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Toshiba 1997 G Series, Troubleshooting Manual

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Toshiba 1997 G Series Troubleshooting Manual Download Page 23

21

JRS  12-97

3.  +30 Volt Over Voltage Protect.
When the supply voltage goes beyond the zener votage,
the zener diode conducts and delivers a voltage to the
anode of D 863.  This passes through the diode switch,
D863, to pin 14 of Z801, and shut down takes place.

Figure 15.   +30V Over Voltage Protect.

Normal voltage at the monitor point is about 0.  A volt-
age of about 2.5V or greater will result in shut down.

Figure 16.   +15V Over Voltage Protect.

4.  +15V Over Voltage Protect.
The +15V over voltage protect operates in a similar fash-
ion as the +30V over votage protect.

Summary of Contents for 1997 G Series

Page 1: ...SERVICE TRAINING 1997 G SERIES COLOR TELEVISION POWER SUPPLY AND SHUTDOWN TROUBLESHOOTING GUIDE ...

Page 2: ...EN SUPPLY 12 10 SUB POWER SUPPLY 14 11 SUB POWER SUPPLY TROUBLESHOOTING GUIDE 16 SHUT DOWN CIRCUITS 17 1 SUMMARY OF SHUT DOWN CIRCUITS 18 2 POWER SHUT DOWN TROUBLESHOOTING GUIDE 20 3 30 Volt Over Voltage Protect 21 4 15V Over Voltage Protect 21 5 30 V Over Current Protect 22 6 15V Over Current Protect 22 7 15V Over Current Protect 23 8 35V Over Current Protect 23 9 15V Under Voltage Protect 24 10 ...

Page 3: ...1 POWER SUPPLY CIRCUIT ...

Page 4: ...highly efficient and reliable F801 T801 T802 T840 POWER TRANS TPW 1549AZ 12V D840 Q840 REG 5V 1 MICROCOMPUTER SR81 F860 R861 D801 T862 TPW 3332AS CONVERTER TRANS Q801 VOLTAGE CONTROL STR Z3201 Q843 SW Q830 SW Q862 PHOTO COUPLER 12V 38V Q840 REG Q840 REG Q840 REG 5V 2 TUNER COMB V C D etc 5V 3 PIP ESD C C RGB SW 9V 2 COMB DSP CRT D etc AUDIO OUT H Vcc V C D 9V Q430 R470 R479 R471 F470 R101 F B T V ...

Page 5: ...in 4 Reset occurs when power is first applied to Q840 The 5V on pin 5 comes up first while pin 4 stays low This is the reset condi tion After C843 fully charges pin 4 goes to 5V for normal operation 3 Main Power Supply 1 Main Power Rectifier Circuit D801 and C810 the rectifier and filter for the main switching supply produce 165V R810 suppresses the rush current at turn on SR81 is a relay that tur...

Page 6: ...LC Series Resonant Circuit The LC series resonant switch mode power supply is a frequency regulated power supply operating above reso nance When the the load increases on the secondary side of the transformer the frequency decreases oper ates closer to resonance and the current increases Con versely when the load decreases the frequency increases and the current decreases VL v e Resonant point Fre...

Page 7: ...terminal 8 CD Capacitor for delay latch ON OFF terminal 9 VCC Power source terminal for control section 10 DRI VCC Gate drive power supply output terminal 11 OC Over current detect terminal 12 COM Half bridge GND 14 OUT Half bridge output 15 VB High side gate drive power source input STR Z415 STR Z415 and STR Z4201 Block Diagram 9 15 6 1 14 12 10 2 3 4 5 7 11 8 CD OC Vcc VB VIN OUT COM TSD OVP STA...

Page 8: ...OSFETs see OSC OUT SIGNAL waveform of Figure 7 The lowest oscillation frequency is deter mined by capacitor C862 and resistor R867 4 Frequency Control Current flowing out of the CONT terminal Pin 5 var ies the charging time of oscillator capacitor C862 which in turn controls the frequency of the Output Pin 14 signal The control current is determined by the photocoupler The photocoupler phototransi...

Page 9: ...C862 R867 C867 R866 C874 R870 C870 D886 D855 Audio output 15 13 11 12 3 2 D884 D883 T862 C865 C863 D875 C871 R861 R862 D862 D864 R871 10 C884 Q862 R883 C891 R891 Z801 MAIN OUTPUT TSD OVP DELAY LATCH REF OC OSC OSC CONTROL ERROR AMP 4 5 14 CD OC C868 D872 6 R868 START Logic Fmax 10 C873 D873 R872 Actual Circuit ...

Page 10: ... gate voltage ON OFF OFF ON Pin14 Push pull output voltage OA OV VIN terminal voltage Pin 1 VG H Pin 14 Push pull output current Voltages On IC801 Using a 100 W light bulb as a Losd Pin Voltage Pin Voltage 1 150 Vdc 9 17 7 Vdc 2 0 Vdc 10 7 8 Vdc 3 5 8 Vdc 11 0 9 Vdc 4 2 3 Vdc 12 0 Vdc 5 5 8 Vdc 13 NC 6 5 8 Vdc 14 75 Vdc 7 3 6 Vdc 15 83 Vdc 8 0 4 Vdc ...

Page 11: ... the relay engage No Check Sub Power supply Microprocessor and Relay drive circuits Does the TV go into shutdown Yes Yes No Is the B at F470 Low or at 0v 0V Check start up voltage and 165V on IC 801 If missing Check F860 D801 SR81 and surrounding compnonets If 165V and Start up are present Power Supply Troubleshooting Guide Main B is 140V 150V Freq at pin 14 if IC801 is 136KHz Main B reaches 155 t...

