How to troubleshoot the power board of TCL L37M61 and TCL L42M64 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.
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.
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 for 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 for 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.
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: 24v 12v 300v volts d.c. pass the
D810 R832 and then transformer(T803) primary coil， there into 3 pin connect pin 5 6 7 of U4 VDD from U4 source drain put through and so
that the transformer(T803) primary coil put through telepathy
secondary 9 pin outputting through D807 commute 5V
Standby voltage R838 sampling 5v voltage connect
sampling 5V connect to pin 1 TLHPC92
therepathy U3 pin 3 4 put through leave
each other Connect from the signal to U4 PIN 3 4 control U4 outputting and so
that the transformer output the steady 5v.
At the same time the transformer T803 primary coil 4 pin divide into two-way outputting. 1 one-way output 15v to the VCC， supply to IC supplying power.
2 one-way output to U4 supply power.
At the same time the transformer T803 primary coil 4 pin divide into two-way outputting. 1 one-way output 15v to the VCC， supply to IC supplying power.
2 one-way output to U4 supply power.
Switch - On work flow.
It passes R842 R841 D819 when receiving the figure board outputting the switch on high level signal and then send to Q808 Base Q808 break over TLU2 -1 2 pin break over the signal coupling to TL U2 pin 3 4. At the same time Q807 cut off TLU2 pin 1 - 2 disconnection not coupling the signal to TLU2 pin 3 4. At the same time Q807 cut off 15V cannot supply through the Q807 outputting the VCC U5 and U6 stop working if they cannot receive the supply power.
It passes R842 R841 D819 when receiving the figure board outputting the switch on high level signal and then send to Q808 Base Q808 break over TLU2 -1 2 pin break over the signal coupling to TL U2 pin 3 4. At the same time Q807 cut off TLU2 pin 1 - 2 disconnection not coupling the signal to TLU2 pin 3 4. At the same time Q807 cut off 15V cannot supply through the Q807 outputting the VCC U5 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 base when
the pulse signal is high level,Q805 cut off Q803 break over VCC pass though the Q802 and R813 to charge up C820. when the pulse signal is low level,Q805
break over Q803
cut off C802
pass though Q820 discharge . on account of C820 overlap cycle charge and
discharge on
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 coil also repeat constantly deposited entry and released energy exchange course , and then telepathy to secondary coil and output
voltage: 12v 24v
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 over through D820 connect to R842 the potential alter low level the switch on signal high level can not operate TV starts standby.
Q810 is break over through D820 connect to R842 the potential alter low level the switch on signal high level can not operate TV starts standby.
Low-voltage
protect: When it is in gear about 24v , 24v
through R1004 R1005 R1006 change the voltage the Q1001 break-over Q1001 collector is lower level.
When the voltage is lower 24v, D1002 cannot break –over Q1001 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 –over Q1001 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 on testing 12v and 24v is 0v， measuring 5v is in gear. Showing the TV can standby in gear. If measuring 12v and 24v is 0V the 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 0V the problem is PFC contact the PWM problem , primary analyzing cause is 15V circuit U5 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 VCC supply to ic power supply
2. one way to U4 supply power supply to 5VSTB because 5V is in gear IC power supply is 15V measure R826 VCC outputting voltage is 0V. measure R826 resistance to GND is in gear. And then measuring Q807 transmit is not voltage. Measure D824 discovering one pin has voltage measure D824 discover the D824 disconnection replace the D824 the 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 on testing 12v and 24v is 0v， measuring 5v is in gear. Showing the TV can standby in gear. If measuring 12v and 24v is 0V the 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 0V the problem is PFC contact the PWM problem , primary analyzing cause is 15V circuit U5 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 VCC supply to ic power supply
2. one way to U4 supply power supply to 5VSTB because 5V is in gear IC power supply is 15V measure R826 VCC outputting voltage is 0V. measure R826 resistance to GND is in gear. And then measuring Q807 transmit is not voltage. Measure D824 discovering one pin has voltage measure D824 discover the D824 disconnection replace the D824 the voltage is ok.
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 on testing 12v and 24v is 0v measuring 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 is PFC 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 D820 and 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 P802 testing discover R842 disconnection the Switch on signal has not send to the Q808 replace R842 The TV switch on testing， the fault avoid.
Analysis and detect: at first testing the switching on p802 gain 2.2v switching on voltage in power board, constant the power is on testing 12v and 24v is 0v measuring 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 is PFC 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 D820 and 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 P802 testing discover R842 disconnection the Switch on signal has not send to the Q808 replace R842 The 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 on testing 12v and 24v is 0v measuring 5v is in gear. Showing the TV can standby in gear. If measuring 12v and 24v is 0V the 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 on testing 12v and 24v is 0v measuring 5v is in gear. Showing the TV can standby in gear. If measuring 12v and 24v is 0V the 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 disconnect D820 affirm where the problem is part and then measure 13V of VCC if it is in gear continue testing PFC voltage is in gear，
So that determinant the problem is protect circuit measuring D820 cathode to GND resistance discovery resistance is littler than in gear testing Protect circuit discovery 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 gear continue testing PFC voltage is in gear，
So that determinant the problem is protect circuit measuring D820 cathode to GND resistance discovery resistance is littler than in gear testing Protect circuit discovery Q812 short circuit attain. Replacing the Q812 ,the TV is ok.
Switch
on voltage moment， 12V testing point is 20V 24V testing point is 30V. fall to 0.4V or not moment
.
Analysis and detect: at first testing the switching on p802 gain 2.2v switching on voltage in power board, constant the power is on switch on voltage moment 12V testing point is 20V,24V testing point is 30V. fall to 0.4V or not moment .measuring 5V is in gear the TV can standby in gear the problem is 12V and 24V steadfast voltage pass from R811 sampling 24V and R808 sampling 12V sampling signal pass though telepathy controlling U5 pin P5, and then output the pulse width adjust T801 outputting.
Detecting 12V and 24V steadfast voltage part discovering Q804 is bad, replace it the fault rectified.
Analysis and detect: at first testing the switching on p802 gain 2.2v switching on voltage in power board, constant the power is on switch on voltage moment 12V testing point is 20V,24V testing point is 30V. fall to 0.4V or not moment .measuring 5V is in gear the TV can standby in gear the problem is 12V and 24V steadfast voltage pass from R811 sampling 24V and R808 sampling 12V sampling signal pass though telepathy controlling U5 pin P5, and then output the pulse width adjust T801 outputting.
Detecting 12V and 24V steadfast voltage part discovering 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
runs U6 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.