Collection How to Repair Hisense LCD/LED TV
1. How to Repair TV No Signal and AV have Display but No Sound Problem
Model: Hisense TLM2233 LCD TV
Chassis: MST6
Symptom: When in TV mode, the screen shows NO SIGNAL. Try using the AV signal input, got display but no sound.
Power on the Tv, screen display NO SIGNAL and it is showing the snow only. The whole Tv control on/off and other function normal. Try to search the TV channel and can’t find any TV signal! Changed to AV mode, the screen displays present perfectly but no sound. Even adjust the sound volume to maximum also not change.
Check the TV tuner 5V ok but the 33V missing. Check their tuning boost feedback circuit 12V got 0V! Found the service manual and check their audio section was using the same 12V line too. So both symptom of this lcd tv was causing by this 12V line became 0V.
So trace this 12V line on the mainboard and found this 12V line was supply from power supply secondary side and go through U23 (IRF7314) and reach to Tuner and audio section. This U23 function as a switching control and it can on or off the voltage output. After that measuring Q8 base pin for 0.6V normal, U23 pin 1 got 5V input and pin 7 & 8 output normal 5V. Again measuring Q12 base pin for 0.6V ok, then U23 pin3 no 12V input. After that measuring CN16 pin 5, pin6 got normal 12V supply.
Apparently the problem is in between 12V supply (CN16 pin 5 & 6) through U23 pin 3! Using multimeter ohm range, measure in between the CN16 pin 5 through U23 pin3, the meter reading it about 50+ ohm! If normal value it should be 0 or very low ohm. And this line ohm values sometimes can go to 100~300Kohm too! So the circuit line can get unstable ohm values, that’s mean the circuit was intermittently break line. Check the printed circuit board and found the line have circuit hole across PCB bottom side and reach the U23 pin 3. After measure the circuit hole with meter and confirm that circuit hole was causing the break line. Using a thin-wire and insert it into the circuit hole and then solder both side.
Finally this LCD TV can search the Tv channel and the AV mode can hear the sound. This lcd tv back to normal now!
Conclusion: The circuit hole can be break line, it was because of this circuit line loading heavier electricity (12V & 5V) and resulting in heated completely.
2. How to repair LCD TV Auto Change Channel Problem
Model : Hisense TLM26V68 LCD TV
Chassis: MST721DU
Symptom: LCD TV with auto change channel problem
The complaint of this Television was TV channel will automatically change.During initial observation, the television sound and display were normal. The problem only occurs while watching television programs. First suspect was the remote control or the push button front panel controls. Removed the remote control batteries the problem still remains. Disconnected the CN8 connector (control panel pcb board of the tv) still with the same problem.
Have tried to replace the crystal of main chip, but the problem remain the same. After that, checked the supply voltage to main chip, 3.3V_MST line was getting 3.7V instead of 3.3 volt. So suspect the U2 3.3V SMD voltage regulator IC have problem. After replaced the U2 IC, the TV was back to normal!
Conclusion: Even this article a bit short, but it is helpful to us. We know why the lcd tv can be auto change channel during initial observation now. This method can apply to other tv like Plasma Tv too. So you can use this method to troubleshooting lcd or plasma tv mainboard and find out the culprit!
Model: Hisense TLM2233 LCD TV
Chassis: MST6
Symptom: When in TV mode, the screen shows NO SIGNAL. Try using the AV signal input, got display but no sound.
Power on the Tv, screen display NO SIGNAL and it is showing the snow only. The whole Tv control on/off and other function normal. Try to search the TV channel and can’t find any TV signal! Changed to AV mode, the screen displays present perfectly but no sound. Even adjust the sound volume to maximum also not change.
Check the TV tuner 5V ok but the 33V missing. Check their tuning boost feedback circuit 12V got 0V! Found the service manual and check their audio section was using the same 12V line too. So both symptom of this lcd tv was causing by this 12V line became 0V.
