How to troubleshoot the power board of TCL L37M61 and TCLL42M64 LCD TVs
Alignment Procedure – Service mode: To enter the factory mode
1.press the vol.- botton to 0 , enter the “picture” menu,cursor place the “ contrast”, input the digits 9735.
2. When using the heat key to open the factory menu , press the Freeze key if it is not the menu .
Factory menu white balance adjust and HDMI signal source inspection
It is only adjusting white balance of the HDMI signal source Adjustment in HDMI mode
1. Input HDMI signal: timing is 720P, Patter is 10 grey
2. enter the factory menu, select white balance item, press OK key , system auto covering to HDMI signal source, and so on setting the color temperature item is standard 3. adjusting the white balance machine ,setting the color coordinate to adjust the color temperature
4. press OK key to auto adjusting, until cuing is finishing
5. Looking into the fugue and screen menu , estimating screen menu or not in gear, exit the factory menu and inspecting the HDMI signal source
Accessory 1: all the displaying item signification.
2. When using the heat key to open the factory menu , press the Freeze key if it is not the menu .
Factory menu white balance adjust and HDMI signal source inspection
It is only adjusting white balance of the HDMI signal source Adjustment in HDMI mode
1. Input HDMI signal: timing is 720P, Patter is 10 grey
2. enter the factory menu, select white balance item, press OK key , system auto covering to HDMI signal source, and so on setting the color temperature item is standard 3. adjusting the white balance machine ,setting the color coordinate to adjust the color temperature
4. press OK key to auto adjusting, until cuing is finishing
5. Looking into the fugue and screen menu , estimating screen menu or not in gear, exit the factory menu and inspecting the HDMI signal source
Accessory 1: all the displaying item signification.
X/y: about standard color temperature of the color coordinate, it is manual setting before adjusting the white balance.
Manual adjustment mode
The cursor placed to x or y,press “OK” key to enter manual adjustment of the white balance
(2).the ADC in the factory menu is been adjusted and inspecting YpbPr /VGA/AV signal source only auto adjusting the YpbPr/VGA/AV signal source ,all signal source adjustment mode as follows:
1.YpbPr
a. switching to YpbPr signal source ,input the 720@60 contrast of 100% eight grey-scale/color –bar signal reference machine model: timing81 of bsg360a, pattern85
b. enter the ADC of the factory menu item press OK key to auto adjusting
c. after cuing auto adjustment successfully,observing displaying figure and screen menu or not in gear, exit the factory menu and inspect the YpbPr signal source.
The cursor placed to x or y,press “OK” key to enter manual adjustment of the white balance
(2).the ADC in the factory menu is been adjusted and inspecting YpbPr /VGA/AV signal source only auto adjusting the YpbPr/VGA/AV signal source ,all signal source adjustment mode as follows:
1.YpbPr
a. switching to YpbPr signal source ,input the 720@60 contrast of 100% eight grey-scale/color –bar signal reference machine model: timing81 of bsg360a, pattern85
b. enter the ADC of the factory menu item press OK key to auto adjusting
c. after cuing auto adjustment successfully,observing displaying figure and screen menu or not in gear, exit the factory menu and inspect the YpbPr signal source.
2.VGA
a. Switching to VGA signal source , input 1024x768@60Hz 16 grey or 10 grey reference machine model: BSG360A of Timing13,pattern105
b. enter the factory menu ADC item ,press ok key to auto adjusting
c. after cuing auto adjustment successfully, observing successfully, observing displaying fugue and screen menu or not in gear, exit the factory menu and inspect the VGA signal source
3.AV
d. Switching to AV signal source , input PAL 100% saturation of the 8 grey signal source reference machine model: BSG360A of Timing,pattern 85
e. enter the factory menu ADC item ,press OK key to auto adjusting
f. after cuing auto adjustment successfully, observing successfully, observing displaying figure and screen menu or not in gear, exit the factory menu and inspect the AV signal source.
