I was watching A Christmas Story over the Christmas Holidays. It is kind of a tradition for me even though I have seen the movie several dozen times. Fot those of you who have not seen it, I highly recommend you take a look. Not sure how the humor would translate into other cultures.

Anyway, in one scene Ralphie, our protagonist walks up to an old full sized vacuum tube AM radio and presses a button on the tuner to select his station.

Now I am not old enough to remember these old sets but I do remember the mechanical push buttons on car radios.

My question is how did they work? I was thinking it might be based on a load on a spring but after thinking about it not sure how that would work.

So for the forum members that remember these old radios, did you ever have to repair the tuning mechanism? If so how did they work?

 

The buttons you are referring to were radio station presets. As I recall, these buttons were purely mechanical in nature. Each button could be set to a given radio station. By pressing the button (which took a bit of pressure as I recall, the tuner mechanism was moved manually to the preset station.

To set one of the buttons, you would turn the manual tuner to the station you wanted to setup. You then pulled outward on the button you wanted to set to the station and then press it back in. That would mechanically assign that button to the station you had chosen.

hgmjr

 

The buttons you are referring to were radio station presets. As I recall, these buttons were purely mechanical in nature. Each button could be set to a given radio station. By pressing the button (which took a bit of pressure as I recall, the tuner mechanism was moved manually to the preset station.

hgmjr

Yep that is them. I was trying to figure out how that pressure translated to a specific area on the dial. I do remember to set them you would tune to the spot on the dial. Pull the selected button out then push it in again to set it.

 

Yep that is them. I was trying to figure out how that pressure translated to a specific area on the dial. I do remember to set them you would tune to the spot on the dial. Pull the selected button out then push it in again to set it.

BINGO!!!!!!!!!!!!!!!

hgmjr

 

They used either a rack and pinion on each button or a cable/string to the tuning capacitor. Couldn't find the cable type in a quick search but here's a link to a rack and pinion set up. http://www.classicwireless.btinternet.co.uk/gecj.htm

 

I remember an old car that I had. The procedure was tune to the desired station, pull the button out and push it back in that would set that button to that station. I also remember car radios that were hybrid- with vacuum tubes.

 

A little off of the original question, but anyone remember the car radios that had station search? Hint: They used slug tuning.

 

I'm old enough to remember some of these sets, but not all. This sort of gadgetry began appearing by the later 1930s!

Many sets used the sort of mechanical systems described, but there were in fact several systems in use. Some were quite simple, using lever and springs working against mechanical stops adjusted by the user. This was fairly common in somewhat later car radios, often using a permeability (coil) tuner that naturally has a sliding action, rather than a rotary variable capacitor.

Some of the fancy mains sets used an electric motor to turn the dial to preset positions where the motor would stop.
Very impressive to see, but perhaps not so reliable.

A less exciting pre-set tuning method was used with some valve (tube) home radios. A set of push-buttons (or sometimes a rotary switch) switched out the normal tuning capacitor, and replaced it with pre-set trimmer capacitors. Normally these sets were superhets, requiring two capacitors per station. The user, or perhaps a technician, would have to tune in each station by setting the oscillator and aerial tuning for each one. Not the most user-friendly arrangement, especially as the tuning might drift.

 

Here in Australia the top of the Toyota range Crown had an auto tune radio in the late 60s. All i can remember is you pushed a button & the tuner was driven by a motor un till a selected station was found. Was pretty Cool in those days.

 

The system I had in mind used a solenoid to pull the tuning slugs to the low end of the dial, then release it. A spring mechanism with a governor allowed it to slowly return toward the high end of the band. When the AVC signal was strong enough, it would apply a stop mechanism at the station. If you didn't want that one, simply touch the search button and it would continue toward the high end of the dial until the next station was found.

 

To add to the user's joy, this little marvel had a LIVE CHASSIS, and was built for operation 240V AC/DC!

http://www.radio-workshop.co.uk/cgi-bin/album.cgi?picture=graphics/bush-dac10-01.JPG

http://www.radio-workshop.co.uk/cgi-bin/album.cgi?picture=chassis-pics/bush-dac10-02.JPG

 

It looks like the manufacturer at least mounted it in the case with insulated isolation bushings. Hot chassis units were very common in the US also. If you had the plug in the wall the right way, chassis was grounded, otherwise, you could get a good jolt, especially if one of the plastic knobs was missing.

 

I remember trying to figure out how a broken tuning string was put back on.

How the new digital radios in the 80's were pretty awesome for performance, everybody thought they'd suck.

In the 80's, everything had to be "DIGITAL", even analog clocks had a bunch of little flaps that would roll over to show the new time as an actual number instead of a dial moving around the outside. As many gauges as possible were changed to a number readout through analog means.

Now that everything IS digital, people are trying to make the analog look using digital parts.

 

There is a very good reason for analogue displays on a screen, as they are easier to read quickly at a glance. Thats the reason aircraft screen displays have analogue displays.