"Last gasp" GE tube/transistor hybrid clock radio
 

Tonight, I dug out this GE AM/FM-AFC tube/transistor hybrid clock radio. On the front, it says "solid state tuning". I can't find any visible date codes without removing the chassis and the model tag is too faded to read; but, it looks very late '60'ish to me. It plays pretty good on AM; but, FM is not that great unless it's a strong local station. Anyone remember these?

http://i538.photobucket.com/albums/f...kradio0001.jpg

http://i538.photobucket.com/albums/f...kradio0002.jpg

That "68-5" stamped on the clock motor is probably a date code. I wonder what they meant by "solid state tuning" - from the pic I don't see anything but an ordinary cheaper AM/FM set.

What kind of FM antenna does it use?

I see a couple transistors down there by the tuning cap.

Maybe that fur down there by the green transformer? (Just teasing radiotvnut, blow that dust out of there, will ya? I keep having to resist the urge to blow on my computer screen!)

Seriously though, maybe it's one of those jobs that uses the AC line for the antenna. Looks like some good-sized disc caps on the AC input plug.

--Bob

I think it does use the line cord; but, I attached a length of wire to the FM antenna terminals because the line cord was not cutting the mustard. One day, I'll pull this apart and try to improve it's FM performance. Really, the only reason I've kept this radio is because of what it is. I think this is the only AC operated consumer radio that I've seen that used both tubes and transistors.

It's funny that I didn't notice that date stamp until you pointed it out. And, yes, there are at least two transistors close to the tuning cap.

I see them now! I agree, it's very unusual to see a "hybrid" radio, but if anybody did it GE would.

I've seen these before but never realized that they were a hybrid set. Whats the tube line-up in it?
-Tony

What shocks me is that GE didn't use a compactron tube or two in this set since they were so hung up on them. I have got an Audiotronics AM/FM "classroom" radio that uses a compactron (6T9) as an audio driver and output tube. The other tubes are regular 7 and 9 pin miniatures.

There were a few battery operated hybrid radios made in the '50's. Most used transistors in the audio output stages while subminiature tubes were used in the rest of the circuit. And, let's not forget about the hybrid auto radios from the late '50's and early '60's. You know, the ones that used low B+ tubes and a big audio output transistor mounted to the rear or the side of the radio.

Clean the tube sockets and the usual spots and you might be surprised how much better it gets.

It is rather nice! I like the way "lighted dial" is advertised on the face as a feature !
The 3 blue electrolytics are a bit of a shock to the eye.

The clock mechanism looks just like the no-longer-working timer thing in my mother's oven!

That's a Telechron movement. Very easy to fix if broken, as the coils and capsules are replaceable.

I would be very curious to see the actual explanation from the schematic or service
data, but looking at the mechanical variable capacitors with a small number of plates,
I would assume that FM tuning is conventional while AM tuning uses the transistors,
and possibly a varactor diode or two. Anyone got more info about this funny radio?

I have several of these radios...the FM RF, mixer and oscillator stages are transistorized and on a separate little circuit board which mounts on top of the main one. The AM tuner is a conventional 12BE6 tube and the rest of the circuit is just a conventional tube radio, 2 IF stages and solid state diodes for the FM ratio detector.

Do you have a model number for this radio?

I have a AA5 GE clock radio that is pretty common but it took me forever to figure out the model number. Do other GE radios have the model number on them? Do they just get lost with time?

John

I see. So 'solid state tuning' does not mean that they are dispensing with
the mechanical variable capacitor. A bit like early automotive electronic
ignition setups that were still using the breaker points, if I understand
correctly.

Tube FM front ends tend to go bad easily, if the tube gets a little low on emissions. Also many such AM/FM sets tended to spend most of their life on AM, and the FM tube would go bad due to "sleeping sickness" (the cathodes being hot but no current being drawn does bad things, but a few tens of microamps of current is enough to prevent that, connect a 100K or so resistor across the B+ part of the band switch on such an all tube radio, not this one though). But the transistors won't have this issue. But transistor FM RF front ends did suffer easily from signal overload, intermod products creating interference on weaker FM stations (though I've been told that increasing the current thru the RF transistor will help). Living 14 miles line of sight from NYC's Empire State Building's FM broadcast antenna farm brought this issue firmly in my face... Tube front ends usually did better on this.

Tube line up is probably like that in an AA6 AM radio, but the extra 12BA6 being the 2nd FM IF tube (and it may be a 12AU6). If they were skillful enough, they might have been able to put that 2nd FM IF tube to work as an AM RF stage, like in most AA6's.

Not using a tube FM front end meant that they would have enough heater string voltage left to use a 35W4 rectifier. Which might have been cheaper at the time than a SS rectifier diode.

GE used the same or quite similar audio output transformers in their solid state hot chassis radios as well.

Looks like typical GE build quality...

It's a nice clock radio, well preserved, too, and does what it's supposed to do. But consider the power of advertising: it proudly announces "Dual Speakers." Wow, that must be better than a radio with one speaker. It's kind of like a stereo, isn't it? Let's buy this one. Bingo.

The fact that one or two or three or six 4" speakers still sound like...guess what? a four-inch speaker, with the same frequency response, does not matter.

G.E engineers knew that in that same size case they could have got one 4 x 6" or even one 5 x 7" speaker and had much better sound, with a little inkling of bass, but with the clock moved over to one side of the front, and maybe for the same cost, but then they couldn't have advertised Dual Speakers! The Advertising/Marketing Department won out, as they usually do.

Then again, I'm sure 4" speakers were churned out in greater numbers than any other size, and cost next to nothing. So the Bean Counters had the last word, too.

Just some observations on manufacturing.

Reece