A Zenith Chassis ... Model 79 - Videokarma.org TV - Video

solidjackson · #1 03-16-2009, 07:34 PM

Last week I found this old Zenith AM/shortwave T.R.F. receiver while looking at some other old stuff. Must have weighed about 50 pounds! It appears to go back to the early thirties.

Yeah, the speaker has seen better days. This unit has a separate power supply with huge transfomers.

What seemed interesting to me is that there wasn't a glass dial on this particular model. Just a big dial gear with numbers. At least there aren't any strings to break. It's got a huge tuning capacitor.

I was able to find the schematic on a CD that has the first "Riders" book on it. Unfortunately, I don't have all the tubes for it, but it uses two 45s, three 24-As, and 3 other tubes I can't remember the number of. It's got a phono input, too.

I've never worked on anything quite this old. Are these sets anything to write home about? I figure it oughta make an interesting project if I can find something to stick it in!

Tony V · #2 03-16-2009, 07:58 PM

If it has two 45's then it should have push pull output and should sound nice once restored. You dont see many of these early Zeniths come up that often. Looking at the design, it should have been made in the 1929 to 1933 time frame. Since it has a phono input, it was definately a console unit.

Reece · #3 03-17-2009, 11:49 AM

Doubt that a TRF of that era had shortwave. The markings on the dial aren't clear in the photos but one side is probably frequency and the other may be either the meters equivalent of the frequency, or a 0-100 logging scale.

The speaker would be a candidate for reconing.

Reece

solidjackson · #4 03-17-2009, 09:38 PM

Yeah, you're right. One side of the dial has the scale 200 t 550, and the other side goes from 550 to 1550. I checked the schematic, the three other tubes are type 27. Thanks for the replies!

Reece · #5 03-18-2009, 11:18 AM

So the other scale is meters: 550 kc. = 545 meters; 1500 kc. = 200 meters. In the early '20's they went by meters rather than kilocycles, and blended over to kilocycles in the thirties but kept both scales for a while.

Reece

solidjackson · #6 03-19-2009, 02:38 PM

BTW, here's a pic of the underside. I don't think I've ever seen anything like those big silver cans before.

gadget73 · #7 03-19-2009, 08:55 PM

Those big cans are often seen in neutrodyne sets. A neutrodyne is basically a shielded TRF with some feedback circuits to null out the oscillation problems that early TRF stuff had. My Fada neutrodyne is all 27's with I think a single 45 for output. It also has big cans like that, totally different chassis layout though.