Jim McDowell
1. You need a 50B5 and need it now!. All you have to do is reverse pins 1 and 2 and reverse pins 5 and 7, and now your set will use a common 50C5 tube.
2. If you need a 25A6 you can just plug in a 25L6.
3. No matter how well a radio seems to play always replace the coupling capacitor between the first and second audio on pin 5 of octal tube types and pin 4 of 41, 42, 43, type tubes. This capacitor most often leaks and will distort the sound after the radio gets warm. Also replace the tone capacitor on pin 3 of octals or pin 2 of 41 type tubes. You may also remove this capacitor if you want more treble.
4. To protect a power transformer in a set, install a one-half amp fuse between the high voltage secondary center tap and ground. In some sets the secondary does not go straight to ground. In this case, place the fuse between the secondary center tap and the rest of the circuit. It is also a good idea to check all dial light wires.
5. In late twenties and early thirties transformer coupled push-pull type sets (some dog coffins) the tone can be greatly improved by placing a .01 capacitor in series with a 10K pot and connecting the leads to the control grids (first grids of output tubes) and then adjusting it to your taste. This adjustment works in the mid frequency range and will enhance the lows and highs if adjusted properly.
6. Tone controls may be added to any radio! To do so add a .005 mfd. @ 600 volt capacitor from the plate of the first audio amplifier through a 20K pot to ground.
7. Switches that you can't seem to get clean will clean up using Blue Stuff. a TV tuner cleaner sold only at electronics parts houses (in San Francisco. ARDCO, 1583 Howard St., They also supply a lot of other things that we need to repair old sets). This will also work on controls as well. Radio Shack has lots of stuff like this, and a selection of high voltage capacitors, and 1/4 watt resistors as well.
8. Weak reception on a superheterodyne set may be caused by open bypass capacitors in the I.F. stages.
9. Those valuable little metal sets can be made safe to operate by using a grounded three wire cord and plug. Just replace the old cord with the new one and ground the third center wire to the cabinet. Make sure the cabinet is grounded by connecting an ohm-meter to the cabinet and the third (big) prong. Use these sets only on a grounded outlet.
10. Old FM band 43-48 mHz sets can be useful still to pickup TV sound. Connect the antenna of the radio to a metal plate under the TV set and tune the radio until you hear the TV sound. The sound will change as you change channels on the TV. Some TV's are so well shielded that you may have to open up the TV and glue a small piece of metal on top of the video I.F. chip and run a wire to the FM antenna terminal, Do not make any direct electrical connections to the TV!!
Have Fun!
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