93
1
2
3
4
1
2
3
4
C
D
F
A
B
E
XV-DV303
R108
27k
VP+8
VD+5
XPROTECT
Q106
DTC124EUA
Q107
DTA124EUA
D104
1SS355
XPROTECT
XPROTECT
µ
-com
XPROTECT
µ
-com
FL AC1
Q114
2SD2114K
(VW)
Q3654
2SD2144S
(VW)
Q3652
DTA124TK
Q3651
RN1901
Q3651
RN1901
D3658
UDZS7.5B
D3657
1SS355
FAN+
FAN-
C2
E2
C
E
B
B2
R3605 (R3625,R3615)
27k
R3606 (R3626,R3616)
27k
Q3637
Q3638
E
C
B
Q3633
R3638
10k
R108
27k
Q115
DTA124EUA
D3656
S5688G
D3655
1SS133
FL
(SW, SL)
FR
(C, SR)
V+12F
VD+5
Q3632
+5V
R108
27k
R114
82k
R3656
22k
R3655
8.2k
R108
27k
R3654
1.8k
R3658
2.2k
R3657
33(1/4W)FU
R112
1k
R113
220k
VD+5
VA-12
C3632
470/6.3
C3652
47/50
TUNER
VD+5
AMP Assy
AMP Assy
TRADE2 Assy
AMP Assy
AMP Assy
V-12F
POWER Assy
A
4
Short Circuit Detection Circuit of DVD Power Line
(VP+8)
5
DC Detection Circuit of SP Terminal
6
FAN Detection Circuit
7
Short Circuit Detection Circuit of VFDP
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.
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.
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.
[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 imme-
diately.
¶
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 V
B
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.
