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.

[radiotvnut]

Originally Posted by Jeffhs

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.

I know this is OT; but, I'll share my two cents on phonographs since you brought it up.

I've seen plenty of those record players from the '50's and '60's. Most of the mono units used a 25L6 tube in series with a 90 volt phono motor. The rectifier was usually selenium. Some of the later ones had a silicon rectifier. I've seen some stereo models that used two 60FX5 tubes in series. The main thing I dislike about these one tube record player's is that they require a high output cartridge (2 to 3 volts) to drive the tube. The better models used a lower output cartridge and had a preamp tube ahead of the output. The only portable record players I've seen with fuse protection were the classroom models (Califone, Newcomb, Audiotronics) and the "talking book" record players for the blind furnished by the library of congress. Some of those had a circuit breaker instead of a fuse.

[Old1625]

Originally Posted by radiotvnut

I know this is OT; but, I'll share my two cents on phonographs since you brought it up.

I've seen plenty of those record players from the '50's and '60's. Most of the mono units used a 25L6 tube in series with a 90 volt phono motor. The rectifier was usually selenium. Some of the later ones had a silicon rectifier. I've seen some stereo models that used two 60FX5 tubes in series. The main thing I dislike about these one tube record player's is that they require a high output cartridge (2 to 3 volts) to drive the tube. The better models used a lower output cartridge and had a preamp tube ahead of the output. The only portable record players I've seen with fuse protection were the classroom models (Califone, Newcomb, Audiotronics) and the "talking book" record players for the blind furnished by the library of congress. Some of those had a circuit breaker instead of a fuse.

Some of those old portable phonographs were notoriously dangerous. What's worse is that they were more commonly used in the kiddie playroom or bedroom than as a livingroom entertainment. Left unsupervised by adults they became a serious fire and shock hazard.

Most of the Califones and Newcombs I encountered had a transformer power supply, but they may have made them both ways.

[Jeffhs]

Originally Posted by Old1625

Some of those old portable phonographs were notoriously dangerous. What's worse is that they were more commonly used in the kiddie playroom or bedroom than as a livingroom entertainment. Left unsupervised by adults they became a serious fire and shock hazard.

Most of the Califones and Newcombs I encountered had a transformer power supply, but they may have made them both ways.

I had a Califone phonograph years ago that came from a school which was upgrading equipment in its A/V department. The phonograph was transformer-powered, IIRC, and had about the most powerful amplifier I ever heard of. I never turned it up full blast, but thinking back on it, I bet it could blow the roof off a building if run wide open. Then again, Califones (and probably Newcomb phonos as well) were built this way so that they could be heard in the back of a large classroom, if necessary.

I did not stop to think that the old one-tube phonographs were or could be fire or shock hazards under the right (or wrong[!]) conditions, but it's true, especially since these were transformerless chassis that were connected directly to one side of the line. I knew someone years ago who had a transformerless phonograph (whether it had a one-tube amplifier or not I couldn't tell you) that was severely damaged when water was spilled into it. I was told there was quite a bit of smoke coming from it right after the mishap, but fortunately there was no fire. Unfortunately, however, the phonograph was destroyed because of the damage to the amplifier. These small phonos may not have been worth repairing, even in the '40s-'50s, due to the sheer simplicity of the amplifier circuitry; I don't think there was much to these except the tube, a filament dropping resistor (if an amplifier tube other than a 117Z3 were used), a selenium rectifier, the loudspeaker of course, and the volume control with an AC switch on the back.

BTW, speaking of the 117Z3 tube, how many one-tube phonographs used this tube as an amplifier, with a selenium rectifier? I asked this question earlier in the thread, but it was never answered. I would think that phonographs using the 117Z3 would have almost ridiculously simple amplifier circuitry consisting of little more than the tube, volume control and a speaker. Talk about an electronic circuit in which almost nothing can go wrong! The only thing that could really go wrong with these, I think, is that the tube would eventually burn out or short.

Were the phonos with the 117Z3 among those that required a high-output cartridge to get any kind of volume? If a cartridge with an output on the order of 2 to three volts was needed to drive the tube to usable volume level, the 117Z3 (and probably most other tubes used in one-tube phonograph amplifiers) must not have been a very powerful amplifier to begin with.

[radiotvnut]

Originally Posted by Jeffhs

I had a Califone phonograph years ago that came from a school which was upgrading equipment in its A/V department. The phonograph was transformer-powered, IIRC, and had about the most powerful amplifier I ever heard of. I never turned it up full blast, but thinking back on it, I bet it could blow the roof off a building if run wide open. Then again, Califones (and probably Newcomb phonos as well) were built this way so that they could be heard in the back of a large classroom, if necessary.

