Brand:
LG
Category: Desktop Computer
Document Type: Manual
Language: EN
Manual for L1918S
Uploaded: Nov. 21, 2025, 7:03 p.m.
Manual Publish Date: 2007-01-01
This manual provides detailed information on the operation, troubleshooting, and servicing of the LG L1918S monitor. It covers specifications, disassembly, block diagrams, and repair procedures for various components. Key sections include safety precautions, schematics, and parts lists to guide technicians through maintenance and repair tasks.
Troubleshooting and error codes
| Problem | Possible Cause | Solution |
|---|---|---|
| 1. NO POWER (Power Indicator Off) | AC power cord not properly inserted or AC line unstable. | Reinsert AC cord and ensure AC line is normal (100-240V). |
| Faulty adapter/inverter section. | Check the adapter/inverter section. | |
| Q702 or U701 faulty. | Measure Q702 (Vout=1.8V, U701 PIN2=3.3V). If incorrect, check CN701 or replace Q702, U701. | |
| X401 oscillation waveforms abnormal. | Check X401 oscillation waveforms. If abnormal, replace X401. | |
| U401 faulty. | Replace U401. | |
| 2. NO RASTER (OSD Is Not Displayed) - LIPS | Power board issues or short circuit on power lines. | Check power board for short points. |
| U701 output voltages incorrect. | Check U701 PIN 3 (5V) and PIN 1 (3.3V). If incorrect, check U701. If correct, check C712, 714. | |
| D701 voltage incorrect. | Check D701 (1.8V). If incorrect, check Q702, D701, D702, or the scaler IC. | |
| CN701 PIN1 voltage incorrect. | Check CN701 PIN1 (5V). If incorrect, check the BL ON/OFF pulse with an oscilloscope. | |
| LIPS board issue. | Proceed to LIPS troubleshooting. | |
| 2. NO RASTER (OSD Is Not Displayed) - MSTAR | SCALER PIN96/97 not oscillating at 14.318MHz. | Check C421, C423, X401, or the scaler IC. |
| SCALER IC PIN27/PIN28 sync signals incorrect. | Check connection from D-SUB to scaler. | |
| Trouble in cable or LCD module. | Replace cable or LCD module. | |
| 4. TROUBLE IN DPM | SCALER IC PIN27/PIN28 sync signals incorrect. | Check H/V sync line. |
| Trouble in cable or LCD module. | Replace cable or LCD module. | |
| 5. POWER | AC line voltage incorrect or unstable. | Check AC line voltage (110V or 220V). |
| Voltage at C905 incorrect. | Check voltage at C905(+). If incorrect, check F901, BD901. | |
| Start voltage for IC901 PIN3 incorrect. | Check start voltage for PIN3 of IC901. If incorrect, check R906, R907, IC901. | |
| Auxiliary voltage (IC901 PIN 7) not within range. | Check auxiliary voltage (10V-16V jumping). If incorrect, check D902, D902, C907. | |
| Component failure. | Check IC901, T901, Q903, ZD903, ZD904, IC902, IC903. | |
| 6. RASTER | C811 voltage incorrect. | Check C811(+) =12V. If incorrect, check power section. |
| ON/OFF signal incorrect. | Check ON/OFF signal. If incorrect, check interface section or main board. | |
| IC801 PIN 2 voltage incorrect. | Check IC801 PIN 2 =5V. If incorrect, check Q801, Q802, Q803, ZD801. | |
| IC801 output sawtooth wave abnormal. | Check IC801 PIN 5/PIN6. If abnormal, replace IC801. | |
| Q805/Q806 PIN 5/PIN8 voltage incorrect. | Check Q805/Q806 PIN 5/PIN8 is 12V. If incorrect, cut all pin connectors of Q805/Q806, check C811 (+)=12V, and check Q801, Q802. If still incorrect, replace Q805/Q806. | |
| PT801/PT802 PIN 7/PIN8 voltage incorrect. | Check PT801/PT802 PIN 7/PIN8 = 650V. If incorrect, replace PT801/PT802. | |
| Backlight failure. | Replace backlight. |