The machines Panel control, output power time setting is normal, that is to set the time after which no voltage amplifier power output socket, and couldn't finish the school bell, playing music during the break.Hp8service manual download site
Hp8service manual download site
Teardown found in addition to display there are two pieces of circuit boards inside the machine: a touch MP3 decoder control circuit board, another is the rectifier voltage relay control circuit board, to facilitate maintenance surveying the road circuit is shown in Figure 1.Hp8service manual download site
Hp8service manual download site
Amplifier power state measuring C1 capacitor voltage at about 13V, IC1 (7805) output voltage 5V normal R1 right voltage 4.8V normal, and R2 voltage is 0V at the top. Use tweezers to short circuit V1 collector and emitter, relay, amplifier power socket has voltage output. Power off Remove optocoupler PC817 found ①, ② feet short and put on new PC817 troubleshooting. PC817 ①, ② short-circuit, ③, ④ feet do not receive optical signals by R2 top voltage cut-off for the 0V,V1 the base voltage is 0V, relays do not snap, so the amplifier power output socket without power.Hp8service manual download site
Hp8service manual download site
Hp8service manual download site
Hp8service manual download site
Editor's Note: Figure 1 relay control coil should be connected in parallel a diode or capacitor, otherwise Vi will be very dangerous, easily penetrated the V1.Hp8service manual download site