Trouble Diagnosis And Repairing Method For Representative Symptoms - Daewoo DT-4220NH Service Manual

TROUBLE DIAGNOSIS
(2) Symptoms of MAIN or SUB PCB Trouble
<Symptom.1> Only a weak discharge shows on the screen, but it is displaying No images.
<Symptom.2> Images are abnormal
<Symptom.3> Particular input signal (Video, PC or Component etc.) does not work.
<Symptom.4> No SOUND
<Symptom.5> Occasionally, set does not operate normally. Turning off and on the AC power make
the set to operate normal again.
<Symptom.6> Remote Control or KEY does not work.
<Symptom.7> POWER SHUT DOWN occur (refer to Service Manual I. 9-3 )
(3) Representative Symptoms caused by bad Connection between PCBs.
[Note] Dust or extraneous materials may cause bad connections. Most of the time, applying soft
brush, AIR FRESHER, or breath to clean dust or extraneous materials can solve it. And
then reassemble the Connector.

9-3. Trouble Diagnosis and Repairing Method for Representative Symptoms

(1) When POWER SHUT DOWN occurs
<1> Definition of "SHUT DOWN"
- While LED color is green, POWER PCB does not make any operating noise. (Red: STAND
BY, Green: Operating)
- When the set is turned on power relay does not operate normally, and POWER PCB does not
make any operating noise.
<2> Trouble Repairing Procedure
- As shown in Fig. 5, first check whether "LOW VOLTAGE" part or "HIGH VOLTAGE" part has
problems.
- If "LOW VOLTAGE" part's problem is detected, diagnose and repair the SET as shown in Fig. 6.
- If "HIGH VOLTAGE" part's problem is detected, diagnose and repair the SET as shown in Fig. 6.
- <Caution1> When disconnecting/connecting connectors, you MUST turn "OFF" the AC power
- <Caution2> Whenever you reassemble connectors connecting High Voltage Board and
and check the direction and position of the connectors before working.
POWER PCB(CN805, CN806), remaining voltage still exists in the POWER PCB
could cause electric shock and damage the set. Therefore always reassemble the
connectors several minutes after AC power is off. To be more careful, using a
MULTIMETER you should check to see if Vsus is less than 10V and then connect
connectors.
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