LG 26LH1DC1-UB Service Manual page 23

1. Check if the SMPS power is connected to the Main board and stand-by power connected, and whether green light is on for LED(D101).
If the green light is not on, check the stand-by power(5V).
2. Turn ON the POWER using the remote controller or the front key button.
At this time, check whether the green light is on for LED (D102).
If the green light is not on, measure the next power with DMM.
- Pin no. 3, 4 and 5 of CN101 (D12V)
- Input/output voltage of IC503 (D12V, D6V)
- Input/output voltage of IC710 (D6V, A5V)
3. Check whether the LCD panel is operating normally.
If the display is not working normally, check the LVDS cable and take the following actions.
- Check the input/output voltage of IC501. (D12V, D3.3V)
- Check the input/output voltage of IC704. (D3.3V, D2.5V)
- Check the input/output voltage of IC714. (D3.3V, D1.8V)
- Connect the UART Cable to the Service Port and activate the debugger window of the PC.
After connecting the power to the Main board, check whether the booting flow is normally written in the debugger window of the PC.
(To enable communications with the PC, always use the UART cable checked for normal operation.)
- If the booting flow is not written at all in the debugger window of the PC, check the power(D3.3V, D2.5V, D1.8V) connected to the main chip(IC401).
And then if there is no problem with the power, check the connection pattern condition of the main chip(IC401) and the Flash memory(IC403),
and check the cold solder or short circuit of each pin of the flash memory.
- If only 1 line of booting flow is written in the debugger window of the PC and nothing after that, check the power(D3.3V, D2.5V, D1.8V) connected
to the main chip(IC401).
And if there is no problem with the power, check the cold solder or short circuit of the array resistance(RA403-RA416) connected to the main chip
and DDR memory(IC402 and IC404).
Check the cold solder or short circuit of each pin of the DDR memory.
- When the booting flow is normally written in the debugger window of the PC but rebooting, check the communications line(SCL1, SDA1) of MICOM
(IC705) and main chip(IC401).
4. Check whether the digital broadcasting is normally received. If it is not normally received, check the following.
- Measure the power of no. 3 pin of TUNER(IC105). (TU5V)
- Measure the power of no. 12 pin of TUNER(IC105). (TU3.3V)
- Measure the power of no. 15 pin of TUNER(IC105). (TU1.8V)
- Check the cold solder and short circuit etc. of the serial resistance(RA101, RA102) and other resistances(R114~R116) of the TS Data line.
- Check the communications line(SCL0, SDA0).
5. If the digital broadcasting is normally received but the analog broadcasting is not received normally, check the no.16 pin of IC706(74VHC4051).
(CVB_5V) For a more detail review, check the signal wave form of Q106, Q101, Q104 etc. with the oscilloscope.
6. Check if the external input of AV1, 2, 3, S-Video etc. If the video does not show well, check whether there is any problem with IC706, which is the analog
video switch.
If a specific external input does not work, check the external input device and check whether there is any problem with the cable.
If not identified simply, check for problems following the signal of "Video/audio signal flow chart".
7. Check the external input of Component1 and 2.
If the video of the Component does not work at all, check if there is any problem in IC202, the component video switch and IC201, AD converter.
If a specific external input does not work, check the external input device and check whether there is any problem with the cable.
If not identified simply, check for problems following the signal of "Video/audio signal flow chart".
8. Check the PC input and HDMI(DVI) input.
If the PC video does not work, check whether there is any problem with the connection cable.
If the HDMI video does not work or only the video works without any audio, rewrite the EDID data.
9. Check if the left/right side of the audio working normally.
Check the cold solder and short circuit of IC708(STA323W) when the audio does not work.
For analog broadcasting, check the cold solder and short circuit of IC602(MSP3425) since it goes through this.
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Only for training and service purposes
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