Vintage Hoffman
 

I would appreciate any feedback on this Early 50s Hoffman. The channel selector is of particular interest it has many of the channels showing the station id. like KRON channel 4 and KTLA channel 5. Is the tube a 12UP4? How about the year, 1951-1952? I there a chassis number?

Thanks

I suspect the CRT is an early rectangular model, maybe a 14 or 16"? Possibly/probably metal? it looks like it has an insulator around the front.

The 12UP4 is a round 12" metal tube, used in Zenith Portholes only afaik.

My Hoffmans have the channel tabs with the stations also, mine are from Los Angeles.

I don't know what the chassis is like on this one, probably similar.
They are really nice sets in my opinion.

The early rectangular CRTs (14", 16" and 20" ) were not made in metal... but indeed, it appears that perhaps this set has an insulator around the CRT opening in the bezel. :scratch2: Perhaps a 16" metal round tube lurks behind the bezel? Nice set!
jr

That's what I think too. it a big roundie behind the bezel... (that woud be nice) but an early rectangular would be a treat too especially if it's strong.

:D

This is exciting. When I go to pick up this set I will be anxiously awaiting the first sight of the CRT. Is it round is it rectangular? What is the number on the CRT? Is it Good? how strong is it? How do I get it into my car and drive away without giving away my excitement to this generous giver.. After I'm away for a few blocks I'll stop and just look at it and realize it's mine.

"The cabinet measures 37.5 inches high from the floor, it is 22 inches deep and 26 inches wide. I couldn't find a year on the back, but the model number is 877 and chassis number is 171. There is also an interesting 4 prong plug in the back that says "UHF adapter for future channels"

Notes from the giver..

I found it in Riders Vol 6 and Beitman's from 1951.

They show the UHF converter plug carries Ground, 6.3 VAC (filament supply) and +265 Volts.

Thanks for looking. Tom Albrecht found it in Sams and although Sams shows that model number with a 19AP4 it also mentions that there are some variations on that model. It doesn't look like a 19" but I guess it could be based on cabinet size.

Beitman's lists the 171, 171, 173 and 175 chassis together because they are so similar. Here are the CRTs they use.

170 - 14CP4
171 - 16TP4
173 - 17BP4
175 - 19AP4

I see I have my homework cut out for me. Are all these tubes roundies?

The 19AP4 is a metal roundie. The rest are glass rectangular.
jr

I'm almost certain it's not a round tube, they wouldn't have masked it off like that if it was, it'd probably have a double D screen if that was the case.

If Beitman's is correct, then you've got the 16" glass rectangular 16TP4. I can scan the schematic if you'd like.

I'm inclined to think it's a 16TP4,all glass, based on the look and the model # 171.

http://www.shinjo.info/frank/sheets/093/1/16TP4.pdf

I'm hoping the CRT comes out with the chassis and that the CRT isn't bolted to the cabinet.

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

Most likely... the service literature (Beltmans) indicates that it is a 16TP4, but I wonder why the cabinet is so deep? :scratch2:

Several Admiral models from 1949 did use a rectangular mask in front of a metal 16" roundie.
http://www.tvhistory.tv/1949_Admiral_AD3.jpg

I have an Admiral branded 16AP4 that was from a similar model.

jr

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.

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

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.

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?

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

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

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.

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.

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