Fernseher und Farbfernseher aus der Anfangzeit des Fernsehens und des Farbfernsehens - Homepage Eckhard Etzold
The Raytheon M-1101 is an American TV set manufactured in Raytheonís Belmont Radio plant in Chicago on October 1949, the peculiarity of this set is the image, which has a round shape, employing the whole screen area (unlike most of the other sets, where the CRT face was more or less masked to give a rectangular appearance), this style of TV is known as "porthole", like the "windows" on a ship. The CRT (type 12LP4) is a 12" diameter and having a relatively low deflection angle, about 60į, itís very long, so the cabinet has to be quite deep, in order to contain it.
Made in Raytheonís Belmont Radio plant in Chicago (Illinois) the tv set was probably originally sold in 1949 in Detroit (Michigan) due to a worn label still visible on the masonite back cover, and then transferred some way from USA to Canada, during the past 60 years, ending in Bridgewater (Nova Scotia), and then finally shipped by Air-Canada Cargo and Lufthansa Cargo to Italy packed into a robust wood crate, thanks to the great efforts of Angeloís cousins John and Shelly from Nova Scotia.
Beside the great work Giulio has done on the main core of this TV set other works were carried on the rest of the set by Angelo, here follows a brief description. The set was completely dismantled leaving a naked chassis and an empty wood cabinet; the cabinet had some major chips and scratches. The chassis was carefully cleaned with mild soap, with a spray ammonia based glass cleaner and, in some particularly dirty area, using gasoline; the chassis was originally protected by a pale green primer coat that, with time passing, suffered in some areas some light oxidation from the lower metal. So far after deep cleaning it was decided not to proceed to repaint it and the whole chassis was left "as is" in still exceptional good condition.
From the first photos, it is evident that this chassis has never been fixed in itís life, all the components are still the original ones, except a handful of tubes, a normal thing. During the restoration, Giulio tried to maintain as much as possible the originality of the chassis, hiding the new capacitors inside the shell of the old ones, this is quite simple to do, except for the moulded ones, in this case you have to carefully cut and split them open, extract the old guts and, once the new one is in, reseal the shell. Same thing is of course possible with the electrolytics, here the space is usually not a problem, as the old ones are usually quite a bit larger than the new ones, in the same fashion the "canned" filter capacitors located just under the CRT neck were restuffed. For the resistors, the hiding work is not so simple, so the changed ones had to be left "as is", unless some so called NOS resistors were available.
The missing EHT cage was reconstructed with exact dimensions taken from the pictures showed on the original available PHOTOFACTS schematics of this model, the cage is made with thin zinc plated steel foil that was bent and tin welded to fit into the still existing bottom receptacle.
The horizontal output section uses a 6BQ6GT (output tube) and a 6W4GT (damper tube), in conjunction with a 1X2B (EHT rectifier) to produce the 11kV needed for the final anode of the 12LP4. The flyback transformer is not the common autotransformer with various taps to connect the damper diode cathode and the horizontal deflection coils, but it is a true transformer with a separate primary and secondary windings. This arrangement was used only on early TV sets and is not very common in Europe (at least, the author remembers only 1 TV set with this arrangement). The EHT cage, needed to limit the RF irradiation produced in the horizontal output section, was missing, so Angelo did rebuilt it.
Another particular thing is the CRT requires a double ion trap, one part (the one nearer the tube socket) has a stronger magnetic field, the other part has a weaker field and its purpose is to pull back in the right direction the electrons affected by the stronger part of the ion trap.
The rejuvenated Raytheon is now used and enjoyed at Angeloís home; the 625 lines video signalís coming from an external satellite tuner then converted into Channel 3 or 4 and sent to the tv set by a flat wire thru a balun impedance matching transformer (300/75 ohms).
02/04/2008, Giulio Maiocco and Angelo Rostagnotto
6AG5, 6J6, 5x 6AU6, 6T8, 6K6GT, 6SL7GT, 6SN7GT, 6BX7GT (originally 1x6SN7GT), 2x 6AL5, 6BQ6GT, 6W4GT, 1X2B, 12AU7, 5U4G, 12LP4. All tubes used on the set are new SYLVANIA made valves, most of them were found NOS-NIB originally made in late 40ís and early 50ís.
Photos: © Angelo Rostagnotto, 2007.
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