06-22-2016, 12:52 PM
Hi Terry, One would think that a city that could build rockets that send people to the moon would certainly have electrical power. A couple of years back I designed, assembled, tested at my house and helped install a 1KW solar pwr system for a friend with a cabin in the mountains, 40 miles from Huntsville. It's still working for him. I didn't ask for pay and didn't receive any. I felt he would compensate me in some way to some extent. (Oh well) I worked with solar power systems for orbital payloads for NASA here in Huntsville.
A friend inherited the Philco 38. He's an electrical engineer but with essentially no vintage tube radio experience. He realized that it was a battery set and asked if it was worth building a battery eliminator. I suggested that if all the tubes were good, then it would not be much effort to build a battery eliminator. In the late 40s and early 50s I would occasionally see an old battery radio. I remember the large plate (90V) and filament (1.5V) battery. I saw many with all tube filaments blown where the 90V had been shorted to the filament supply wire. This radio requires 135, 67.5, 7, 3, and 2 volts.
This story is getting long so I'll just say I got hooked with the whole job; building the pwr supply and making the radio play. It's like the mountain solar power system all over again!
Now to the problem at hand. Per Arran's comment, aligning the marker at the low end of the dial scale with the pointer light and the tuning capacitor fully meshed appears to be be the proper method for placing the dial scale assembly on the capacitor shaft. The oscillator can be made to track. Thanks Arran.
With the oscillator tracking, the radio still had very poor sensitivity. Better reception was had from a signal placed on the control grid of the oscillator-mixer than on the antenna terminal. I checked the antenna coil and found an open primary. As a result of corrosion, it was open in 2-3 places. I had no 38G wire so I rewound 12-13 turns with the smallest wire size I have; #32. I placed the antenna terminal side of the primary winding next to the low side of the secondary. I am getting coupling but the signal from the antenna terminal is still not as strong as when coupled directly into the top grid of the mixer-oscillator tube.
I have gone through the recommended alignment process.
I have #38 wire coming. I need suggestions and comments on how many turns, placement, hints etc.
Gene, K4ZQM
A friend inherited the Philco 38. He's an electrical engineer but with essentially no vintage tube radio experience. He realized that it was a battery set and asked if it was worth building a battery eliminator. I suggested that if all the tubes were good, then it would not be much effort to build a battery eliminator. In the late 40s and early 50s I would occasionally see an old battery radio. I remember the large plate (90V) and filament (1.5V) battery. I saw many with all tube filaments blown where the 90V had been shorted to the filament supply wire. This radio requires 135, 67.5, 7, 3, and 2 volts.
This story is getting long so I'll just say I got hooked with the whole job; building the pwr supply and making the radio play. It's like the mountain solar power system all over again!
Now to the problem at hand. Per Arran's comment, aligning the marker at the low end of the dial scale with the pointer light and the tuning capacitor fully meshed appears to be be the proper method for placing the dial scale assembly on the capacitor shaft. The oscillator can be made to track. Thanks Arran.
With the oscillator tracking, the radio still had very poor sensitivity. Better reception was had from a signal placed on the control grid of the oscillator-mixer than on the antenna terminal. I checked the antenna coil and found an open primary. As a result of corrosion, it was open in 2-3 places. I had no 38G wire so I rewound 12-13 turns with the smallest wire size I have; #32. I placed the antenna terminal side of the primary winding next to the low side of the secondary. I am getting coupling but the signal from the antenna terminal is still not as strong as when coupled directly into the top grid of the mixer-oscillator tube.
I have gone through the recommended alignment process.
I have #38 wire coming. I need suggestions and comments on how many turns, placement, hints etc.
Gene, K4ZQM
