Line-cord antenna coupler - safe on new cord?; tube substitutions

[Jeffhs]

Originally Posted by Chad Hauris

50EH5 is a higher gain tube than 50C5...it was often used in record players with only a single tube amplifier. I would just keep using the original tubes until such time as the reception appears weak...radios are pretty forgiving of weak tubes unlike how TV's can be.

I've never actually seen a phonograph with a one-tube amplifier, but I have heard of them. Never saw one with a single 50EH5, though. The one-tube phonos I've heard about have had a 117Z3 tube, wired in series with a 90-volt turntable motor. As I understand it, if the tube filament burns out in one of these, the motor will stop as well.

I would think there would have had to be at least two tubes in any phonograph that used a single 50EH5 as an amplifier stage, the second tube being a 35Z5, 35W4 or similar type rectifier (with a dropping resistor to take up the remaining 32 volts) unless, of course, a selenium power rectifier was used. Also, one other problem with one-tube phonos that used the 117Z3 could arise if the tube developed a heater-cathode short. Since the tube filament is connected directly across the AC line, such a short would blow a fuse or kick out the circuit breaker immediately upon turning the set on or even plugging it in (the switch need not be on), and could burn out the phonograph motor at the same time by virtue of putting the full line voltage across the 90-volt winding unless the circuit was fused. I doubt very seriously, however, if any of the one-tube phonos using line-operated tubes had line fuses, although goodness knows it would have been a good idea from a safety standpoint.

As to your suggestion on leaving the original tubes in my MJ1035 as long as the radio works well, that is exactly what I intend to do (as I mentioned in a reply to Tom Bavis's post on that subject). The radio seems to work well, except for an intermittent volume control, so I will leave everything alone until or unless a tube goes or the radio develops some other problem. The adage "If it isn't broken, don't fix it" certainly applies here. Well-meaning attempts at "repairing" something that is basically working have ways of going terribly awry, often leaving the device with more problems than it had before the "repairs" were begun.