Power Failure Circuit - Sanyo DP26648 Service Manual

CPU (IC800) is programmed so the set will go to standby
mode when there is circuit failure as described below.
(Refer to"Block Diagram Power Lines".)
This unit is equipped with a Power Failure Detector function
included in the CPU which checks for an abnormal condi-
tion in the chassis power supplies.
If, while the power is on, a failure is caused by any of the
following that results in a low voltage supply, the CPU will
turn the unit off in 1.5 seconds to prevent further damage:
•
Failure within the power supply circuits.
•
A short circuit in the load side from the supply.
Power Failure: Detected voltage failure for circuit.
(Connected to IC800 pin 32 and pin 23.)
(Normal: High; Failure: Low)
If, while the power is off, the power is switched on and any
of these failures remains uncorrected, the CPU will shut off
the power within three seconds.
Inverter
Power Board

POWER FAILURE CIRCUIT

IC800 (CPU)
K8B
1 Power On
18
IC1680
5V
LVDS
Check the following if the unit is turned off by the power
failure detector.
1. Disconnect the AC power cord (120V AC line) for a short
time.
2. Connect a DC Voltmeter to the circuits shown below.
3. Press the Power key and check for the proper voltage
supplies.
4. If any of these voltages is low, the power failure detec-
tor should turn the unit off within three seconds.
5. Check all circuits shown below.
Note: If power failure is detected 3 times in 15 minutes,
the set will enter the standby mode and cannot be
switched On.To reset the operating programs of the
CPU it is necessary to disconnect the AC cord for a
short time.
Main
Power Fail
Q810/Q811
32
Power Fail
23
(LVDS)
D1683
2
— 5 —
D1621
D1620
5 Q1610
3.3V
6
D1653
8
IC1651
6.5V
D6053
D6052
6 IC6050
3.3V
D1671
5
IC1671
9V
D1662
6
IC1661
5V
D1679
IC001
9
10V