Daewoo DT-4220NH Service Manual download pdf (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

<Symptom.1> Not even a weak discharge detected on the screen.

<Symptom.2> Discharge on the screen is unstable

<Symptom.3> Set is making unusual noise

<Symptom.4> POWER SHUT DOWN occur (refer to Service Manual I. 9-3)

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Daewoo DT-4220NH Service Manual Page 48