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GD910T-1 Trouble Shooting Flowchart
1. Vertical Oscillator

GD910T-1 Service Manual 1 of 18

Vertical Oscillator Defective

Is The Screen Rolling Vertically?

YES

Check Vertical Sync From U101 #52

NO

OK

Does Vertical Oscillator Waveform Appear at U801 # 24 ?

NO

Check Vertical Circuit of U801

YES

Check Vertical Output IC U601 Circuit

End
1

2. Defective ABL

GD910T-1 Service Manual 2 of 18

Defective ABL

Is the Q409 In Good Condition?

NO

Replace Q409

YES

Is the D414 In Good Condition?

NO

Replace D414

YES

Does DC-45V Appear At VR403?

NO

Replace VR802 or Recheck 45V Source

YES

End

2

3. Picture Brightness Too High/Too Low

GD910T-1 Service Manual 3 of 18

Picture Brightness Too high/Too Low

Raster Too Bright

Raster Too Dark

Adjust Screen VR
FAIL

OK

Adjust Gain (See White Balance Adjustment Process)

Check G1 (-30V)

Check Q413,Q414

Check Video Output Circuits

Check Q411,Q412

Check Spot Killer Circuit Q416,Q415

End
3

4. No Video Raster Only No Picture

GD910T-1 Service Manual 4 of 18

Is The Raster Too Bright ?

YES

Check B+ (78V)

NO

Does DC-78V, 16V And 4.7V Heat Appear At The CRT Board ?
YES

NO

If 16V or 4.7V Heat Fail Then Check Power Source

Does Video Waveform And DC 4.7 to 5V Appear At CRT Socket pin8,pin6,pin10, pin11?
YES

NO

Does Video Waveform Appear At C754,C753,C752
YES

NO

Replace U702

Check Video Input

Check U702 And Related Components

OK

Does DC-0V Appear At U701 # 10 ?
YES

NO

Replace U201,R724

Check U701 # 18, # 26, # 27, # 28

End

4

5. H.V. & Hold Down Abnormal

GD910T-1 Service Manual 5 of 18

H.V. Hold Down Abnormal

Does The HV Drive Waveform Appear At Q408 "Gate"

NO

Check D416/R402/ Q430 and Related Components

YES

Does PWM Sync Waveform Appear At U401 pin 9 ?

NO

Check U401 and Related Components

YES

Does PWM Feed Back Voltage Appear At U402 pin 2 ?

Abnormal

Check ZD419/R433/ R422/R430/C435/ R434/VR401 And Related Components

YES

Check U402 And Related Components

End

5

GD910T-1 Service Manual 6. Horizontal Deflection Defective Horizontal Deflection Defective 6 of 18

Is Picture On The Screen Normal ?

One Vertical Line

Check U801 And Relafed Component

Replace Q801,Q802,Q826,Q8 05,T802,T801

YES

Does The H-Out Waveform Appear At R824 ?

NO

Replace U801,U802,Q801, Q802

YES

Is The H-width Function Normal ?

NO

Replace T803 And Related Components

YES

Is H-width Within Range For Each Mode ?

NO

Replace T803 And Related Component or Re-adjust H-Limit

YES

Is Geometry Adjustment Function Normal ?

NO

Replace U801

End

6

7. H-Hold Unstable

GD910T-1 Service Manual 7 of 18

H-Hold Unstable

Does the H-Sync Waveform Appear At U801 # 15
YES

NO

Re-Initialize Default Value at Logic or Replace U101

Does the H-Oscillator Waveform Appear At U801 # 29
YES

NO

Replace C809, U801 and Relater Component

Is U801 #8 H/O Frequely changed When adjust H-frequency?

NO

Check U801

YES

Does The feed-back H-pules Waveform Appear At U801 #1?

NO

Replace C825,C818

End

7

GD910T-1 Service Manual 8. H-Phase Shift 8 of 18

H-Phase Shift

When Adjusting H-Phase, Is There Waveform At U801 Pin 18,19

NO

Check U101 and Related Components

YES

When Adjusting H-phase, Does The Waveform Shift At U801 #8?
YES

NO

Replace C812,C811,C809 and Related Components

Does The H-Pulse Waveform Appear At U801 #1?

NO

Replace C818,C825

End

8

9. Logic Function Abnormal

GD910T-1 Service Manual 9 of 18

Logic Function Abnormal

Is The I2 C Bus Waveform Normal At U101 # 24, #25 ?

NO

Does DC-5V Appear At U101 # 64 ?
YES

NO

YES

Replace U101,X101 Check U201,U801,U102

Check The Power Supply Circuits

Re-Initialize Default Value At U102

End

9

GD910T-1 Service Manual 10. No Blanking 10 of 18

No Blanking

Is Horizontal or Vertical Retrace Line On Raster ? Replace C825,C818 NO and Related Components Does The H-Pulse Waveform Appear At R715 ? Does The V-BLK Waveform Appear At C623 ? Replace ZD623,D622

NO

YES

Replace Q702 And NO Related Components

Does The H-Pulse Waveform Appear At R718 ?

