Okay so, I'm a software guy. I write software, I debug it and I support it. When it comes to electronics, I'm pretty clueless and if a problem can't be solved by re-soldering a connection then I'm stumped.. as is the case here. I'm really hoping someone can help me out because I'm about ready to start unsoldering random components just to see what happens!



Background:


I have a radio headset (actually a copy of the electronic hearing protectors made by Peltor etc) with a single pin 2.5mm Motorola connector on the downlead so that it can be attached to a radio. The headset itself has four internal speakers (two linked to left/right pickup mics.. lets say.. A and B, two linked to audio input.. C and D) and following this theme, it seems to have two independent circuits in it. The first controls the boom mic input, the on / off / volume controls and the left / right pickup mics, which are linked to left and right internal speakers (A and B). This requires a battery to work, and everything here is dandy. When the headset is connected to the radio, sound from the boom mic is broadcasted successfully.

The second circuit does not require a battery and should work like a regular pair of headphones. When the headset is connected to an audio input device (which should be a radio) the sound should be played back through a separate set of speakers inside the headset (C and D).



Problem:


The problem is, when the headset is connected to a radio, most sounds are not played back. No voice is ever heard over the speakers (C and D). Call tones or static can sometimes be heard, but they are garbled. With the headset connected to another device with a standard 3.5mm audio socket (it doesn't fit properly of course - you have to hold it in) such as an MP3 player, the sound comes through crystal clear. Why would this be?

I've been told that if you disconnect the right speaker (D) from the second circuit, so that only the left speaker (C) was connected to the audio input, everything is fine although I haven't tested this yet. If the right speaker was faulty, I wouldn't hear anything through it with an MP3 player connected, right?

 

In the absence of anything better to do, I unsoldered the right speaker and hey presto it works.. perfect sound through the left speaker. I salvaged an old speaker from some PC headphones just to test things out and soldered it in place of the right speaker and I get sound through both. Unfortunately the speaker from the PC headphones is too big to fit inside so it can't stay there.

But since I have two of these problematic radio headsets I thought.. ah ha! I shall steal the "good" speaker from the other set, put it in this one and then I will have one fully functioning headset. Wrong! It seems like if I have two of these speakers wired up to the circuit, neither works properly. But if I only have one (either one) it works fine. Maybe the impedance for the speakers is too high (when combined) for the signal from the radio.. which is weaker than the signal from the MP3 player which plays fine through both speakers? I'm really just making wild guesses here..