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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.

enter image description hereAnd if it is an inductance, what would be its purpose? At 140mH it seems far too large in an audio circuit.

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    \$\begingroup\$ I've definitely seen a question like this before asking the same component. \$\endgroup\$ – Bradman175 Jul 23 '16 at 3:52
  • \$\begingroup\$ Supplementary question: Given where it is, would it have the effect of mitigating a turn-on plop from the speakers? \$\endgroup\$ – user207421 Jul 23 '16 at 7:51
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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.

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  • \$\begingroup\$ +1 for not being fooled by the obvious. \$\endgroup\$ – Sparky256 Jul 23 '16 at 16:10
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It's a transient / surge absorber (google "ZNR"). Its purpose is to limit the inrush current caused by empty capacitors during power-up.

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  • \$\begingroup\$ Also known as PTC resistors or resettable fuses. \$\endgroup\$ – Sparky256 Jul 23 '16 at 6:02
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    \$\begingroup\$ Metal Oxide Varistor (MOV/ZNR) devices and PTC resettable fuses are two completely different devices that happen to look similar in some cases, so only one of you can be correct. I would tend to think it's @Sparky256 because they appear to be in series. \$\endgroup\$ – Spehro Pefhany Jul 23 '16 at 6:18
  • \$\begingroup\$ No, a PTC is the only resonable answer since they are in series. \$\endgroup\$ – winny Jul 23 '16 at 7:55

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