Olympic 447 transistor radio from '56

[radiotvnut]

Here's an Olympic model 447 4-transistor radio from circa '56. If you're a small company in the mid '50's and want to get on the transistor radio bandwagon, what do you do? Simple, you take your existing 4-tube portable radio, modify the circuit to use transistors, and mount the transistors in the tube sockets that were on the original tube chassis.

I have not yet tested this radio; but, I'm sure it won't take much work to get it going (assuming that the germanium transistors are good).

[dieseljeep]

Originally Posted by radiotvnut

Here's an Olympic model 447 4-transistor radio from circa '56. If you're a small company in the mid '50's and want to get on the transistor radio bandwagon, what do you do? Simple, you take your existing 4-tube portable radio, modify the circuit to use transistors, and mount the transistors in the tube sockets that were on the original tube chassis.

I have not yet tested this radio; but, I'm sure it won't take much work to get it going (assuming that the germanium transistors are good).

I was amazed how well those early four transistor radios worked and sounded.
I had an Emerson and a GE. The GE was a little more desirable, as it used four size "D" flashlight cells, instead of the expensive nine volt packs.

[Sandy G]

I don't have MANY Soiled-State sets, but I could EASILY find a place in my heart for THAT one..

[Dave A]

What would it take to do that today with an old tube plastic radio like the Olympic? Transistor types? Battery mods? I'm thinking of my GE version of that radio.

I wonder if Olympic used stock and deleted power sucking parts to make it work. Snip, snip.

[radiotvnut]

I'm going to do a youtube video on it soon.

I also am going to try and find the tube version and do an in depth comparison between the two.

It would be interesting to take a junker AA5 and convert it to solid state.

[bob91343]

That is so funny! Of course using PNP transistors meant reversing polarity of the battery and any electrolytic capacitors. And reducing B+. I only see two transistors; weren't there four? And making the front end work, well that takes more than sticking a transistor into the converter socket.

[Username1]

That is a nice find there.... Are all the transistors in tube sockets...?
I guess for the day, maybe tube sockets were cheaper, and possibly
I bet the transistors were pretty pricy. I think many of the soldering people
could have over heated and burned out the transistors, So not soldering them
ensured more survived the assembly. And I bet the sockets made
salvage easy if they had one at the end of the assembly line that did not work.

Since they were hand soldered, and converted from tube sets, that means they had
4 or 5 extra tie points per section for wiring.....

I think that in depth comparrison would be a very interesting page..... Hope you can get
what you need to get it done....

Are the transistors slid into the socket, or soldered at the bottom....?
I know they could easily crimp the tube socket pin holders as needed.....
How did they do it..... are they crimped....?

I wonder if the audio output transformer has the same specs as the tube version...?
and if the part numbers are the same.....?

[davet753]

That's a very nice find! You must have a pretty rare radio there, as there surely can't be many of those floating around these days.

I have a few Olympic service manuals, but they're all television.

[radiotvnut]

I haven't opened mine yet; but, from others who have this radio, the transistors are soldered in place and all 4 of them are in tube sockets.

[radiotvnut]

I had a chance to check the radio and except for some faint speaker clicks when connecting power, the radio is dead. I touched my signal tracer probe to the base of the output transistor and got reception through the signal tracer; which, tells me that everything up to the output stage is at least working well enough to pass a signal. The germanium output transistor has an open B-E junction. The schematic calls for either a CK751 or GT751 (these numbers cross to a modern day NTE102). Now, let's hope the local parts house has one.

[Sandy G]

It'll be interesting to see how it compares in performance w/ an "AA4"...

[radiotvnut]

A new NTE102 audio output got the radio back playing; but, the driver transistor, also crosses to an NTE102, is very noisy (I knew I should have bought the other one that they had). With the signal tracer on the base of said transistor, there is no noise. With the signal tracer on the collector, it's noise city. With the signal tracer connected to the cathode of the detector diode, it's loud and clear. So, that tells me that the mixer and IF stages are in decent shape. Sensitivity isn't the best in the world; but, I don't expect a 4 transistor radio to be a station magnet and others who have this radio also say that it isn't very sensitive. Once I get rid of the noise, I will peak the alignment.

[wa2ise]

Originally Posted by Username1

That is a nice find there.... Are all the transistors in tube sockets...?
I guess for the day, maybe tube sockets were cheaper, and possibly
I bet the transistors were pretty pricy....

They probably had tons of tube sockets in inventory, the chassis punches as well, so they used what they had. The tube sockets also offered extra tie points as well.

[dieseljeep]

Originally Posted by radiotvnut

A new NTE102 audio output got the radio back playing; but, the driver transistor, also crosses to an NTE102, is very noisy (I knew I should have bought the other one that they had). With the signal tracer on the base of said transistor, there is no noise. With the signal tracer on the collector, it's noise city. With the signal tracer connected to the cathode of the detector diode, it's loud and clear. So, that tells me that the mixer and IF stages are in decent shape. Sensitivity isn't the best in the world; but, I don't expect a 4 transistor radio to be a station magnet and others who have this radio also say that it isn't very sensitive. Once I get rid of the noise, I will peak the alignment.

It's really amazing how well, some of these early designs performed. I mentioned the GE, I had years ago, a large portable with a 4" speaker and only four transistors.
It seems strange, that almost all the pocket radios had six transistors and their DX performance, wasn't that much better. I know that the loopstick was shorter and a few other issues. more later!

[radiotvnut]

https://www.youtube.com/watch?v=HLD8Fz7c1gA