LG LH-CX640 Series Service Manual page 61

3-68
2.
SYSTEM
Test
flow
TEST
Check
the AC
Voltage
Power
PCBA(110V or
220V)
Replace
power
PCBA or
AC
transformer.
Switch
on
the
Power
PCBA
Is
the DC Voltage
outputs
OK?
(5V,1.8V,3.3V,8V,12V)
Repair
or
Replace
Power
PCBA
Make
sure
the
main
PCBA
don't
short on VCCs
and
switch
it
on.
Is
3.3V
and
1.8V
DC
outputs
normal
on
main
PCBA?
Check
the
regulators
or
related diodes.
Connect to PC
RS232
Cable
and
update
the
FLASH
memory
code.
Update
FLASH
successfully?
A
1.
Check
27MHz system clock.
2.
Check
system
reset circuit.
3.
Check
FLASH
R/W
enable
signal
PRD,RWR.
4.
Check
RS232
SIGNALS.
5.
Check
FLASH
Memory
related
circuit.
NO
NO
NO
NO
YES
YES
YES
YES