4 Inspect ATV/DTV signal source parting switch to ATV or DTV ,and then scanning,observing or not losing channel and the picture displaying and volume in gear or not
5 the factory menu function setting.
a. Switching to VGA signal source , input 1024x768@60Hz 16 grey or 10 grey reference machine model: BSG360A of Timing13,pattern105
b. enter the factory menu ADC item ,press ok key to auto adjusting
c. after cuing auto adjustment successfully, observing successfully, observing displaying fugue and screen menu or not in gear, exit the factory menu and inspect the VGA signal source
3.AV
d. Switching to AV signal source , input PAL 100% saturation of the 8 grey signal source reference machine model: BSG360A of Timing,pattern 85
e. enter the factory menu ADC item ,press OK key to auto adjusting
f. after cuing auto adjustment successfully, observing successfully, observing displaying figure and screen menu or not in gear, exit the factory menu and inspect the AV signal source.
4 Inspect ATV/DTV signal source parting switch to ATV or DTV ,and then scanning,observing or not losing channel and the picture displaying and volume in gear or not
5 the factory menu function setting.
1) according to so you saying item: enactment LCD panel factory appellation, factory menu heat key setting to OFF, hotel mode setting to off; Electrify mode setting to STB
2) select factory init item, press OK key to initialization operating about boot-strap
WARNING: during finishing the Factory init operating to packing , if the TV has been boot-strapped , the TV must operate again before packing.
2) select factory init item, press OK key to initialization operating about boot-strap
WARNING: during finishing the Factory init operating to packing , if the TV has been boot-strapped , the TV must operate again before packing.
SMPS schematic: Standby circuit working
When switching on ,at first the standby circuit work. Supply 5V to the figure board , the main power start working when receiving the figure board boot-strap signal. Output: 24v12v300v volts d.c. pass the D810R832and then transformer(T803) primary coil， there into 3 pin connect pin 567 of U4 VDDfrom U4 sourcedrain put throughand so that the transformer(T803) primary coil put through telepathy secondary 9 pin outputting through D807 commute 5VStandby voltageR838 sampling 5v voltageconnect sampling 5Vconnect to pin 1 TLHPC92 therepathy U3 pin 34 put through leave each other Connect from the signal to U4 PIN 34control U4 outputting and so that the transformer output the steady 5v
At the same timethe transformer T803 primary coil 4 pin divide into two-way outputting
1one-way output 15v to the VCC，supply to IC supplying power
2one-way output to U4 supply power.
At the same timethe transformer T803 primary coil 4 pin divide into two-way outputting
1one-way output 15v to the VCC，supply to IC supplying power
2one-way output to U4 supply power.
Switch on work flow
It passes R842R841D819 when receiving the figure board outputting the switch on high level signal and then send to Q808 BaseQ808 break over TLU2 -1 2 pin break overthe signal coupling to TL U2 pin 34. At the same time Q807 cut offTLU2 pin 1 - 2 disconnectionnot coupling the signal to TLU2 pin 3 4. At the same time Q807 cut off15V cannot supply through the Q807 outputting the VCCU5 and U6 stop working if they cannot receive the supply power.
It passes R842R841D819 when receiving the figure board outputting the switch on high level signal and then send to Q808 BaseQ808 break over TLU2 -1 2 pin break overthe signal coupling to TL U2 pin 34. At the same time Q807 cut offTLU2 pin 1 - 2 disconnectionnot coupling the signal to TLU2 pin 3 4. At the same time Q807 cut off15V cannot supply through the Q807 outputting the VCCU5 and U6 stop working if they cannot receive the supply power.
PFC circuit
15V ingress and U6 startup,P7 OUTPUT CONTROLLING Q801 CUT OFF AND BREAK OVER L801 is energy storage constantly commute the voltage Upgrade the 380V or not , pass the C807 filter, outputting to PWM circuit.
