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THOMSON TECHNICAL COMMUNICATION
Television
Troubleshooting Flow Chart
TFC-04049
The information contained herein is provided solely to assist qualified Technician in the diagnosis of the problem described. It is not intended as a modification or alteration of the product.
REVISION DATE: Chassis: CTC211 9/23/2004
TOPIC: High Voltage Troubleshooting SYMPTOM: No High Voltage
Warning!
To perform the troubleshooting in this flowchart, it may be necessary to defeat a safety circuit (scan loss). Make sure the CRT (s) are disconnected before attempting this procedure. Remember to restore all connections or components to normal condition before returning to the customer.
Place a short between base and emitter of Q14105. This will force on the run power supply and high voltage circuitry when AC is supplied.
1
Missing
Is the high voltage missing or low?
Low
2A
2B Check R14715, R14721, or U14104. If these test good, go to Run Power Supply troubleshooting TFC03112.
2C
Locate U14711 and check for 8.5VDC at pin 6. Is this voltage present?
No
Go to Page 3
Yes
Go to Page 2
Product Safety Information
Product Safety information is contained in the appropriate Thomson Service Data covering models/chassis referenced herein. All specified Product Safety requirements and testing shall be complied with prior to returning equipment to the customer. Servicers who defeat safety features or fail to perform safety checks may be liable for any resulting damages and may expose themselves and others to possible injury.
First Edition First Printing Copyright 2003 Thomson multimedia Inc. Printed in U.S.A. Trademark(s) ® Registered Marca(s) Registrada(s)
Page 1 of 3
THOMSON INC.
CTC211 High Voltage Troubleshooting
3
3A Check the voltage at the collector of Q14901. If this voltage is 0VDC, suspect a defective U14711. If the voltage is .7VDC or higher, check transistors Q14706, Q14903, and Q14902.
Check Pin 1 of U14711 for 6.2VDC. Is this voltage present?
No
Yes 4 4A Verify operation of Q14703, Q14704, and R14724. If these test ok and the waveform is still missing, suspect U14711.
Check for gate drive on Q14701 (14Vpp square wave). Is this waveform present?
No
Yes 5
Yes
Check the waveform (60Vpp horizontal pulse) on pin 5 of T14700. Is this waveform present?
Low
6
6A
6B Check the HVR B+ (110130VDC) at pin 1 of T14700. If the voltage is ok, check C14702 or suspect a defective T14700, Q14700, or Q14701. If the voltage Is low, go to next block
At the anode cup, check for 33KV with a high voltage probe. Is the voltage missing or low?
Missing
Suspect Defective T14700
Low
Low
Go to Page 3
Go to Page 3
Product Safety Information
Product Safety information is contained in the appropriate Thomson Service Data covering models/chassis referenced herein. All specified Product Safety requirements and testing shall be complied with prior to returning equipment to the customer. Servicers who defeat safety features or fail to perform safety checks may be liable for any resulting damages and may expose themselves and others to possible injury.
First Edition First Printing Copyright 2003 Thomson multimedia Inc. Printed in U.S.A. Trademark(s) ® Registered Marca(s) Registrada(s)
Page 2 of 3
THOMSON INC.
CTC211 High Voltage Troubleshooting
7
7A
Locate Q14751 and check for a drive waveform (20Vpp pulse) at the gate. Is this waveform missing?
No
Check for defective CR14751, CR14701, or Q14751.
Yes
8
8A Check CR14753, C14755, or shorted U14751. If these test ok, go to 17VDC source in the Run Power Supply.
Is the 17VDC present at pin 7 of U14751?
No
Yes 9 9A Check C14759 and C14719. If these test OK, check for reference 5VDC at pin 8. If this voltage is missing, suspect CR14755 or defective U14751
Check the waveform (7Vpp pulse) at pin 4 of U14751. Is this waveform present?
No
Yes 10 10A
Check for 5VDC reference at pin 8 of U14751. Is this voltage present?
No
Check for leaky C14754. If it checks ok, suspect defective U14751.
Yes 11
Suspect defective U14751.
Product Safety Information
Product Safety information is contained in the appropriate Thomson Service Data covering models/chassis referenced herein. All specified Product Safety requirements and testing shall be complied with prior to returning equipment to the customer. Servicers who defeat safety features or fail to perform safety checks may be liable for any resulting damages and may expose themselves and others to possible injury.
First Edition First Printing Copyright 2003 Thomson multimedia Inc. Printed in U.S.A. Trademark(s) ® Registered Marca(s) Registrada(s)
Page 3 of 3
THOMSON INC.