So trace this 12V line on the mainboard and found this 12V line was supply from power supply secondary side and go through U23 (IRF7314) and reach to Tuner and audio section. This U23 function as a switching control and it can on or off the voltage output. After that measuring Q8 base pin for 0.6V normal, U23 pin 1 got 5V input and pin 7 & 8 output normal 5V. Again measuring Q12 base pin for 0.6V ok, then U23 pin3 no 12V input. After that measuring CN16 pin 5, pin6 got normal 12V supply.
Apparently the problem is in between 12V supply (CN16 pin 5 & 6) through U23 pin 3! Using multimeter ohm range, measure in between the CN16 pin 5 through U23 pin3, the meter reading it about 50+ ohm! If normal value it should be 0 or very low ohm. And this line ohm values sometimes can go to 100~300Kohm too! So the circuit line can get unstable ohm values, that’s mean the circuit was intermittently break line. Check the printed circuit board and found the line have circuit hole across PCB bottom side and reach the U23 pin 3. After measure the circuit hole with meter and confirm that circuit hole was causing the break line. Using a thin-wire and insert it into the circuit hole and then solder both side.
Finally this LCD TV can search the Tv channel and the AV mode can hear the sound. This lcd tv back to normal now!
Conclusion: The circuit hole can be break line, it was because of this circuit line loading heavier electricity (12V & 5V) and resulting in heated completely.
2. How to repair LCD TV Auto Change Channel Problem
Model : Hisense TLM26V68 LCD TV
Chassis: MST721DU
Symptom: LCD TV with auto change channel problem
The complaint of this Television was TV channel will automatically change.During initial observation, the television sound and display were normal. The problem only occurs while watching television programs. First suspect was the remote control or the push button front panel controls. Removed the remote control batteries the problem still remains. Disconnected the CN8 connector (control panel pcb board of the tv) still with the same problem.
Have tried to replace the crystal of main chip, but the problem remain the same. After that, checked the supply voltage to main chip, 3.3V_MST line was getting 3.7V instead of 3.3 volt. So suspect the U2 3.3V SMD voltage regulator IC have problem. After replaced the U2 IC, the TV was back to normal!
Conclusion: Even this article a bit short, but it is helpful to us. We know why the lcd tv can be auto change channel during initial observation now. This method can apply to other tv like Plasma Tv too. So you can use this method to troubleshooting lcd or plasma tv mainboard and find out the culprit!
3. How to Repair LCD TV with Symptom No Display but Blue Screen and Vertical White Bars
Brand: Hisense TLM-3233D LCD TV
Chassis: MST9
Symptom: No Display but Blue Screen with Two Vertical White Bars
When power on this lcd tv, the screen show no display but blue screen with two vertical white bars. The two vertical white bars will flash but no any content inside. The LCD TV can hear the sound and remote control to change channel properly. Try other video signals input like AV and PC also same results. Even try to call out the OSD menu also same problem too.
Since the LCD TV cannot show the OSD menu and the TV got sound and change channel properly, so that the mainboard is normal. After observation this lcd tv, found that the problem could be in the T-CON board or LCD panel.
Check LVDS and FPC cables, they are show as normal, then check the T-CON board voltages. All voltages in T-CON board are ok, so that i will suspect the T-CON board mainchip (N39) or their memory chip (N31) defective. I got the junk T-CON board with same part number, but their DC-DC chip was burnt. So the mainchip and memory IC can be use.
t-con board memory IC circuit
t-con board 24LC128 eeprom location
Because of the N39 (CM2681) have many pins and the memory IC N31 (24LC128) only have 8 pins, so that I choose to replace the N31 first. After replace the N31, I try to power on the TV, and it was show display perfectly!
Since this N31 is a memory IC, does that mean IC itself damage or just the firmware corrupt and caused this problem happen? To find out this answer, I use my programmer to copy the working memory IC firmware and write it into the original memory IC. Do you guess what has happen? Yes, the LCD TV working perfectly too! So the problem solved and it was causing by the firmware corrupted.
Conclusion:
The T-CON board memory chip or their firmware corrupt also can cause the screen problem. So that we need to save their firmware and must prepare some junk boards of T-con board, mainboard and inverter board for future use.
