Text preview for : 04. Troubleshooting .pdf part of Samsung syncmaster 920NW By Prem
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4 Troubleshooting
4 Troubleshooting
4-1 Common Acknowledge
- If you change the interface board, be sure that the U105, U106 and U103 these three components also changed to the new I/F board because there was program inside. If not, please re-write EDID or upload firmware into Flash memory via VGA Cable. - If you adjust clock and phase, please do it at the condition of Windows shut down pattern. - If you confirm the R.G.B. color is normal or not, please do it under 16-grey scalar pattern. - This LCM is analog interface. So if the entire screen is an abnormal color that means the problem happen in the analog circuit part, if only some scale appears abnormal color that stand the problem happen in the digital circuit part. - If you check the H/V position, please use the crosshatch pattern. - This LCM support more than 30 timing modes, if the input timing mode is out of specification, the picture may appears abnormally. - If brightness uneven, repairs Inverter circuit or change a new panel. - If you find the vertical line or horizontal line lost on the screen, please change panel.
4-1
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4 Troubleshooting
4-2 No Power & Power LED Off
No power
Check primary rectifier voltage
Check circuit if short
Check IC802, C805, T801
Check F801, P801, RT,801,D801 Check pin6 of IC802 voltage about 12V
Check C810,D803,C807
Check pin2 of IC802 voltage about 3V
Check primary OVP, OLP and secondary feedback,
Check pin1 of IC802 voltage is voltage is below 1V
Check R811, R810, R809, R808,R814
END
4-2
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4 Troubleshooting
4-3 Output power is unstable
Unstable power
Check sampling Circuit
Check R822, R823, R824
Change R822, R823, R824 Check the R pin voltage of IC803 about 2.5V Check the C pin voltage of IC803 if 3V
Change IC803
Check R819, R820
Check pin1 of IC802 voltage is 5.8V
Check R818, D804, C807 if short
Change R818
Check pin1 of IC802 voltage about 3V
Change R808, R809, R810, R811
END
4-3
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4 Troubleshooting
4-4 Backlight can't be turned on
No backlight Yes No LED lamp is OK Yes
No power supply to inverter
Check the cable that from I/F BD to P/I BD is ok
Yes Is there 14V voltage on pin 3,4 of T501, T502 Yes Is there PWM signal on pin 4 of IC501 Yes Is there High level voltage on pin10 of IC501 Yes No Lamp connector opened No Check I/F BD No Check I/F BD No U501, U502 fail No Check power supply
Replace U501, U502
Vsense voltage 2.9V No Are there PWM signal on pin1, pin15 of IC501 Yes Pin 5 of IC501 voltage is Low level Yes Pin 3 of IC501 voltage is high level voltage
No IC501 failure
Yes Feedback circuit failure
Yes
Check C524,R528, R533, D507
Yes IC501 protected
Yes
Check D505, D511, D512, R513, R520, C520
END
4-4
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4 Troubleshooting
4-5 Black Screen and backlight turn on
Black Screen
Check power supply: Pin1, 2 of CN102 Yes Check pin34, 51, 66, and 82 Of U105 Yes Check pin12, 68, 97 and 117 Of U103 Yes
No Power Fail
No Check FB103 And U102
No Check FB105 And U106
Check Reset (pin19) Of U103 Yes Check Crystal: Pin32, Pin33 Of U103 Yes Check CCFLEnable (pin20) of U103 No MCU Fail Yes
No Check C149, R157
No Check: X1, C147, C148
Check pin5 of CN102 No
Yes Inverter Fail
Check R127, Q101, R125, R126
4-5
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4 Troubleshooting
4-6 White Screen
White Screen
LVDS Cable Reinsert No
Yes Workmanship
Change LVDS Cable No Yes
Yes LVDS Cable NG
Check VLCD Is 5V? No Check Panel Enable Of U103 (pin75) is High?
Check LVDS Signals No Check the HW Reset Of U103 pin19 No Yes
Yes Panel Fail
No Check C149 R157
Check R134, R176, Q102, Q105 Check the pins Of U103
END
4-6
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4 Troubleshooting
4-8 Bad Screen
Bad Screen
LVDS Cable Reinsert No
Yes Workmanship
Change LVDS Cable No Check Crystal:Pin32, Pin33 of U103 Yes Check the communication Of U103 and U104 Yes Check the pins of U103 and U104
Yes LVDS Cable NG
Yes Check :X1, C147, C148
No
Check: SDO, SCZ, SCK, SDI, Reset
4-7
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4 Troubleshooting
Memo
4-8