sq in for the rounded corners). A "porthole" display of the same diameter (aprox. 9.25") would have a display area of 67.2 square inches. Of course, considerable information would be lost at the sides and corners.
jr