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SD-CX1W
TO CHECK AND CANCEL PROTECT CIRCUIT DETECTION LINE
1. After power supply, the microcomputer (ICD01) built in this
model consecutively monitors the following errors 1 to 4. If
any error occurs, 'Er_AP00' is displayed and all power
supply except for the one to drive the microcomputer is
interrupted.
1. Abnormal output voltage drop of each regulator.
(below approx. 3 V)
2. Excessive output offset of 1-bit amplifier.
(over approx. 2 V of DC potential)
3. Excessive main supply current of 1-bit amplifier.
(over DC approx. 5 A)
4. Abnormalities of cooling fan motor and its driving circuit.
(stop, etc.)
2. Criteria for judging errors of built-in microcomputer and
checking/cancelling detection line.
Condition: The voltage of microcomputer pin 7 (PROTECT)
lowering below 3.5 V is regarded as an error.
(In the demonstration mode to stop cooling fan, the voltage
of 1.5 V is regarded as an error.)
Checking/Cancelling
Caution: When interrupting the PROTECT detection line,
the microcomputer does not operate protectively.
In case of an error caused by output short-circuit of
each regulator, components and board on the spot
may be burnt. Do not interrupt the PROTECT
detection line of the microcomputer, if any cause
other than the above mentioned is not identified.
(For approx. 0.5 seconds after error detection,
power is supplied; power supply can be checked
with an oscilloscope, etc. As leading and trailing
edges of the voltage are so steep that the power
supply cannot be checked by the tester.)
1. Abnormal output voltage drop of each regulator
Connect the measuring apparatus (oscilloscope, etc.) to
the stabilized output of the regulator to turn on the unit
power switch.
If the stabilized output is far smaller (below approx. 3 V)
than that shown in the circuit diagram, the regulator and
the circuit to be supplied with the power may be defective.
2. Excessive output offset of 1-bit amplifier
After disconnecting the CNPV99 (speaker output
connector of 1-bit amplifier), turn on the unit power for the
normal operation. (No sound is heard from the speaker.)
* After repairing, adjust the output offset voltage of 1-bit
amplifier as shown on page 22.
If the protective operation is observed even after
disconnecting the CNPV99, circuits QV95 to 98 (DC
voltage detection of speaker output) may be defective.
3. Excessive main supply current of 1-bit amplifier
After disconnecting the CNP801 (main power source
connector of 1-bit amplifier), turn on the unit power for the
normal operation. (No sound is heard from the speaker.)
* After repairing, adjust the output offset voltage of 1-bit
amplifier as shown in page 22.
If the protective operation is observed even after
disconnecting the CNP801, the circuit of ICV98/ICV99
(supply current detection circuit) may be defective.
4. Abnormalities of cooling fan motor and its driving
circuit (stop, etc.)
Turn on the unit to visually inspect the cooling fan motor
till the protective operation starts.
* If the fan is rotating forcefully.
QV94, contact of the CNPV97 (connector for fan motor),
or fan may be defective. (CNPV97 pin 3 potential during
normal fan operation is approx. 0 V.)
* When the fan is not rotating or seems to be stopping.
If it is checked that the CNPV97 (connector for fan
motor) is not defective and it is also checked by
oscilloscope, etc that voltage of pin 1 (red line of fan) is
approx. 5 V, the fan may be defective.
When the voltage of the CNPV97 pin (1) is far lower
than 5 V, and base voltage of QV93 is almost the same
as that shown in the circuit diagram, the fan or the
circuit consisting of PS801, QV91, QV87, and QV93
may be defective.
When the base voltage of QV93 is 0 V or extremely
lower than the value shown in the circuit diagram (3.5
V), (FAN-L) and an illustrated line (connector) contact
defect or the defect of ICD02 (pin 9) is doubtful.
– 16 –
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