Power Failure Circuit - Sanyo DP50747 Service Manual

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.
1. Power Failure 1: Detected voltage failure for analog
and digital circuits. (Connected to IC801 pin 32.)
2. Power Failure 2: Not used on this model.
(Connected to IC801 pin 36.)
(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.
Sub
Power Board

POWER FAILURE CIRCUIT

IC801 (CPU)
K6D
2 Power On
14
Check the following if the unit is turned off by the power
failure detector.
1. Disconnect the AC power cord (120V AC line) for at least
10 seconds.
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: This unit is equipped with a Power Surge Protection
feature included in the CPU. If power failure occurs
three times within 15 minutes, the CPU will stop func-
tioning automatically to help prevent secondary
damage. (TV will not turn on by pressing the power
key.) To reset the operating programs within the CPU,
disconnect the AC power cord for at least 10 seconds.
Main
Power Fail
Q803
32
Q804
2
Power Fail
36
— 5 —
D1602
D1604
IC1610
2
3.3VD
D1651
9
K8B
12V
D1640
5
IC1640
9V
D1631
2
IC1630
5V
D1621
IC1620
33V