Page 12: ...ooped circuit In order to troubleshoot the circuit the loop must be broken By interrupting the feedback portion of the loop it can be determined if a problem exists in the primary or second ary side of the supply Table 3 and 4 shows the switch ing frequencies of IC801 and the secondary voltages of the supply with various feedbacks If the main supply is not regulating properly open F470 and check t...

Page 13: ...62 D864 R871 TSD OVP DELAY LATCH REF OC OSC OSC CONTROL 4 5 CD OC C868 D872 6 R868 START Logic Fmax 10 C873 D873 R872 Pre amp supply Latch Delay Drive Circuit Over current protect Oscillator Start up Resistor LC Resonance To prevent IC801 from going into over voltage protect during start up the charging of C869 will temporarily disable the latch When a DC voltage is applied to the cap it acts like...

Page 14: ...side DPC from pin 5 and 12V from pin 7 The 12V line produces a regulated 5V and 9V line The 5V supplies the tuner and PIP the 9V supplies the Video Processing Resistors and fuses are in each line for circuit protection 1 8 6 10 9 5 4 27V 27V 200V R642 C461 AFC BLANKING FBT ANODE HEATER FOCUS SCREEN ABL D460 B C448 Q404 Collector D406 C310 D302 R327 C317 12V 9V 7 2 3 FAIL SAFE R333 R433 F301 C421 Q...

Page 15: ...13 NOTES ...

Page 16: ...ff At that point the electromagnetic field across the Base Winding collapses supplies a negative voltage to the Base of Q1 and charges C1 The negative voltage on the Base of Q1 turns Q1 off The electromagnetic field on the primary collapses induces current in the secondary winding and induces a potential on the detection winding which continues to hold Base of Q1 low After the electomagnetic field...

Page 17: ...15 D848 R846 C845 C849 C856 D855 R857 R860 R859 Q851 Q852 4 2 1 5 3 L850 L851 C850 C851 R852 Q850 C853 C852 D849 R847 R858 C855 D850 D847 R851 D856 R850 160V R854 R853 D851 B IC 802 ...

Page 18: ...oring the 120V Note If IC802 is bad the feedback circuit must be checked Check for switching at pin 2 of IC801 If the switching is missing the Start up circuit maybe bad Check R852 for an open check Q851 Q850 and Q852 for shorts and check IC802 for a base emitter open on Q1 Lastly check T888 and C855 After re storing the switching check the feedback D856 R851 R820 and C853 If the switching is good...

Page 19: ...17 JRS 12 97 SHUT DOWN CIRCUITS ...

Page 20: ...te in a similar manner Normally all triggers are approximately zero volts When an ab normal condition occurs the appropriate shut down cir cuit triggers a high to pin 14 of Z801 Z801 sets and holds pin 16 low 0 volts This causes relay SR81 to de energize dropping all power in the TV except the standby power This means the trigger voltage also goes away There is now no means to determine which cir ...

Page 21: ...19 JRS 12 97 Figure 14 Summary of Shutdown circuits ...

Page 22: ...20 JRS 12 97 2 Power shut down troubleshooting guide ...

Page 23: ...asses through the diode switch D863 to pin 14 of Z801 and shut down takes place Figure 15 30V Over Voltage Protect Normal voltage at the monitor point is about 0 A volt age of about 2 5V or greater will result in shut down Figure 16 15V Over Voltage Protect 4 15V Over Voltage Protect The 15V over voltage protect operates in a similar fash ion as the 30V over votage protect ...

Page 24: ...light increase in voltage across R 7782 will turn on Q768 The collector then goes to about 30V This is the monitor point for shut down The normal collector voltage is Zero This trigger voltage will turn on Q758 It s collector will go low to about 0V This in turn causes transistor Q757 to turn off Q757 s collector rises to about 5V causing shut down to occur Figure 17 30V Over Current Protect 6 15V...

Page 25: ... cathode of Diode D302 The load current is carried through current sense resistor R370 If the load current exceeds a certain limit the voltage drop across R370 increases and turns on tran sistor Q370 When Q370 turns on the collector will go high towards the 35V supply This is the monitor point for shut down The Zener diode D370 goes into breakdown and a high voltage is delivered to pin 14 of Z801 ...

Page 26: ...53 will turn off and the collector will go high to about 5 This will pass through the diode switch D 866 and shut down will take place The 15V turns on transistor Q854 This causes the col lector of Q854 to go to about 15V If the 15V goes low Q854 will turn off the collector will go towards the 12V supply Thios will pass through the diode switch D867 and shut down will take place Figure 21 15V Unde...

Page 27: ... V sending the high to pin 14 of Z801 resulting in shut down Figure 22 200V Under Voltage Protect 11 X Ray High Voltage Protect The cathode of D885 is about 40V This developes a 25V reference to pin 11 of Z801 The cathode of D471 developes a nominal voltage of 22V to pin 13 of Z801 As long as the X Ray monitor point voltage is LESS than the reference voltage at pin 11 of Z801 operation is normal I...

Page 28: ...rent exceeds a certain level the increased voltage drop across R470 causes shut down to take place During normal operation the voltage drop across R470 is approximately 0 5V The turn on surge voltage drop is approximately 1 5V If the voltage across R470 exceeds about 1 8V shut down will occur Figure 24 125V Over Current Protect ...

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