Dvd Center Unit (Htz-C7); Powered Subwoofer (Htz-Sw7); Diagnosis; Fail-Safe - Pioneer HTZ-7 VisionPlus Service Manual
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HTZ-7, HTZ-C7, HTZ-SW7
7.2 DIAGNOSIS
7.2.1 FAIL-SAFE
DVD Center Unit (HTZ-C7)
1. System Reset after Detection
Check of the power supply line (3.3 V line)
(AD3: Pin 32)
Fail-safe for prevention of crashing of the DVD microcomputer
(system controller) with occurrence of power supply ripples. (ADC
read value for the power supply voltage of the player section at the
time of power ON)
System reset is applied when the threshold value is not reached six
times in a row during power ON.
Operation explanation
The power supplied to the DVD assembly is composed of the three
types +12 V, +5 V, and +3.3 V, and of these, the 3.3 V system is
detected at all times.
In the following diagram, dropping of the +3.3 V system to 3 V or
less because of power supply trouble is detected, and the power
supply is switched off.
Trouble (sag etc.) occurrence
3.3V
0.3V
Power OFF and
rapid drop
Power ON
Power OFF
3.3 V system Trouble Detection
Check of the power supply line (5 V line)
(AD6: Pin 35)
Fail-safe at the time of disconnection from the power outlet. As the
power for the AV controller is supplied from the powered subwoofer
section, this kind of fail-safe becomes necessary. A system reset is
applied when the ADC read value for the power supply voltage of
the DVD center unit twice in a row drops below the threshold value.
Cooling fan trouble detection (AD2: Pin 31)
When the cooling fan stops to run because of a defect, entry of
foreign matter, etc. and energization is continued, there is the
possibility of burning, so that a circuit for detection of this condition
is included. A system reset is applied when the ADC read value for
the cooling fan operation detection port twice in a row drops below
the threshold value.
Operation explanation
When the fan is operating in the fan detection circuit, a current
flows, so that a potential difference occurs at R5056 and Q5515
becomes ON. In this case, the anode potential of D5509 is –
(minus), so that the potential becomes a reverse maximum voltage
and D5509 does not open. Accordingly, Q5512 is OFF and pin 3
of the microcomputer reaches high level. When the fan rotation
stops, Q5513 becomes OFF and the potential at C becomes +. Then
D5509 becomes ON, and as the result, Q5512 becomes ON.
Then pin § of the microcomputer becomes low level.
The microcomputer at all times monitors pin §, and when this
becomes low level, forced entry into standby mode is performed
and the power supply of the set is switched off.
+5V
+12V (M)
R5575
R5584
31
D5509
FAN
Q5513
IC5501
R5586
Q5512
µ-com
R5587
R5056
R5585
R5053
–12V (M)
Fan Detection Circuit
Communication error with the DVD system controller
A system reset is applied when serial communication with the DVD
system controller fails 32 times in a row.
2. Stop Mode after Detection
(The appearance is a simple system reset.)
Check of the AV control power supply line (5.6 [V]
line) from the powered subwoofer unit (AD1: Pin 30)
When the power supply for the AV controller drops off, the AV
controller enters stop mode and memory backup is performed.
When the ADC read value for the power supply voltage twice in a
row drops below the threshold value, stop mode (power saving
mode) is entered and the memory contents are backed up.
Powered subwoofer (HTZ-SW7)
1. Power OFF after Detection
DVD center display communication interruption
Power OFF is performed when the REQ edge of the DVD center
display communication is interrupted for 1.5 sec. (The count value
of the internal 1 ms timer is used for the judgment.)
Overcurrent detection
Power OFF is performed when the overcurrent detection port
(always “H” while the power is ON) becomes “L”. (Judgment is
performed once with the main loop.)
Abnormal temperature detection
An abnormal temperature is judged to exist when one of the
abnormal temperature detection ports (A/D input, 2 ports) becomes
4.3 V or higher, and then the power is switched off. (Judgment is
performed once with the main loop.)
Overvoltage detection
An overvoltage is judged to exist when the overvoltage detection
port (A/D input port) drops to 3.5 V or less, and then the power is
switched off. (Judgment is performed once with the main loop.)
2. System Reset after Detection
Abnormal AC pulse
When the AC pulses have been interrupted for 2 pulses, reset start
is performed. (Judgment is performed once with the main loop.)
Page 106
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