Daewoo DPN-4274NHS Service Manual - page 48
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9. TROUBLE DIAGNOSIS
[NOTE] Refer to “PDP MODULE” section for module diagnosis.
* Refer to Chapter II for Symptoms of other parts with exception of MAIN, SUB PCB and POWER
PCB Trouble.
9-1. Facts you must know when trouble diagnosing or repairing
(1) Trouble diagnosing and repairing of set mean find out which PCBs or blocks are not working and
replace them with new PCBs. Repairing the broken PCBs are not necessary. Keep the broken
PCBs and return them to service center or R&D center.
(2) This TROUBLE DIAGNOSIS list only contains representative and simple PCB trouble diagnosis
and Module Exchange method. Therefore, if you find Sets that are difficult to diagnose or to
repair, contact R&D center.
(3) Basic TROUBLE DIAGNOSIS procedure
Check problem Symptoms -> Open BACK COVER -> Trouble Diagnosis e Replace broken PCB
-> Adjust new PCB module -> HEATRUN (for at least 30 minutes, input TEST PATTERN FULL
WHITE), full FUNCTION test -> Repair Complete.
(4) Required equipments for trouble diagnosis
- DIGITAL MULTIMETER (User Mode : measure DC VOLTAGE, measure DIODE VOLTAGE,
SHORT-OPEN TEST )
- Screwdriver (or electric screwdriver), plastic adjusting tool
- Oscilloscope (for detailed examination only)
(5) Each BLOCK operations explained in this manual include OSCILLOSCOPE waveforms, but these
are for reference only and utilizing them to repair PCBs is not necessary.
(6) Before replacing PCBs, you MUST turn the AC Switch “OFF”.
(7) After replacing High Voltage Board, POWER, and MAIN & SUB PCB, extra adjustment might be
needed. (Refer to I. 6. Adjusting Method)
(8) After the set is repaired, leave BACK COVER open for followings. Run HEATRUN for at least
30 minutes by displaying TEST PATTERN (FULL WHITE) of SERVICE MODE (Refer to
Service Manual I.5. Service Mode). Check the screen conditions and basic functions (remote
control operation etc.).
(9) After BACK COVER is closed, redo HEATRUN for at least one hour with FULL WHITE input
using TEST PATTERN of SERVICE MODE. Check the screen conditions and basic functions.
9-2. Typical Symptoms of PCB problem or bad Connection
(1) Symptoms of POWER PCB Trouble