PWM circuit
After 15v enter u5 pin P6, U5 start working, p5 output the pulse signal control Q805 and Q802 basewhen the pulse signal is high level,Q805 cut offQ803 break overVCC pass though the Q802 and R813 to charge up C820. when the pulse signal is low level,Q805 break overQ803 cut offC802 pass though Q820 discharge . on account of C820 overlap cycle charge and dischargeon account of T802 secondary coil coupling to signal variety,and so that control Q803 AND Q806 cut off and disconnect. In this way PFC Circuit output voltage connecting the transform T801 primary coilalso repeat constantly deposited entry and released energy exchange course , and then telepathy to secondary coil and output voltage: 12v24v 12V and 24V steady circuit. Pass through R811 sampling 24v and R808 sampling 12v,sampling the signal passing through U1 telepathy controlling U5 PIN P2 ,adjust U5 PIN P5 Output the pulse width adjust T801 output.
Overvoltage protect: When the voltage is over and sampling signal mix through D809、R856 , the high level send to Q812 base，at the same time Q810 collector is high level.
Q810 is break overthrough D820 connect to R842the potential alter low level the switch on signal high level can not operateTV starts standby.
Q810 is break overthrough D820 connect to R842the potential alter low level the switch on signal high level can not operateTV starts standby.
Low-voltage protect: When it is in gear about 24v , 24v through R1004R1005R1006 change the voltagethe Q1001 break-overQ1001 collector is lower level.
When the voltage is lower 24v, D1002 cannot break –overQ1001 collector is high level ,D1001 and Q812 break-over switch-on signal voltage change lower, TV shift standby.
When the voltage is lower 24v, D1002 cannot break –overQ1001 collector is high level ,D1001 and Q812 break-over switch-on signal voltage change lower, TV shift standby.
SMPS schematic
SMPS troubleshooting procedure
SMPS faults: No voltage
Analysis and detect: at first testing the switching on p802 gain 2.2v switching on voltage in power board, constant the power is ontesting 12v and 24v is 0v，measuring 5v is in gear. Showing the TV can standby in gear. If measuring 12v and 24v is 0Vthe problem cause is 12v and 24v commonality part.
12v and 24v commonality part is PFC part and power PWN part over current and voltage protect part. At first measure L809 PFC voltage. If it discovering 380v is 0Vthe problem is PFCcontact the PWM problem , primary analyzing cause is 15V circuitU5 and U6 can not work when only 15V has not in gear.
We know: the transformer T803 secondary coil 4 pin output second part:
1. one way output 15V to VCCsupply to ic power supply
2. one way to U4 supply powersupply to 5VSTB
because 5V is in gearIC power supply is 15Vmeasure R826 VCC outputting voltage is 0V. measure R826 resistance to GND is in gear. And then measuring Q807 transmit is not voltage. Measure D824discovering one pin has voltage measure D824 discover the D824 disconnectionreplace the D824the voltage is ok.
Analysis and detect: at first testing the switching on p802 gain 2.2v switching on voltage in power board, constant the power is ontesting 12v and 24v is 0v，measuring 5v is in gear. Showing the TV can standby in gear. If measuring 12v and 24v is 0Vthe problem cause is 12v and 24v commonality part.
12v and 24v commonality part is PFC part and power PWN part over current and voltage protect part. At first measure L809 PFC voltage. If it discovering 380v is 0Vthe problem is PFCcontact the PWM problem , primary analyzing cause is 15V circuitU5 and U6 can not work when only 15V has not in gear.
We know: the transformer T803 secondary coil 4 pin output second part:
1. one way output 15V to VCCsupply to ic power supply
2. one way to U4 supply powersupply to 5VSTB
because 5V is in gearIC power supply is 15Vmeasure R826 VCC outputting voltage is 0V. measure R826 resistance to GND is in gear. And then measuring Q807 transmit is not voltage. Measure D824discovering one pin has voltage measure D824 discover the D824 disconnectionreplace the D824the voltage is ok.
No voltage
Analysis and detect: at first testing the switching onp802 gain 2.2v switching on voltage in power board, constant the power is ontesting 12v and 24v is 0vmeasuring 5v is in gear. Showing the TV can standby in gear. Measuring 12v and 24v is 0V, the problem cause is 12v and 24v commonality part.
