[MrFixr55]

Is the 80 ohm resistor in this set? according to the schematic, it should not be.

The design of rectifier tubes and circuits for AC-DC radios is rather interesting. The 35Z5 and later 35W4 had an interesting, tapped heater. This heater was designed to have a load of an indicator lamp in parallel with the tap on the heater, between pins 2 and 3, dropping 7.5V across this junction at the proper current. The draw of that section and the indicator in parallel with it is supposed to be 150 mA. Interestingly, in addition, usually, the input to the plate for this circuit was also on the tap. This allowed the heater and indicator to act as a fuse (albeit a rather expensive one). In case of a short or other cause of overcurrent, the heater of the 35Z5 or 35W4 and the indicator would burn out. In addition, an open indicator lamp could possibly shorten the life of the tube. A WWII hack when these tubes may not have been available to civilians due to rationing, was to bypass the "tap" section by bridging pins, thereby restoring operation, albeit at a slightly higher voltage across all heaters.

None of this exists in sets with the 35Z3, 35Z4 or solid state rectifier., including the fusing function. Therefore, I don't know how they dealt with fusing without the heater tap, resistor or actual fuse.

Post-war, Philco switched from the Loktal 35Z3 to the octal 35Z5. They then switched from the 50L5 to the Loktal 50A5. I believe that Sylvania invented the Loktal tube for Philco and possibly Motorola, as these were the 2 major innovators of Auto radios and had the most interest in Loktal tubes. In addition, Loktal tubes possibly represented increased manufacturing efficiency as having the pins integral to the tube eliminated the stap of soldering leads from the tube to the pins of a base that had to be manufactured and then glued to the tube, then the pins soldered. Loktal tubes appeared in around 1940, around the same time that the first miniature tubes for VHF and battery radios appeared. Loctal tubes were supposed to be an innovation, but it seems that for many of us, we see flaws in that innovation.

2 "mods" to consider would be to install a 0.4A fuse for shorts protection and a "globar" resistor to mitigate the "surge" in the heater string when first turned on. Tube heaters have a much lower resistance when cold than when hot. This explains why the indicator light on sets with 35Z5 / 35W4 tubes and indicators in the string will glow extremely bright, dim, then get to designed brightness, and eventually burn out. On the 122 version of this set, this is not as much of an issue, as the indicator is a 120V bulb. 3W indicator bulbs are still available and may be available at Home Depot, but definitely available on the internet. LED versions ot the "C7" nightlight / Christmas tree bulb is commonly available.