Samsung LT20A350 Service Manual page 31

4. Troubleshooting
4-1-2. No Power
- The LEDs on the front panel do not work when connecting the power cord.
Symptom
- The SMPS relay does not work when connecting the power cord.
- The units appears to be dead.
The IP relay or the LEDs on the front panel does not work when connecting the power cord if the cables are
improperly connected or the Main Board or SMPS is not functioning. In this case, check the following:
Major
- Check the internal cable connection status inside the unit.
checkpoints
- Check the fuses of each part.
- Check the output voltage of SMPS.
- Replace the Main Board.
Diagnostics
4-2
SMPS BOARD
Lamp(Backlight) Off,
power indicator LED on?
Yes
Lamp(Backlight) Off,
power indicator LED on ?
Yes
Does proper Stand-By DC A5V
appear at VIA - A5V_PW ?
Yes
Does proper Main DC B13V, B5V
appear at VIA - B13V_PW, B5V_PW ?
Yes
Does proper DC A3.3V
appear at VIA - A3.3V_PW ?
Yes
Does proper B3.3V, B1.5V appear at
VIA - B3.3V_PW, B1.5V_PW
Yes
MAIN BOARD
No
Change the 14p power cable.
No
Change INVERTER/BALANCE B'D.
No
No
Change the Main Assy.
No
No
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