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GE Clock Radio Model 660
What have I done? I've started a third project while the two before it are unfinished of course!
Model 660 'Convertible' Many many years ago, when I was just a wee lad, I bought this pos from a garage sale, as I had many other radios. It still fascinates me. I still haven't seen that many clock tube-radios, and this one has a really cool feature: you can detach the radio and use it as a portable! I dunno, I think that's the coolest thing in the world. Lately, the box that it's been in for the past 10+ years has been relentlessly staring at me, so that's why we're here. This radio has seen some chaos, let me tell you. I think this set has had a lot more than a fall off the table in its life, I think somebody used it for a hockey puck. On multiple occasions. But that's for another post. The radio is a 4 tube battery-powered AM radio, and the clock is the radio's power supply (although it has no method for charging the batteries). At first startup, I did take it up to voltage slowly on a variac. As it was, the radio turned on, and did nothing but buzz loudly. The volume and tuning knobs made no difference. All the tubes test good and the power supply gave 67ish and 3ish volts (same as battery requirements). Given that there's only 3 not-ceramic capacitors in the radio, and another 3 total in the power supply, I just figured I'd go ahead and recap them. I recapped the radio, and there was no difference made. I recapped the PSU, and it did something! Now the radio buzzes very quietly, and the volume knob seems to have an effect - I can adjust the buzz from almost silent to very quiet. And also, playing with the volume makes static once in a while like a dirty volume pot would, so that appears to be working. The tuner still does nothing at all - however, if I touch the radio or PSU chassis, it changes the buzz noticably. If I touch one end of the antenna with a screwdriver (that I'm also touching) it sounds almost like it wants to pick up something, but that's probably because I'm touching it. Now... there is a slight possibility that the tubes are mixed up... I was very young. But I feel like I'd remember that. Like I remember pulling all the tubes out of my Zenith and not knowing where they went. (That'll be an upcoming project btw.) And there's only a stain where the tube map used to be, so fml. Also, while I was recapping the PSU, I think I might have gotten a resistor a little too hot (for an old resistor) but the output voltages still read the same. Ideas? Pics or didn't happen: Radio Bottom Before Radio Bottom After Radio Top PSU Before PSU After Last edited by MadMan; 01-21-2017 at 12:35 AM. |
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I had one of these when I was a kid too, in the 1970s. Mine was a sort of mustard yellow color. The filter cap finally went on mine and I just used the clock. It has three clear plastic knobs on the clock that are missing on yours.
Here is the schematic and parts list and tube diagram, on Radiomuseum: http://www.radiomuseum.org/r/general_el_660.html You can download up to three documents a day. I just downloaded three and they're very clear scans. You might want to move the leads of the caps you replaced a little farther apart. One cap's lead looks like it's touching another cap. Might be an optical illusion, but I thought I'd mention it. Amazing how much smaller the caps are. Your tubes, from the diagram, are 1U5 at the bottom, right above that is the 3V4, then to the right is 1U4 and at the very top is 1R5. That's probably the tube that's causing the problem since you have audio. The 1R5 is the oscillator-mixer tube. You may want to clean the tube sockets. I remember my radio like this being very microphonic, in that jarring it created all kinds of odd noises sort of like a xylophone. You're not old enough to remember Tom Terrific on Captain Kangaroo, but it sounded like the sound effect used on that. Good luck on your restoration. |
#3
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It's possible the 1U4 and the 1R5 are reversed, so you'll get some noise when touching the antenna. When installing that type 'lytic, I use insulation stripped from scrap wire and small shrink sleeving. Makes for a neater job, instead of using electrical tape, but tape is better than nothing. It doesn't take much to burn out those battery tubes. Take voltage readings with the radio and power supply connected. The selenium rectifiers might not be putting out enough voltage. The B+ should be close to 90 volts, even though, on batteries it uses only 67.5 volts "B". I have one just like it. |
#4
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(That feel when these forums don't have a [youtube] BBCode.)
