Analysis of maintenance: under normal circumstances, connected AC220V power supply red led is blinking, loudspeaker protection delay ended after about two seconds, the relay sucks and lights stay lit. If the speaker protection circuit, the relay disconnects, blinking lights, tip the machine is faulty.kDNservice manual download site
kDNservice manual download site
Symptoms from this computer, the speaker protection circuit has been started, for ease of maintenance-mapping out the parts of the circuit, as shown in Figure 1.kDNservice manual download site
kDNservice manual download site
The protection circuit uses the classic double triode, RC delay structure. Power up the transformer secondary output AC voltage by 2 type 1N4007 diode full-wave rectifier, 2 150 ω/2W resistance pressure restrictors, after a 100 μl F/35V capacitor, 15V Zener diode 15V voltage clamp. The voltage via the R6 on the C4 charge, C4 voltage slowly rise, when up to a certain value, the partial pressure of R7, R8 V4, V5 full-in-conduction, relays, contact snap,kDNservice manual download site
kDNservice manual download site
Play the role of delay through the speakers. If left channel or right channel output midpoint voltage disorders, midpoint voltage for must value of are voltage or negative voltage, is by V1, and V2 detection Hou, its set electrode voltage close 0V, equivalent V3 base very grounding, V3 saturated guide pass, its launches very voltage close 0V, and C4 was short-circuit, is V4, and V5 due to lost partial reset voltage and as, V5 set electrode voltage liters to 14.8V around, following electrical lost electric, touch points disconnect, to achieved on speakers of protection.kDNservice manual download site
Power output tube had flow protection: Dang power output tube V10 (right channel power output level pushed pull Shang tube, set electrode received VCC +47V) or V11 (left channel power output level pushed pull Shang tube, set electrode received VCC+47V) of launches very current had big Shi, in R9 Shang produced of voltage drop also will synchronization variable big, this detection voltage through R11, and R4 plus in V8 (C945) of knot Shang, is V8 guide pass, through D6 put V3 base very voltage pulled low, V3 full collection guide pass, C4 was short-circuit, V4, V5 cut-off due to lose bias,

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