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Protection circuit that activates against a POW ERR error
2 When the main power supply becomes LO level because of short-circuit or disconnection of connectors
2 -1 Short-circuit-detection circuit for the amplifier power circuit (+15 V[VP+15], VD+5, -12 V [VA-12]) Circuit for shutting the power off when VP+15, VD+5, or VA-12 is short-circuited to ground (GND) 2 -3 Checking for VA+12 or VM+12 is short to Gnd or Not.
A
� In Normal mode, as Q101 (Q103) (E2, B2, C2) and Q102 (Q104) (E2, B2, C2) are on, the voltage at Point A is about 5 V. The voltage at Point B is therefore about the same. As Q101 (Q103) (E, C, B) is off, Q102 (Q104) (E, C, B) is also off. (1) When VH+(VP+15) is short-circuited to GND As the voltage at Point B becomes almost ground potential, and Q101 (Q103) (E, C, B) then Q102 (Q104) (E, C, B) are turned on, the level of XPROTECT becomes low. � The microcomputer detects the XPROTECT level and shuts the power to the unit off. (2) When VH-(VA-12) is short-circuited As the electric potential of VE at Q102 (Q104) (E2, C2, B2) becomes the same as that at VB, Q102 (Q104) (E2, C2, B2) is turned off. Following this, Q101 (Q103) (E2, B2, C2) is turned off, which changes the voltage at Points A and B to a value other than 5 V. Therefore, Q101 (Q103) (E, C, B) then Q102 (Q104) (E, C, B) are turned on, the level of XPROTECT becomes low. (3) When VD+5 is short-circuited The level of the XPROTECT line becomes low. The microcomputer detects the XPROTECT level and shuts the power to the unit off. 2 -2 Short-circuit-detection circuit for the DVD power supply (VP+8)
If VFDP is short-circuited to GND, or if the DC electric potential at FL AC1 becomes GND level (in Normal mode: about -27 V) because of a failure in the DC bias circuit of FL AC1, Q107 then Q115 are turned on, and the level of XPROTECT becomes low. � The microcomputer detects the XPROTECT level and shuts the power to the unit off.
C
3 When the FAN connector is disconnected or when rotation of the fan is interrupted
If no fan is connected between FAN+ and FAN-, or when the fan cannot rotate because of a foreign object caught in the blades, the BASE of Q3652 becomes OPEN, and Q3652 and Q3651 (E, C,
E
XPROTECT
Q106 DTC124EUA Q107 DTA124EUA TUNER
B) are turned off. Then Q3651 (E2, B2, C2) is turned on, and the level of XPROTECT becomes low. � The microcomputer detects the XPROTECT level and shuts the power to the unit off. When FAN+ and FAN- are short-circuited, the electric potential at Point A becomes higher than GND level by the addition of the values at D3656 and D3657. As this value is lower than that at D3658, Q3651 (E, C, B) is turned off, Q3651 (E2, B2, C2) is turned on, and the level of XPROTECT becomes low.
F
As the TUNER line is fixed to GND level, Q107 is always on. If the level at VP+8 falls to GND level because of short-circuit, etc., Q106 is turned on, and the level of the XPROTECT line becomes low. � The microcomputer detects the XPROTECT level and shuts the power to the unit off.
