VP+8 is Power Line when the set is DVD Function (TUNER is High level). At this time when VP+8 is short-circuited, as TUNER is Low level, Q106 turns ON and XPROTECT becomes Low level. �U-com detects the XPROTECT level and sets Power OFF. Except DVD Function even if VP+8 is GND level, as TUNER is also High level, Q107 is OFF and XPROTECT does not become LOW level.
AMP Assy
R3656 22k
D3656 S5688G Q3654 2SD2144S (VW) V-12F
B
When the FAN is not connected between FAN+ and FAN-, or FAN is locked state as the foreign matter is blocked, Q3652 Base turns open, and then Q3652 and Q3651(E, C, B) turns OFF. Then Q3651 (E2, B2, C2) turns ON and XPROTECT becomes LOW level. �U-com detects the XPROTECT level and sets Power OFF. When FAN+ and FAN- is short-circuited, A point voltage becomes higher than GND level because of part D3656 and D3657. Then it is lower than part D3658, Q3651(E, C, B) turns OFF and Q3651(E2, B2, C2) turns ON, and XPROTECT becomes LOW level.
5 DC Detection Circuit of SP Terminal
POWER Assy
R3605 (R3625,R3615) 27k FL (SW, SL) FR (C, SR) R3638 10k C3632 470/6.3 R3606 (R3626,R3616) Q3637 27k B Q3638 C XPROTECT +5V Q3632 E
AMP Assy
VD+5 R108 27k
7 Short Circuit Detection Circuit of VFDP
AMP Assy
VD+5 R108 27k
¶ At normal state both Q3637 and Q3638 are OFF. (1) When (+) side DC Voltage occurs at SP terminal When (+) side DC voltage occurs at L ch or R ch and VB of Q3637 becomes higher than operating point, Q3632(E, C, B) turns ON and XPROTECT becomes Low level. � U-com detects the XPROTECT level and sets Power OFF. (2) When (�) side DC Voltage occurs at SP terminal It is reverse operation as (+) side. Q3638 turns ON and XPROTECT operates.
R112 1k
R113 220k
When VFDP is short-circuited to GND or DC voltage of FLAC1 becomes GND level because of DC bias failure of FLAC1 (normal state voltage is �27V), Q107 turns ON and also Q115 turns ON, then XPROTECT becomes LOW level. �U-com detects the XPROTECT level and sets Power OFF.
D
[How to return from the protection circuit operating]
XV-DV303 operates the protection circuit under the following conditions and makes the set Power OFF. 1. When major voltage becomes down to low level because of short-circuit or without connection. 2. When detecting abnormal thermal rise by the thermistor. 3. When being disconnected Fan connector or blocked of the Fan rotation 4. When making the Speaker connector short-circuited. At this time the timer LED of the front panel blinks and informs the abnormal state. When operating the protection circuit, if it works by above condition 4, it is possible to return immediately by the Power ON button. If it operates by other conditions as above condition 1 to 3, it is possible to return by turning the Power ON 1 minute after starting protection circuit operation. When it is necessary to turn the Power ON without waiting 1 minute, pull out the AC plug and discharge the both terminal of the backup capacitor (C5575) of U-com board. By doing so, as the U-com is reset to the initial state, it is possible to set the Power ON again immediately.
E
