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Kenwood SW-900 subwoofers circuit principle and repair

Time：2015-06-02 08:11:28 Source：Network Author：Unknown Clicks：11329

5. protective circuit
Circuit is shown in Figure 5.

Two types of protection: boot protection and neutral point voltage unbalance protection. When on, CPU ⑧ feet delay 4S +4.8V output voltage, the power indicator led D39 shiny, Q28, saturated hydraulic conductivity, and relay K2 release load disconnect when the midpoint voltage exceeds 1.5V, Q26, Q27 saturated breakover, Q28 b short circuit to ground, K2 released load disconnect.
6. Common repairs
(1) power supply does not normally cause a silent
± 12V power supply not working properly can lead to dual operational amplifier, analog switch IC, the sub woofer circuit is not working properly, resulting in silence. 44V powered abnormal machine does not work. So, when the silent, first to test the power supply voltage is normal.
(2) K2 relays are not
Major fault: CPU circuits are not working properly, or a bad connection; power bleeder R179 open; the midpoint voltage is normal.
(3) the preamplifier and sound processing circuit abnormal causes silent
If dual op amp IC1 or IC4 damage, will cause the audio signal will not be able to enlarge, also failed to pass. In addition, the D4066BC of damage will cause M5134P signals to go through D4066BC and enter the volume potentiometer.
(4) power amplifier circuit abnormal
From the volume potentiometer, the signal input to the power amplifier circuit for voltage and current amplifier and then push the horn sounds. Power amplifier circuit maintenance is the key measurement point voltage and current at the end of the base voltage of the amplifier. Normal Ub= 0.5V, the power amplifier circuit for class b amplifier circuit.

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