4. How to Repair LCD TV No Display, No Backlight But Sound ok
Model: Hisense TLM-55V88GP LCD TV
Chassis: MST6M68FQ-LF-S1
Symptom: When power on the tv, the screen no display and no backlight. But the sound is normal.
After power on the Tv, it is no display and their back light also not work. But the sound is working properly. I can hear the Tv different channel sound after changed the Tv channel.
This lcd tv was using the CMO VIT70077.00 Ver.3 inverter board. This inverter board using the OZ964SN IC as their inverter board controller. When checking the OZ964SN pin 5 (VDDA, voltage supply pin), its 5V supply is missing. After refer to the OZ964SN datasheet and actual inverter PCB board design, found out their 5V was using 24V (inverter voltage supply) line through Q4 to control like a switch to send to U2 (78M05D). After that the U2 will generate 5V and send to U1 (OZ964SN) inverter IC pin5.
The Q4 pin E (Emitter) has voltage input, but the pin C (Collector) no any voltage output to U2. The Q4 pin B (Base) was connected to Q1, that’s mean the Q4 was control by the Q1 too. Check the inverter board connector CN1, the BL-ON signal pin has about 3.4V (active high), that’s mean the mainboard was sent out this backlight on signal to inverter board. But the backlight was not working now. So checking the Q1 now, because it is control the Q4 to working or not. Found the Q1 pin B (Base) had connected to a ceramic cap C8 and it was leakage. This C8 ceramic cap is connected to ground and function as a filter cap.
Because of the C8 just function as a filter cap, so try to remove it and give this TV a try. Finally this Tv was brought back to life now. Find a junk inverter board and get the same size and color SMD ceramic cap to replace it. After testing 7 hours, this Hisense TLM-55V88GP LCD TV is working properly.
Conclusion: Because of the C8 leakage and causing the Q4 can’t switch on, so no any voltage input to U2 (78M05D) to generate the 5V for U1 (OZ964SN) VDDA voltage supply pin (pin 5). So that the inverter board not working and causing backlight also not working too. After replaced C8, the TV is ok now.
Extra Information:
Thank you for all the subscriber email me. Even i'm not reply your email one by one, but i read all your email and really appreciate it. I had received some of the subscriber email me regarding this article, here are the questions:
Q1: How do you know that the values of this cap (C8) is equal to that bad one?
A1: Actually the SMD ceramic capacitor (non polarity type) their values are depends on their sizes. You can refer to the picture below:
So when find the same values of ceramic caps in the junk board was depends on their sizes and color too. For more information about SMD ceramic capacitor, you can visit to this Ceramic Capacitor Information page.
Q2: How you found out C8 was leakaged?
A2: When we don't have this inverter board schematice diagram, so we just can do analysis on their PCB circuit board only. Since in between the Q1 through Q4 components are not much, so we can checking the components one by one. The SMD caps and transistor need to remove to confirm that is ok or bad only. So found that C8 was leakaged.
Q3: Which testing tool gave you this answer?
A3: They are many tools can testing the capacitor, for example, Capacitance meter and Analogue multimeter. For me, i'm using the Analogue Multimeter to test it. Removed the C8 ceramic capacitor and using X10K range to measure it. Normally, when measuring the cap, the needle of meter will go to 0 ohm (charge), after that it will drop to infinity (discharge). When the capacitor can do these two steps, so it can say the capacitor is ok*. So when measuring this C8 cap, the meter needle of meter will not back to infinity and stay on the about 10 ohm position there. So confirm that this C8 was leakaged.
Brand: Hisense TLM-3233D LCD TV
Chassis: MST9
Symptom: No Display but Blue Screen with Two Vertical White Bars
When power on this lcd tv, the screen show no display but blue screen with two vertical white bars. The two vertical white bars will flash but no any content inside. The LCD TV can hear the sound and remote control to change channel properly. Try other video signals input like AV and PC also same results. Even try to call out the OSD menu also same problem too.
Since the LCD TV cannot show the OSD menu and the TV got sound and change channel properly, so that the mainboard is normal. After observation this lcd tv, found that the problem could be in the T-CON board or LCD panel.
