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IS THE DC VOLTAGE DETECTED ON SPEAKER TERMINALS ARE NORMAL? LIKE 24 VOLTS DC?
A loudspeaker doesn't usually have DC present on the terminals due to the very low impedance a high current can flow and destroy the speech coil. It would also hamper the correct operation of the loudspeaker.
Because of this the amplifier output is decoupled either by transformer or by capacitor, effectively blocking direct current while allowing the alternating current output of the amplifier to pass.
The thump sound in the speakers at switch on is caused by the decoupling capacitors charging due to the speaker providing a ground path.
Purely as a matter of interest, in the days of ancient radio, some speakers had no magnet which was replaced by an electromagnet through which the radio supply current would run after rectification and smoothing, the windings acting as a smoothing choke providing additional regulation. Such loudspeakers had four terminals, two of which did carry a powerful direct current and those confusing the terminals quickly saw smoke...
Car Audio &...
on Jun 12, 2020
My stereo KDC U3556 SHOWING PROTECT
It's protecting itself from a wiring short. There is a way to reset it but I can't remember the two buttons you hold down. I remember that first you have to disconnect the power and before turning on you push and hold two buttons the 3 and 6 continue holding when you power on radio.
Car Audio &...
on Jun 09, 2020
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