I recently dug out some Walkie-Talkies from a closet. Two Motorola TLKR-T3.
To my surprise, both do not have any sound in receive mode.
The problem would have been on only one device, I'd have thought about a bad soldering joint. But both have the same symptom at the same time. That makes me think it is a bad component. Something like a dry chemical capacitor or a bad electromechanical component (like a relay).
First step, opening one Walkie-Talkie.
There's a lot more components than I expected. But no chemical capacitor that looks defective. However, there a component that looks like a relay (3 pins on one side, 2 pins on the other side). This "relay" has drops of condensation on its surface. Drops that don't evaporate. That's suspicious. Let's dig on this side.
After much research on the WEB, I've finally found this component (CQ WM50HTC) is not a relay but a 450kHz +/- 3kHz ceramic filter used in radio receiver stages. The teardown of the component confirms this.
There is much oxydation inside the component. It is therefore probably out of order.
Of course, this component is not manufactured anymore. Hopefully, while searching the WEB, I found an equivalent one can buy on a well known WEB site. It's reference is LTM450HTW.
Once the defectie CQ WM50HTC have been replaced with brand new LTM450HTW, the Walkie-Talkies are working correctly again !