Check LVDS and FPC cables, they are show as normal, then check the T-CON board voltages. All voltages in T-CON board are ok, so that i will suspect the T-CON board mainchip (N39) or their memory chip (N31) defective. I got the junk T-CON board with same part number, but their DC-DC chip was burnt. So the mainchip and memory IC can be use.
t-con board memory IC circuit
t-con board 24LC128 eeprom location
Because of the N39 (CM2681) have many pins and the memory IC N31 (24LC128) only have 8 pins, so that I choose to replace the N31 first. After replace the N31, I try to power on the TV, and it was show display perfectly!
Since this N31 is a memory IC, does that mean IC itself damage or just the firmware corrupt and caused this problem happen? To find out this answer, I use my programmer to copy the working memory IC firmware and write it into the original memory IC. Do you guess what has happen? Yes, the LCD TV working perfectly too! So the problem solved and it was causing by the firmware corrupted.
Conclusion:
The T-CON board memory chip or their firmware corrupt also can cause the screen problem. So that we need to save their firmware and must prepare some junk boards of T-con board, mainboard and inverter board for future use.
4. How to Repair LCD TV No Display, No Backlight But Sound ok
Model: Hisense TLM-55V88GP LCD TV
Chassis: MST6M68FQ-LF-S1
Symptom: When power on the tv, the screen no display and no backlight. But the sound is normal.
After power on the Tv, it is no display and their back light also not work. But the sound is working properly. I can hear the Tv different channel sound after changed the Tv channel.
This lcd tv was using the CMO VIT70077.00 Ver.3 inverter board. This inverter board using the OZ964SN IC as their inverter board controller. When checking the OZ964SN pin 5 (VDDA, voltage supply pin), its 5V supply is missing. After refer to the OZ964SN datasheet and actual inverter PCB board design, found out their 5V was using 24V (inverter voltage supply) line through Q4 to control like a switch to send to U2 (78M05D). After that the U2 will generate 5V and send to U1 (OZ964SN) inverter IC pin5.
The Q4 pin E (Emitter) has voltage input, but the pin C (Collector) no any voltage output to U2. The Q4 pin B (Base) was connected to Q1, that’s mean the Q4 was control by the Q1 too. Check the inverter board connector CN1, the BL-ON signal pin has about 3.4V (active high), that’s mean the mainboard was sent out this backlight on signal to inverter board. But the backlight was not working now. So checking the Q1 now, because it is control the Q4 to working or not. Found the Q1 pin B (Base) had connected to a ceramic cap C8 and it was leakage. This C8 ceramic cap is connected to ground and function as a filter cap.
Because of the C8 just function as a filter cap, so try to remove it and give this TV a try. Finally this Tv was brought back to life now. Find a junk inverter board and get the same size and color SMD ceramic cap to replace it. After testing 7 hours, this Hisense TLM-55V88GP LCD TV is working properly.
Conclusion: Because of the C8 leakage and causing the Q4 can’t switch on, so no any voltage input to U2 (78M05D) to generate the 5V for U1 (OZ964SN) VDDA voltage supply pin (pin 5). So that the inverter board not working and causing backlight also not working too. After replaced C8, the TV is ok now.
Extra Information:
Thank you for all the subscriber email me. Even i'm not reply your email one by one, but i read all your email and really appreciate it. I had received some of the subscriber email me regarding this article, here are the questions:
Q1: How do you know that the values of this cap (C8) is equal to that bad one?
A1: Actually the SMD ceramic capacitor (non polarity type) their values are depends on their sizes. You can refer to the picture below:
So when find the same values of ceramic caps in the junk board was depends on their sizes and color too. For more information about SMD ceramic capacitor, you can visit to this Ceramic Capacitor Information page.
Q2: How you found out C8 was leakaged?
A2: When we don't have this inverter board schematice diagram, so we just can do analysis on their PCB circuit board only. Since in between the Q1 through Q4 components are not much, so we can checking the components one by one. The SMD caps and transistor need to remove to confirm that is ok or bad only. So found that C8 was leakaged.
