Adding Dial Light to an Old Clock or Radio
Most clocks and radios until about the 80s did not have a dial light. This meant you needed to turn on lights in the room to see what time it was.
Some manufacturers before the 80s offered displays that glowed in the dark like Sylvania's Panelescent displays. Most manufacturers offered clock arms that were coated in phosphorescent paint that glowed lightly in the dark. These phosphorescent coated clock arms stop glowing over the years.
Some manufacturers offered models that were truly lit with a neon gas bulb that stayed on with an orange glow as long as the device was plugged in. These models like Motorola C series from 1963, GE 913D from 1959, and Arvin 5R series from 1961 are rare because the gas bulbs were relatively expensive.
With modern LEDs, the capability of illuminating old clock and radio displays is now relatively inexpensive and straightforward. These typical LEDs have a rated life of 55,000 hours which about 6 years.
Here's a roller film clock that was made sometime in the 70s. It was not orginally designed with a lighted display.
Here's a roll of inexpensive LEDs.
This strip can be cut any length to suit your needs. It requires 12V DC to work.
These LEDs come with an adhesive backing which helps with installation. I found the adhesive backing is not very secure. More on this later.
You will need a 12V constant supply in order to power the LEDs. You can also use a non switching transformer depending how much space is available inside your clock or radio. The switching transformers are a lot noisier which is probably not as desirable if this is going into a radio.
Here's a picture of the LED strip wrapped around the clock display.
Here's two leads connected to the device mains line in. Be careful when you're handling these clock power input tabs. They are made of plastic and very fragile. The clock winding wire is as thin as a human hair. If these break, you may need to scrap the whole clock motor. Obviously, make sure the clock is not plugged in when you're doing this.
Here's a ON OFF slide switch installed on the clock back panel.
Close up shot of the LED driver:
Wiring the ON OFF switch between the power source and the LED driver so that the LED is not always on.
Finishing up the ON OFF switch wiring:
Let there be light!
Now off. See the difference?
Now, the tricky part of reassembly. Make sure the thing is unplugged. Be careful of those little clock tabs. You've been warned!
Here's another example of a typical clock movement from Telechron. You will find a lot of these in mid century clock and clock radios. This one is an extremely rusty example. But, it gives you an idea. This one is also missing its motor. See the little tabs protruding from the winding? It is wrapped in paper. The tabs have a tendency to rip off the winding core. Don't bother trying to rewind this thing if you break off the tabs. You might be able to find the broken end and reattach it to the tab. As long as the break is at the end, you'll be ok.
Trickiest part of this whole project so far has been the correct routing of the LED strip to maximize illumination without blocking the movement of the clock numbers. I had to use a few zip ties and some glue.
Finally, the end result is a 70s clock with modern LED lighting display that won't need to be changed for another 6 years! Yes, your other clocks with LEDs have the same 6 or so years lifespan before they too may go dark!
Here's a shot of the back:
Here's not lit:
Here's lit (again). See the difference?
Enjoy your tinkering!