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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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