Troubleshooting Guide - LG Flatron L1751S-SN Service Manual

NO POWER
(POWER INDICATOR OFF)
CHECK J705 VOLTAGE
1
PIN5, PIN6 (5V)?
CHECK
U801 PIN 1& U803 PIN
1
3 VOLTAGE
(5V) ?
CHECK
Q803 PIN 3(3.3V) & U803
PIN 4 (1.8V)?
CHECK KEY CONTROL
CONNECTOR ROUTINE
IS U201
PIN88
2
VOLTAGE REPEATED
AS PULSE
SHAPE ?
CHECK IIC LINECONNECTION
(U501, U502)
Waveforms
1
J705-#5, 6 / U801-#1/U803-#3

TROUBLESHOOTING GUIDE

1. NO POWER
YES
YES
YES
YES
2
U201-#88
NO
NO
NO
NO
CHECK U201 VCC, XTAL,
RESET
- 14 -
CHECK POWER BOARD,
AND FIND OUT A SHORT
POINT AS OPENING
EACH POWER LINE
CHECK U801.
CHECK 5VR LINE
(OPEN CHECK)
NO PROBLEM