Introduction: Transistor Radio Time Machine

Don't throw away that old transistor radio! Re-purpose it into a time machine with strange, nostalgic broadcasts through the original speaker. Complete with a choice of custom time-destinations and fluttering amber light reminiscent of old tube radios. Makes a great gift with a surprise inside and no exterior signs of modification.

Skill level: Medium. No computer programming necessary.

Time: First one takes about 8 hours, then about 4 hours each once you get the hang of it.

Green: Recycled broken radio, re-purposed LED's and batteries from tea lights.

Materials cost about $13.85 including batteries.

Step 1: Tools Required

To build your amazing time machine, you'll need the following tools:

1. Scissors
2. Medium flat-head screwdriver
3. Small "nibbler" wire cutters
4. Small needle-nose plyers
5, Small flat-head screwdriver
6. Small phillips-head screwdriver
7. Soldering iron
8. Glue gun (optional)

I also used a small coping saw for flat cuts that were difficult with the rotary tool.

Step 2: Parts List

To build this amazing time machine you'll need:

1. An old, broken transistor radio. This Instructable is for a side-dial thumb wheel model, but you can build one with a center-dial unit too by getting creative with the switch and LED placement.

2. A sound card that records and plays back audio. For this project, I used a dual-sample circuit board from Electronics 1-2-3 that costs $7.55, here's a link: .

3. Two LED tea lights that flicker with an amber glow.

4. Solder and solder remover or wire braid.

5. An eight inch length of 9-conductor ribbon cable or equivalent. Easily removed from any broken computer. I like the rainbow colors for easy wiring and a pretty look if someone opens the case.

6. Two 3-Volt CR-2035 dime batteries and holder. You can sometimes re-use the batteries that came inside the tea lights, as well as the battery holders if you want to trim them down and connect them together in series for 6 volts. Otherwise, good prices on eBay. You could also go with the original 9-volt battery instead and put in a voltage regulator circuit to bring it down to 6 volts. I chose to keep things simple as the current draw is minimal.

7. One 3/4 inch nylon bushing or two washers glued together for greater thickness.

8. Goop or Shoe Goo brand adhesive with applicator tip cut to smallest opening.

9. Electrical tape.

10. Masking tape.

Step 3: Open Case

Locate the rectangular opening tab usually at the bottom of the case. Using a medium flat-head screwdriver, gently pry open the case to reveal the components.

Step 4: Remove Circuit Board and Speaker

Remove screws to free up circuit board and speaker and take both out of the case.

Step 5: Grind Radio Circuit Board

Find a place on the thumb wheel tuner dial that does not rotate do the outside area where it will come in contact with the operator's thumb when turning. Mark that spot with a pencil, then turn the dial and select two places on the circuit board to install the switches.

Using a rotary tool, grind off the solder and copper clad from circuit board at the two locations.

Step 6: Remove Switches From Sound Board

Locate the two switches on the sound board and remove them using a soldering iron and solder removing braid. You might need to gently pry them loose with the small flat-head screwdriver after the solder is removed.

The switches are slightly oblong rectangles so choose a side where two of the leads are closest together and clip them off leaving the two leads on the opposite side intact.

Step 7: Glue in Switches

Apply the Goop or Shoe Goo adhesive to the areas on the circuit board you ground flat, then place switches in the glue with the side that has the remaining leads facing upward. The round buttons should face the tuning wheel with a piece of thin cardboard in between them both to create a small gap. I used some cut-up pieces of the battery packaging.

Then apply more adhesive to the backs and sides of the switches being careful not to glue the button part so it won't press. Be sure to leave the two contact leads exposed.

Apply some masking tape to hold the switches in place for 1/2 hour, then remove it as well as the shims and let dry overnight.

Step 8: Connect Sound Board

Locate the sound board and ribbon cable. Solder the individual leads of the ribbon cable to the sound board. You may find the following color coding useful for later reference:

Red: V6+ (Positive voltage in)
Black: Ground
Brown: Speaker pin 1
White: Speaker pin 2
Blue: Switch 1, terminal 1
Green: Switch 1, Terminal 2
Yellow: Switch 2, Terminal 1
Orange: Switch 2, Terminal 2

With the relocation of the switches adjacent to the thumb wheel, you can start to see that this you are merely creating jumpers for the switches themselves.

Cover the bottom of the circuit boards with electrical tape and trim the sides.

Step 9: Connect Speaker

Remove the wires connected to the speaker.

Locate the brown and white wires coming from the sound board and solder the remaining ends of the brown and white wires to the two terminals.

Step 10: Connect Battery Holder

Locate the battery holder. You may have to pull the metal positive "+" contact arm out with your needle nose-pliers to accommodate the two batteries stacked together like pancakes to total 6 volts. Test your fit.

Cut and strip an eight inch length of both red and black wire. Solder the red wire to the positive "+" terminal. Solder the black wire the the negative "-" terminal as well as the black wire that is connected at the other end to the sound board.

Fold back the terminals so they are flush with the bottom and cover them with electrical tape.