12v and 24v commonality part isPFC part and power PWN part over current and voltage protect part. At first is there 15V of VCC Is there Q807 Transistor of 13V. U2 has not gain the switch on controlling signal. Disconnect D820and than measure now avoid the problem of over current and voltage the problem is the switch on signal has not effect. Constant switch on signal has inputted the P802testing discover R842 disconnectionthe Switch on signal has not send to the Q808replace R842The TV switch on testing，the fault avoid.
Analysis and detect: at first testing the switching onp802 gain 2.2v switching on voltage in power board, constant the power is ontesting 12v and 24v is 0vmeasuring 5v is in gear. Showing the TV can standby in gear. Measuring 12v and 24v is 0V, the problem cause is 12v and 24v commonality part.
12v and 24v commonality part isPFC part and power PWN part over current and voltage protect part. At first is there 15V of VCC Is there Q807 Transistor of 13V. U2 has not gain the switch on controlling signal. Disconnect D820and than measure now avoid the problem of over current and voltage the problem is the switch on signal has not effect. Constant switch on signal has inputted the P802testing discover R842 disconnectionthe Switch on signal has not send to the Q808replace R842The TV switch on testing，the fault avoid.
No voltage
Analysis and detect: at first testing the switching on，p802 gain 2.2v switching on voltage in power board, constant the power is ontesting 12v and 24v is 0vmeasuring 5v is in gear. Showing the TV can standby in gear. If measuring 12v and 24v is 0Vthe problem cause is 12v and 24v commonality part.
Analysis and detect: at first testing the switching on，p802 gain 2.2v switching on voltage in power board, constant the power is ontesting 12v and 24v is 0vmeasuring 5v is in gear. Showing the TV can standby in gear. If measuring 12v and 24v is 0Vthe problem cause is 12v and 24v commonality part.
12v and 24v commonality part isPFC part and power PWN part over current and voltage protect part.
At first disconnect D820 affirm where the problem is part and then measure 13V of VCC if it is in gearcontinue testing PFC voltage is in gear，
So that determinant the problem is protect circuitmeasuring D820 cathode to GND resistancediscovery resistance is littler than in gear testing Protect circuitdiscovery Q812 short circuit attain. Replacing the Q812 ,the TV is ok.
At first disconnect D820 affirm where the problem is part and then measure 13V of VCC if it is in gearcontinue testing PFC voltage is in gear，
So that determinant the problem is protect circuitmeasuring D820 cathode to GND resistancediscovery resistance is littler than in gear testing Protect circuitdiscovery Q812 short circuit attain. Replacing the Q812 ,the TV is ok.
Switch on voltage moment，12V testing point is 20V24V testing point is 30V. fall to 0.4V or not moment .
Analysis and detect: at first testing the switching onp802 gain 2.2v switching on voltage in power board, constant the power is onswitch on voltage moment12V testing point is 20V,24V testing point is 30V.fall to 0.4V or not moment .measuring 5V is in gearthe TV can standby in gearthe problem is 12V and 24V steadfast voltage pass from R811 sampling 24V and R808 sampling 12Vsampling signal pass though telepathy controlling U5 pin P5, and then output the pulse widthadjust T801 outputting.
Detecting 12V and 24V steadfast voltage partdiscovering Q804 is bad, replace it the fault rectified.
Analysis and detect: at first testing the switching onp802 gain 2.2v switching on voltage in power board, constant the power is onswitch on voltage moment12V testing point is 20V,24V testing point is 30V.fall to 0.4V or not moment .measuring 5V is in gearthe TV can standby in gearthe problem is 12V and 24V steadfast voltage pass from R811 sampling 24V and R808 sampling 12Vsampling signal pass though telepathy controlling U5 pin P5, and then output the pulse widthadjust T801 outputting.
Detecting 12V and 24V steadfast voltage partdiscovering Q804 is bad, replace it the fault rectified.
When5V, dithering, and the output is 4V, no voltage at 12 V and 24V
Analysis, examine and repair: Open the panel and test, find out when 5V, dithering, the output is 4V, and no output at other voltage, it means there is something wrong with standby, it can’t export the stable 5V standby voltage.