YES

YES

Replace R704 and NO Related components

Does The H-Pulse Waveform Appear At Q704 "C" ?
YES

Does the V-BLK Waveform Appear At C425 ?

NO

Replace Q622,Q621, D621 And Related Components

Replace U701

End

10

GD910T-1 Service Manual 11. Poor Focus 11 of 18 Poor Focus

Does The CS Waveform Appear At C832 ?

NO

Replace C832

YES

Does The CS Waveform Appear At R302 ?
YES

NO

Replace T301

Does The V-Parabola Waveform Appear At Q301 "B" ?
YES

NO

Check U801 Pin 32 Also Check V-focus default value

Does 350 VDC Appear At R312 ?

NO

Check D406,R303,R310 Related Circuits

YES

Check Q301 And Related Components

End

11

GD910T-1 Service Manual 12. Spot Killer 12 of 18

Spot Killer

Does About DC-400 to 700V Appear At G2 ?
YES

NO

Adjust G2 or Check T401

Is The G1 Voltage Normal ?
YES

Too High

Check Q413,Q414, Q412,Q411 And Related Components

Is The Picture Too Dark or Spot Appeared On the Screen When Power-Off ?
Spot

Too Dark

Replace Q415,Q413

Check D411,D412,Q416 And Related Components

End

12

GD910T-1 Service Manual 13. Rotation Abnormal 13 of 18

Rotation Abnormal

When Adjusting Rotation Function, Is The Voltage Active At R333
YES

NO

Check U101 Pin 18 And Related Components

Does DC Voltage Changed at Q329 Pin E When Adjust Tilt Function

NO

Replace Q329 And Related Components

YES

When Adjust Rotation Function, Is The Voltage Active At B502

NO

Check Q329,R338,Q330 And Related Circuit

YES

Replace CRT

End
13

GD910T-1 Service Manual 14. H-CG Abnormal 14of 18

Rotation Abnormal

When Adjusting H-CG Function, Is The Voltage Active At R329
YES

NO

Check U101 Pin 16 And Related Components

Does DC Voltage Changed at Q326 Pin E When Adjust H-CG Function

NO

Replace Q326 And Related Components

YES

When Adjust H-CG Function, Is The Voltage Active At B301

NO

Check Q326,R331,Q325 And Related Circuit

YES

Replace CRT

End
14

GD910T-1 Service Manual 15. V-CG Abnormal 15 of 18

V-CG Abnormal

When Adjusting V-CG Function, Is The Voltage Active At R323
YES

NO

Check U101 Pin 17 And Related Components

Does DC Voltage Changed at Q321 Pin E When Adjust Tilt Function

NO

Replace Q321 And Related Components

YES

When Adjust CG Function, Is The Voltage Active At B301

NO

Check Q321/326/ Q322 And Related Circuit

YES

Replace CRT

End
15

16. OSD Abnormal OSD Abnormal

GD910T-1 Service Manual 16 o f 18

YES

Is OSD On The Screen ?

NO

Re-Initialize Default NO Value At U102

Is OSD On The Screen Rolling ?

Does OSD Video Waveform Appear At U701 # 1, # 2, # 3 ?

NO

Replace U201

YES

Check U101 Pin 52

NO

Does VSync Waveform Appear At U201 # 18 ?

YES

YES

Check B702 # 12

NO

Does HSync Waveform Appear At U201 #5?

Replace U701

YES

Replace U201 And Related Components

End

16

GD910T-1 Service Manual 17. NO POWER Start 17 of 18

Check & Fix 200V/ 75V Line Of Video/ Hor. CKT.

NO

Is 200V/78V Output Short ?

Output Short To The Ground Check

YES

Check & Fix F901, BD901,NTC901

NO

Is DC Input C907 >150V ?
YES

Bridge Output Check

Replace U901 And Related Components

NO

Is Sguare Wave of U901 # 6 Good ?

Switching Square Wave Check

YES

Replace T901 And Related Components

NO

Are 200V,78V, 41V,16.5V and 6.3V Good

VDC. Output Check

YES

Check & Fix T902 And F.B.T.

NO

Does H-sync. Appear at Emitter of Q904 ?

Hor. Sync. Check

YES

End

17

18. Power Saving Failure

GD910T-1 Service Manual 18 of 18

Power Saving NG

Is Suspend Function Good ?

NG

Is MCAI0 ?

NO

YES

YES

Are Q911 and Q912 Check Good ?
NO

OK

OK

Replace Q911 and Q912

Is MCAO0V ?

NO

Is U101 Checked Good ?

YES

Are Q908 and U912 Checked Good ?

NO

Replace Q908,U912
YES

YES

End

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