I did not stop to think that the old one-tube phonographs were or could be fire or shock hazards under the right (or wrong[!]) conditions, but it's true, especially since these were transformerless chassis that were connected directly to one side of the line. I knew someone years ago who had a transformerless phonograph (whether it had a one-tube amplifier or not I couldn't tell you) that was severely damaged when water was spilled into it. I was told there was quite a bit of smoke coming from it right after the mishap, but fortunately there was no fire. Unfortunately, however, the phonograph was destroyed because of the damage to the amplifier. These small phonos may not have been worth repairing, even in the '40s-'50s, due to the sheer simplicity of the amplifier circuitry; I don't think there was much to these except the tube, a filament dropping resistor (if an amplifier tube other than a 117Z3 were used), a selenium rectifier, the loudspeaker of course, and the volume control with an AC switch on the back.

BTW, speaking of the 117Z3 tube, how many one-tube phonographs used this tube as an amplifier, with a selenium rectifier? I asked this question earlier in the thread, but it was never answered. I would think that phonographs using the 117Z3 would have almost ridiculously simple amplifier circuitry consisting of little more than the tube, volume control and a speaker. Talk about an electronic circuit in which almost nothing can go wrong! The only thing that could really go wrong with these, I think, is that the tube would eventually burn out or short.

Were the phonos with the 117Z3 among those that required a high-output cartridge to get any kind of volume? If a cartridge with an output on the order of 2 to three volts was needed to drive the tube to usable volume level, the 117Z3 (and probably most other tubes used in one-tube phonograph amplifiers) must not have been a very powerful amplifier to begin with.

I just looked on the internet and the 117Z3 is a rectifier tube only. IIRC, I have seen this tube used in some 3-way portable radios. The 117Z3 was only used when the set was run on AC power. I did find a 70L7 tube on the internet that is a combination rectifier and audio output. I can visualize this being used in a phonograph. Those little one tube amplifiers are not very powerful. The amplifier tube does not have enough gain when used with low output cartridges. That's why they used high output crystal cartridges. These crystal cartridges are almost always bad and there is a good chance that even a NOS one is not any good.

I have a Califone 1410 tube record player made in 1970 that has a transformerless chassis. The tubes are 50L6 and 12AV6 and the rectifier is a silicon diode. I had a Newcomb once that was transformerless. It used two 50L6's in push-pull and a 12AV6. The rectifier was also a silicon diode. The rest that I have seen all had power transformers. Was that Califone you had one of those big monsters with the speaker in the lid? I've got a Newcomb like that and it has some power to it.

[Old1625]

The one-tube phonographs sometimes used the 70L7, and sometimes used the 117L7 to dispense with the filament dropping resistor. http://www.nj7p.org/Tube4.php?tube=117L7GT IIRC the 70L7 could output considerably more than the 117L7, and they both differ in basing.

[Jeffhs]

Originally Posted by radiotvnut

I just looked on the internet and the 117Z3 is a rectifier tube only. IIRC, I have seen this tube used in some 3-way portable radios. The 117Z3 was only used when the set was run on AC power. I did find a 70L7 tube on the internet that is a combination rectifier and audio output. I can visualize this being used in a phonograph. Those little one tube amplifiers are not very powerful. The amplifier tube does not have enough gain when used with low output cartridges. That's why they used high output crystal cartridges. These crystal cartridges are almost always bad and there is a good chance that even a NOS one is not any good.

I have a Califone 1410 tube record player made in 1970 that has a transformerless chassis. The tubes are 50L6 and 12AV6 and the rectifier is a silicon diode. I had a Newcomb once that was transformerless. It used two 50L6's in push-pull and a 12AV6. The rectifier was also a silicon diode. The rest that I have seen all had power transformers. Was that Califone you had one of those big monsters with the speaker in the lid? I've got a Newcomb like that and it has some power to it.

Thanks for the information on the 117Z3. I should have known it was just a rectifier since the tube only has three elements, including the filament. The 70L7, however, is a new one on me, even after 40-some years of electronics experimenting.

My Newcomb phonograph had its front-facing speaker mounted in the cabinet; nothing in the top cover that I can remember--in fact, I don't think I ever had a cover with it since I got it. I do remember Newcomb phonos with huge external speakers; we had a few in the elementary school I attended as a kid in the '60s. Nevertheless, my own Newcomb phono had a very powerful amplifier. Wouldn't have wanted to run it wide open in the summer with the windows open (I still lived in a house at that time [early 1970s]; I'd really have a mess on my hands, however, if I ever played anything that loud in the apartment in which I live today). The neighbors probably could have heard it for blocks around at full volume.