At first, Check whether the commute bridge exports voltage: measure and find out there is 300 V direct current in D810, then check U4 to find out whether it starts work, measure the start voltage of U4 at first. There is dithering in 11V, but 13V is normal, the matter is in support part of work voltage, measure pin 4 voltage output of D803,there has voltage, measure D822, it is no voltage, then measure R847, find out there is plough, exchange it and eliminates the malfunction.
Analysis, examine and repair: Open the panel and test, find out when 5V, dithering, the output is 4V, and no output at other voltage, it means there is something wrong with standby, it can’t export the stable 5V standby voltage.
At first, Check whether the commute bridge exports voltage: measure and find out there is 300 V direct current in D810, then check U4 to find out whether it starts work, measure the start voltage of U4 at first. There is dithering in 11V, but 13V is normal, the matter is in support part of work voltage, measure pin 4 voltage output of D803,there has voltage, measure D822, it is no voltage, then measure R847, find out there is plough, exchange it and eliminates the malfunction.
No voltage at 5V, 12 V and 24V.
Analysis, examine and repair: open the panel and test, there is no voltage, means the machine has something wrong with standby, it can’t output the 5V standby voltage, so it can’t produce 12V and 24V.
Check whether the commute bridge exports voltage: measure and find out there is 300V direct current in D810,then check U4 to find out whether it starts work,
measure the start voltage of U4 at first. There is dithering in 6-7V, but 13V is normal, measure 4 feet voltage output of D803, there has voltage, measure D822, it is
7V, find out no output when test D824,shows that it can’t run normally when at 5V , so exchange the U4, malfunction disappears.
Analysis, examine and repair: open the panel and test, there is no voltage, means the machine has something wrong with standby, it can’t output the 5V standby voltage, so it can’t produce 12V and 24V.
Check whether the commute bridge exports voltage: measure and find out there is 300V direct current in D810,then check U4 to find out whether it starts work,
measure the start voltage of U4 at first. There is dithering in 6-7V, but 13V is normal, measure 4 feet voltage output of D803, there has voltage, measure D822, it is
7V, find out no output when test D824,shows that it can’t run normally when at 5V , so exchange the U4, malfunction disappears.
No voltage for 12V and 14V.
Analysis, examine and repair: open the machine and test at first, find out when standby at 5V voltage is normal means no problem with standby, provide the 2.2V start voltage, no voltage output, so there is something wrong with the 12V and 14V voltage part, maybe the problem appears in PFC, PWM and protective circuit.
Measure the output voltage of VCC, 12V in R836, at this time there is noise in transformer, it is the voltage output reducing, maybe there is something wrong with the protective circuit, then cut D820 of protective circuit, test again, there is normal voltage output, so it can conclude that the problem is in protective circuit, the problem is over current and voltage or low-voltage 、low-current protect circuit。Cut the protect point after connect the D820, voltage goes back to normal when cuts the D1001, then test the low-voltage protect circuit , Q1001 is plough, exchange it and the malfunction disappears.
The TV has no power
Analysis, examine and repair: open the machine and test at first, find out when standby at 5V voltage is normal means no problem with standby, provide the 2.2V start voltage, no voltage output, so there is something wrong with the 12V and 14V voltage part, maybe the problem appears in PFC, PWM and protective circuit.
Measure the output voltage of VCC, 12V in R836, at this time there is noise in transformer, it is the voltage output reducing, maybe there is something wrong with the protective circuit, then cut D820 of protective circuit, test again, there is normal voltage output, so it can conclude that the problem is in protective circuit, the problem is over current and voltage or low-voltage 、low-current protect circuit。Cut the protect point after connect the D820, voltage goes back to normal when cuts the D1001, then test the low-voltage protect circuit , Q1001 is plough, exchange it and the malfunction disappears.
