Cheap Signal tracing for troubleshooting radios

Don't have a signal tracer?
You can make one!

If you have a pair (or single) high impedance headphone set, you could use it, with a small signal diode and a capacitor for safety as a signal tracer.
You will need to do some measurments in order for the assembly to fit inside the New pen probe.
You can use the barrel of a BIC ink pen or other brand that has no metal. Its all plastic, which would insulate you from shock. If you have an old RS232 plug, there are a number of pins that you could salvage for the tip of your probe. Remove and solder a very short piece of wire to the pin. Add to that wire a small cap and then a diode in series, and then add a long wire. Solder all.

Remove the ink barrel and insert the new pin assembly into the empty pen. with the metal pin slid into the pen down to the tip, expose the pin so it will act as the probe tip in the same area as original ball point. use RTV or other glue or epoxy to hold the pin in place. Your diode and cap should fit inside the pen barrel. Use RTV or Epoxy to the secure the wire coming out of the pen. (I personally would use covered test lead wire, as it is the most flexible.)


Take this long wire and connect it to one of the earphone connectors. Take a similar wire and add a alligator clip to it on one end. This will be used to clip to common ground or chassis. On the other end of this wire, connect it to the remaining connector of the Earphone.

For trouble shooting Start at the radio speaker and Trace the audio signal back that way.
Keep one hand in your pocket to prevent shock.You can use a probe Or your finger tip to see if the volume control is working by Touching the center tab and see if it causes a hum in the speaker, if not the audio section is suspect.

If you get a sound then use your new probe to do probe the previous stage for an audio signal. If you lose the audio signal then investigate for faults in (components, wires, traces,solder connections, mis-wiring etc.) in that stage. If you get a signal then go to the next previous signal.

Happy signal hunting
It will help you fast to isolate troubles.

Cliff Hanger
Nice Idea on the home made signal tracer.
But is there any chance you could do a picture, diagram or scketch. Its a little hard for me to visualize the end result from the description. Also i am the proud owner of an audio generator ElCO i think. Could i use that to do the same thing?
Joe from Holy Toledo