amplifieraudiopassive-components
I refer to the two round yellow-ochre things mounted on the blue capacitors. They are coupled in series from a sold-state power amplifier stage, and the capacitors AC couple to the speaker load. The mystery components appear to be inductors but they aren't featured in the schematic. They measure 1R3 and about 140mH.
And if it is an inductance, what would be its purpose? At 140mH it seems far too large in an audio circuit.
"Obviously these speakers have a much higher impedance than the amplifier is rated for, so could this be why the original amp failed immediately?"
NO it cannot. If it would be a problem then such an amplifier would also fail when you would operate it with no speakers installed. That would be plain silly. Audio amplifiers have a voltage output (low impedance) so only a very low impedance could cause it to fail. But almost all modern amplifiers can handle loads of 4 ohms or higher. Also, most modern amplifiers have some form of overload protection so it would just shut off.
OK, it appears there are four 16 ohm speakers in parallel. This would give a total impdedance of 4 ohms. That would be OK if the speakers are indeed 16 ohms. But if they are bit lower in impedance then the combined impedance will be below 4 ohms and for some amps this can be a problem.
A solution might be to instead of switching the 4 speakers in parallel, to make 2 pairs of 2 in parallel and put those 2 pairs in series. Then the total impedance will be around 8 ohms, that should not give any problems.
Can't be absolutely certain but the IC looks to be a TDA7052 (http://www.nxp.com/documents/data_sheet/TDA7052.pdf)
The bjt looks like a pre-amp stage for an electret microphone. Not totally convinced you have the correct circuit but there are lots of similar circuits out there on the net you could use.
for example:
Best Answer
I, too, would vote for PTC (Positive Temperature Coefficient - a resistor that increases in value as it warms). Used to limit inrush current. It may be these are an afterthought, which would explain why they are not in the circuit diagram.
A MOV is a surge suppressor that decreases in resistance over some limiting voltage. Used across lines to prevent excess voltage during faults.