The TV has no power
Analysis, examine and repair: check the machine first, find out the fuse is cut and no obvious component burned-out mark, circuitry has over current or voltage circuit since the fuse is burned, means there is short circuit in somewhere. Measure and find out the Q801 has been short circuit, no short circuit finding in other parts, exchange the Q801, test against, 5V voltage is normal, but no output at 12V -24V, because the PFC is broken, the voltage output of PFC is only about 320V, PFC doesn’t run, the power supply voltage of PFC at 14V, it is normal, so decide to exchange U6, the malfunction is still here, measure each feet against floor resistance of U6 in turn, find out the R869 is plough, exchange and test, eliminates malfunction, the fact is that R869 disconnect caused the U6 over current protect circuit runsU6 stop the output, so there is no voltage output of PFC, and no voltage.
No voltage for 12V and 14V.
Analysis, examine and repair: open the panel and test at first, find out when standby at 5 V, the voltage is normal, means no problem with standby, then provide 2.2 V start voltage, make out no output at12V and 14V. The TV is standby.
Problem both at 12V and 14V voltage, maybe there is some matter with PFC, PWM and protective circuit, so measure output of PFC first, it is 320V, means PFC doesn’t work, cut down the protective circuit, start the machine to test the output on 12V and 14V voltage, it is normal, so the problem appears in protective circuit, cut down the over current protect point separately to test , malfunction still, then cut down the exceed press protect, malfunction still,too, cut down the low-voltage protect Q1001 at last, malfunction disappears, and none of base voltage with Q1001, test and find out that 24V low-voltage protect sampling resistance R1004 disconnection. Open the machine after exchange it, malfunction disappears.
Analysis, examine and repair: open the panel and test at first, find out when standby at 5 V, the voltage is normal, means no problem with standby, then provide 2.2 V start voltage, make out no output at12V and 14V. The TV is standby.
Problem both at 12V and 14V voltage, maybe there is some matter with PFC, PWM and protective circuit, so measure output of PFC first, it is 320V, means PFC doesn’t work, cut down the protective circuit, start the machine to test the output on 12V and 14V voltage, it is normal, so the problem appears in protective circuit, cut down the over current protect point separately to test , malfunction still, then cut down the exceed press protect, malfunction still,too, cut down the low-voltage protect Q1001 at last, malfunction disappears, and none of base voltage with Q1001, test and find out that 24V low-voltage protect sampling resistance R1004 disconnection. Open the machine after exchange it, malfunction disappears.
No voltage for 12V and 14V.
Analysis, examine and repair: open the panel and test at first, find out when standby at 5 V, the voltage is normal, means no problem with standby, then provide 2.2 V start voltage, make out no output at 12V and 14V. The machine is standby, problem appears both at 12V and 14V voltage, maybe there is some matter with PFC, PWM and protective circuit, so measure output of PFC first, if is 380 V, means PFC runs normally. It can conclude that problem is at 12V and 14V voltage part.
Since no voltage for both at 12V and 14V, the chance that feedback loop gets in trouble is not big, check the PWM circuit first, examine the going of U5, check whether there is drive voltage of pin P5 on U5,dittering on 1.5V more or less is normal. Then measure against floor resistance of P5 on U5, cut down the outing circuit, short circuit, it can conclude that U5 has been broken, open after exchange it, find out that the malfunction disappears.
Analysis, examine and repair: open the panel and test at first, find out when standby at 5 V, the voltage is normal, means no problem with standby, then provide 2.2 V start voltage, make out no output at 12V and 14V. The machine is standby, problem appears both at 12V and 14V voltage, maybe there is some matter with PFC, PWM and protective circuit, so measure output of PFC first, if is 380 V, means PFC runs normally. It can conclude that problem is at 12V and 14V voltage part.
Since no voltage for both at 12V and 14V, the chance that feedback loop gets in trouble is not big, check the PWM circuit first, examine the going of U5, check whether there is drive voltage of pin P5 on U5,dittering on 1.5V more or less is normal. Then measure against floor resistance of P5 on U5, cut down the outing circuit, short circuit, it can conclude that U5 has been broken, open after exchange it, find out that the malfunction disappears.