You could power the receiver with the standard 9V battery. However, the short battery life will severely limit how long you make this prank work. So I designed a simple 9V power supply that will be able to power the receiver using the TV’s AC power line. With this power supply you can run the receiver indefinitely. Here is how to make it.
These are the materials that you will need to make a simple 9V power supply:
AC Adapter with an output of at least 9V DC
LM317 Variable Voltage Regulator
1.0 µF Capacitor
0.1 µF Capacitor
240 ohm Resistor (or two 120 ohm resistors)
1500 ohm Resistor for a 9V Walkie Talkie (for 7.5V use 1200, for 6V use 910, for 4.5V use 620 and for 3V use 330)
Assemble the parts on a small perf board according to circuit diagram shown above. Connect the AC adapter to the circuit’s V(in) terminals and you will have a 9V power supply that is capable of running your walkie talkie. For a more in depth discussion of this circuit and how you can assemble it, you can check out these two projects where I show how to make custom power supplies with a voltage regulator.
DIY Hacks & How To’s: Convert Battery Powered Electronics to AC
https://makezine.com/projects/pocket-sized-power-supply/