Owner said this speaker recently appeared a strange phenomenon, after you plug in a USB flash drive indicator light flashes, once in a while the speaker has sound. Yesterday moved to the square when the playback speakers were without power, and to repair.D8nservice manual download site
Connect to a speaker on the back of the power switch, measuring AC220V DC resistance of the plug between your feet, and to determine whether the power transformer primary circuit breaker, circuit breakers and insurance, the measured resistance is infinite. After opening speaker cover, found that toroidal power transformers have been falling due to mounting bolts loose. The transformer primary and secondary aluminium wire around the system,D8nservice manual download site
D8nservice manual download site
Just switch on the bottom edges of the transformer section, primary winding wire is cut off. After rewound transformer power, was silent for a long time. For ease of maintenance, plotting the relevant circuit, as shown in Figure 1.D8nservice manual download site
D8nservice manual download site
The power amplifier inputs with noise muting control circuits. Connect AC220V power source, rectifier circuit output voltage of 30V power supply, amplifier level enters normal working state. Meanwhile, the +30V voltage via R2 D2 positive, because D2 V2 b-e junction in a circuit in a State of positive series,D8nservice manual download site
D8nservice manual download site
Thus, V2 b-e junction are partial saturation of conduction, V2 collector the equivalent of grounding, sending the signal from the preamplifier bypass and amplifier is muted, does not produce impact noise in the speakers. In addition, the +30V voltage to charge through R1, C1, with the charging time increases, C1 voltage slowly rise, when more than DW voltage value (5.6V), the DW breakdown, V1 for bias voltage and saturated hydraulic conductivity, and DZ cathode voltages down to nearly 0V,D2 due, V2 by disarmament, squelch, power amplifier input-side access to the audio signal.D8nservice manual download site
C1 has a charge-discharge phenomena measured by on the road, and R1 's resistance on the road has been much greater than the 47k, which is a clear exception. Substitution with a 68kSl resistor R1 after commissioning, troubleshooting.

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