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

[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.