PIONEER XV-DV440
Manual de Servicio

1

2

3

4

A

4 When DC is generated at the output because of a failure in the AMP system, etc.

5 When abnormally high temperature is detected by the thermistor
5 -1 IC81 abnormal temperature detection circuit
VD+5 IC81 NJM7805FA TH111 NCP18WF104J03RB

J
R3605 (R3625) (R3615) 27k Q3637 Front R ch (C, SR) R3606 (R3626) (R3616) 27k +

POWER Assy

D
VD+5

6CH AMP Assy

D

+5V Q3632
E B

6CH AMP Assy
to XPROTECT

R108 27k

Front L ch (SW, SL)

A
XPROTECT
C

R113 220 R112 1k

Q111 2SC4081

R3638 10k

C3632 470/6.3

Q3638

Q3633

R111 1k

B

� In Normal mode, both Q3637 and Q3638 are off. (1) When positive (+) DC voltage is generated at the SP terminal When positive (+) DC voltage is generated at the L or R channel, and VB of Q3637 becomes higher than that at the operation point, Q3632 (E, C, B) is turned on, and the level of XPROTECT becomes low. � The microcomputer detects the XPROTECT level and shuts the power to the unit off.
C

(2) When negative (-) DC voltage was generated at the SP terminal Q3638 is turned on, and XPROTECT is activated.

The voltage at Point A becomes the divided voltage of TH111 and R111//R112 (combined resistance of parallel-connected resistors R111 and R112.) In Normal mode, the resistance at TH111 is much higher than R111//R112, and Q111 is off. (Note that the resistance at TH111 becomes lower as the temperature increases.) If the solder temperature at IC81 increases abnormally, the temperature at TH111 (thermistor) mounted closest to the land of IC81 increases accordingly, and the resistance at TH111 decreases. When the temperature at TH111 reaches 90-110_C (varying according to conditions,) the voltage at Point (A) becomes high enough to turn Q111 on, and the level of the XPROTECT line becomes low. The microcomputer detects the XPROTECT level and shuts the power to the unit off.

D

E

F

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XV-DV740
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