Step 11: Hook Up the Thumb Switch

On most older transistor radios, there is a second thumb wheel that controls on/off and volume. You can hear a little "click" as you rotate the wheel to engage the switch. We're not going to use it for volume because the impedance of the radio potentiometer is usually not a good match for the new sound board. Anyway, the sound board puts out just the right amount sound for the speaker. Locate the two outer terminals of the potentiometer/switch that is attached to the thumb wheel and confirm that they are connected to the switch. On one of the two terminals, solder the red wire coming from the battery holder.

Cut and strip an 8 inch piece of red wire and solder it as well as the other red wire connected to the sound board to the remaining terminal on the thumb wheel switch.

Step 12: Disassemble Tea Lights

This part is usually easy, depending on what kind of tea lights you use. Some have separate little circuit boards that make them "flicker" and others have that built into the LED's themselves-- that is the kind I like to use but the others will be fine if you have room for their circuit boards.

Using a small flat-head screwdriver, pry the bottom out of the tea light.

Remove the battery

Bend the leads beneath the batteries to release the LED lead.

Turn over and unsolder the other side of the LED from the switch.

Do this on both tea lights to remove the LED's.

Step 13: Solder the LED's

You'll notice a flat spot at the base of the LED's. Take one of them and solder the black wire to it that is attached to the battery holder at the other end.

Now solder the remaining lead of the LED you are working with to the other led on it's side with the flat end. You are creating a "series" circuit so the two 3 Volt LED's combine to make a 6 volt circuit that can handle the power.

Solder the remaining lead of the second LED to the red wire coming from the thumb wheel switch.

Wrap the exposed leads of the LED's with electrical tape.

Step 14: Install Nylon Crescent

Cut a small "half-moon-shaped" crescent from nylon bushing.

Locate your original pencil mark on the tuner thumb wheel. Using the rotary tool, flatten the edge of the wheel to match the nylon crescent.

Glue the crescent to the flat spot of the wheel.

Let dry.

What you've created is a "bump" on the wheel that engages the switches as it passes them. This way, you don't have to install modern buttons on the outside of your old radio.

Trim the "bump" with the rotary tool for the right width so it engages the switches without pushing them out of position.

Step 15: Solder Wires to Switches

Solder the leads coming from the sound board to the switches as follows:

Blue and Green to Switch #1

Orange and Yellow to Switch #2

Step 16: Remove Radio Parts

On the original radio circuit board, use your "nibbler" wire cutters to cut the leads of the electronic parts at their base to remove them. This will leave a flat surface to glue your components to.

Step 17: Glue Components

Install the batteries and put a little glue around the double-stack of them to secure them in the battery holder. This glue peels off easily for battery replacement.

Glue the circuit board and battery holder to the radio circuit board (the side without the thumb wheels).

Test-fit the back cover to make sure there or no blocked screw holes or obstructions to closing it up.

Step 18: Glue in LED's

Turn the radio circuit board over to the thumb wheel side. Turn the thumb wheel switch to make the LED's glow and glue them in place. If you point them toward the case slots that the thumb wheels poke out of, you'll get a flickering old-time tube radio glow through them. The thin plastic cases will sometimes allow a little of the light through as well. Some radios allow you to point the LED at a transparent dial which reflects their light to the outer ridges and looks fantastic! Experiment with different angles for the best effect.

Step 19: Re-assemble

Install components back in case and check for obstructions and free spinning of thumb wheels.

Re-insert screws to hold circuit board and speaker in place.

Step 20: Record Time Travel Broadcasts

You can search for recordings of old radio broadcasts all over the internet. Youtube has a few, and here's a link to some more:

Slide the switch on the sound board to the "REC" position to record.

Cue up the sound you want to play from your computer, and position the radio about six inches from your computer speaker set to play back at conversational volume.

Turn the tuner thumb wheel to engage one of the switches and hold it there until you want it to stop. It will allow a little over 20 seconds maximum for each recording.

Now cue up your second audio message on your computer, turn the thumb wheel to engage the second switch and hold to record.

Step 21: Time Travel!

Slide the switch on the sound board to the "PLAY" position.

Replace the back cover of the case and snap into place.

Turn the thumb wheel to engage either switch to play back your sounds and travel through time!

Step 22: Epilog

I've made a few of them and it gets easier and funner every time! If you really want a challenge, try using one of the old "micro-mini" models like the one pictured in a poster that I got when I bought one. I love the old "princess box" they came in!

If you are making your Transistor Radio Time Machine as a gift, here's a few suggestions to make it special and specific to the recipient:

  • Find out their birthday and date. Record yourself speaking as an old-time radio news announcement about the day of their birth and how very important it is.
  • Find and record a sports game highlight of their favorite team on the year they were born.
  • Record a pop tune they used to love as a child.
  • Find an old ad of a product brand that is still made that you know they use.
  • Record a hint for a treasure hunt.
  • Record your voice doing an impression of them talking to themselves from the future.

After receiving one in the mail my friend Simon had this to say:

"What is this, some sort of evil "Si-Op"? The radio is talking directly to me, and it KNOWS i'm LISTENING! Brilliant!"

Have fun, and please feel free to post your comments or questions here. I'm always looking for new ways to tinker with this stuff.

I make lots of interactive art, big and small, for the Burning Man art festival. Please check out my website at for other weird stuff.

Be well and do strange things!

-Mister Jellyfish
Epilog Challenge

Participated in the
Epilog Challenge