Suffice it to say (in text)... IT'S ALIVE! Boy, you guys both called it! The 1U4 and 1R5 were switched. That's exactly what it was, only those two. I'm happy to say it's working nicely, even sounds halfway decent (I also repaired like 5 big cracks in the speaker cone, so I feel good about that). I thought for a minute it wasn't tuning anything on the high end, so I consulted another radio only to find there are like no stations between 1100 and 1600. But actually, there is one at the very tippy-top that a newer radio could get, but this one can't. But it does tune everything else on down. Oh well, I consider this little quirky radio to have made a full recovery nonetheless. Thanks guys! I finally fixed something! (That I've posted here lol) Quote:
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Actually, it reads 65v, so maybe the recitfier is weak or something, but it's still more than enough to make it work, which it is currently. Btw, fun fact, I have the original B battery, like the exact same one in the photo on the diagram. Last edited by MadMan; 01-22-2017 at 12:52 AM. |
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Also, I discovered the radio has a bad IF transformer, crackling, low sensitivity. I had it working fine about 10 years ago, replacing the 'lytics in the PS unit. |
Audiokarma |
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My clock also broke off the front cover. It has 4 protuding nubs that the screw go into, and all 4 were broken off AND the front cover was cracked almost in half. Happy to say that a lot of glue and elbow grease has fixed all that. Will do a post with pics of all the 'body work.' And yeah, apparently the PSU's giant waxy cap is a common problem. I imagine it was a cheap capacitor even when it was made. Come to think of it, it's not even branded. The little waxy one in the radio was - 'Planet' - and that was probably ok. |
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I can't pull up the schematic on my (Linux) rig, but am curious as heck about that series/parallel filament wiring. Presumably it's running from B+ thru a dropper. If so, then if one string goes open, then the other string will have twice the voltage on it. A zener would be great for protection, but there were no zeners when the radio was made. Just bein' curious.
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Old_coot88, If you have the Beitmens radio guides,its' in the 1955 book page 38. All the best, Tom.J
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#9
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MadMan wrote: Clear? Wow. Yeah, I never had the knobs. This thing was so abused. Clear, huh? I wonder if I could get some clear rod stock... maybe a horizontal blinds adjustment thingy rod? Cut knobs out of it and polish the ends. Hmm.
They were very much like mini-blind rods, clear plastic with ridges all around the edge, but solid on the front and they had a slightly raised pointer ridge, but you could just paint a line on the knob. What would be hard is to get the hole in the back right with the divider in it. Those shafts are split and the knob would just spin without the divider. The clock even has a sleep timer for the radio, which was a high-end thing in the 1950s. It didn't have a snooze control, though. I wish I had mine to take a picture. It was in great condition on the outside, but the clock worked long after the radio quit and I loaned just the clock to someone and I'm not sure I ever got it back. The tips of the hands glow in the dark, or mine did. That's great that you got your tubes in the right place and it works! I'm glad that's all it was. This design reminds me of the optional radio that came in the 1958 Oldsmobiles and Pontiacs, the Trans-Portable. It worked in the car or out of the car on its own battery. Last edited by jsowers; 01-22-2017 at 07:10 PM. Reason: fix quote |
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Audiokarma |
#11
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The PSU wiring was actually extremely confusing for me. They could've just had the double transformer, two selenium rectifier bridges, and maybe a capacitor or two, but instead they came up with this crazy contraption. Before I got the diagram, I actually drew my own just to see if I could make sense of it! The really weird thing is... they have a proper rectifier bridge for the filament power, and then they just use a tiny single diode for the (what I would consider much more important) 67.5v B+. I just... don't even. And actually, despite what the diagram says, the power coming 'out' of the transformer for B+ is actually 110v. It really looks like they put one diode in there to roughly halve the power, and cleaned up the oscillations with a capacitor and called it good. Come to think of it, maybe that's the reason that capacitor went bad in the first place. Quote:
Speaking of which, one of the shafts is damaged (and poorly repaired), so I'll have to make a replacement at some point. Quote:
And actually, I'm positive the giant waxy capacitor in the PSU was also bad before I replaced it. Last edited by MadMan; 01-23-2017 at 02:25 AM. |
#12
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On battery radios that have a single filament instead of a separate heater and cathode any hum on the filament is much more strongly coupled than conventional AC type tubes...As far as battery radio AC adapters go this is reasonably normal for the time...Granted many makers would cheap out and derive the A supply from a voltage divider on the B.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#13
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[QUOTE=MadMan;3177106]
HERE Aha. L'arn something new every day. All the battery portables I ever serviced used the B+ dropper for the 50ma. filament string. Quote:
If you felt like raising the B+ a bit, you could play with values of the voltage divider R13/R14. |
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I find it interesting that to make the series/parallel filament circuit function at 2.8 to 3 volts, the design wastes about 70 mili-watts by dropping 1.4 volts across the 27 ohm resistor. "A" battery life would have been better if the filaments would have all been in parallel, using the center tap on the 3V4 filament to connect it to the 1.4 volt source. The D cells could have been connected in parallel rather than in series.
jr |
#15
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While it's common today to put NiCad cells in parallel with no issues, I never seen it done with zinc-carbon cells back in the day. Maybe imbalance between cells mitigated against doing it.
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Audiokarma |
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