Q3: Which testing tool gave you this answer?
A3: They are many tools can testing the capacitor, for example, Capacitance meter and Analogue multimeter. For me, i'm using the Analogue Multimeter to test it. Removed the C8 ceramic capacitor and using X10K range to measure it. Normally, when measuring the cap, the needle of meter will go to 0 ohm (charge), after that it will drop to infinity (discharge). When the capacitor can do these two steps, so it can say the capacitor is ok*. So when measuring this C8 cap, the meter needle of meter will not back to infinity and stay on the about 10 ohm position there. So confirm that this C8 was leakaged.
5. How to Repair LCD TV Backlight Shurdown Randomly
Model: Hisense TLM4777 LCD TV
Chassis: GM1501 + FLI2300
Symptom: Tv Screen Came In with Tv Logo then No Display, Or Their Backlight Shutdown Randomly.
The customer brings in this TV and complaint that this TV screen will blank after the TV logo came out. But the sound is normal and you can control to change TV channel. This TV is using the Samsung LTA460WS-L03 LCD Panel. Where this LCD Module comes with the inverter board and the part number is: KLS-460BLWSA and B Rev0.1.
After using the PSU self test method and found that this LCD TV was the inverter board defective. This inverter was divided into two boards, one is A board (Master) and another one is B board (Slave). After checking most of the components in the both A & B boards, still can’t found any damage or leakage components. Because of this Tv backlight system just shutdown randomly only, so it is hard to troubleshoot it.
After searching internet regarding this inverter board repairing information and found that it has a common fault about their ceramic caps. These ceramic caps will sensitive with the environment temperature or through their temperature changed their values will change too. So it will cause the protection system made a wrong decision to protect inverter board, even they are no any over voltage or over current occurs in the board or lamps.
The correct method to repair this inverter board is changing all these ceramic caps to 2200P ceramic caps. These caps are location at: C120, C180, C280, C380 & C480. Same as the picture below:
After changed all these ceramic caps and burnt in test about 7 hours, their backlight system still working good. Finally this LCD TV randomly shutdown backlight problem solved!
Notes:
This KLS-460BLWSA Rev0.0 & Rev 0.1 inverter board has another common fault too. For example:
1) Symptom: The TV backlight blink once then backlight system shutdown.
Cure: Replace their T320 & T412 (both part numbers are: BL009 593) HV transformer. Because of their ferrite core were cracked.
2) Symptom: No Display. Because the TV backlight not work.
Cure: Check the Q101SMD transistor. Maybe it is burn or open.
Conclusion:
The hardest symptom on repairing LCD TV is problem on “Randomly”! Because all the components are in ‘good’ condition, so we can’t measure the components with the multimeter or analogue meter only. Some we need some other extra repairing information to help us to troubleshooting the TV.
6. After One Hour LCD TV Display Abnormal
Model: Hisense TLM-4236P LCD TV
Symptom: After an Hour, the TV Display Abnormal in all video inputs
Power on the TV, after about an hour, TV screen will show above photo symptom. Even try different video signals input like TV, AV and HDMI also same problem. So what will cause this TV display problem and how to troubleshoot it?
Regarding the photo symptom, it is looks like the Main board, LVDS cable, T-con board or the LCD Panel defective. Before that, checking all the PSU board outputs voltages are normal and stable. After that cleaning the LVDS cable contact pins with rubble eraser also no help.
When the TV screen problem appears, try to call out the OSD Menu, the OSD Menu can show perfectly in the screen. That’s mean their T-con board and LCD Panel is ok. So the problem was in their Main board!
Checking all the Main board LDO and DC-DC circuits, their voltage outputs are normal and stable. For more details on how to troubleshoot the TV Main board, please refer to V4.0 LCD LED TV Repair Tips ebook. When the screen problem appears, checking the U12 DDR-RAM their Vcc voltage input has stable 2.5V. Also check the U41 Vcc inputs also normal and stable. Suddenly touch the U41 heat sink and feel that extremely hot! When use a plastic rod to pressing U41, the TV screen is back to normal! Even pressing the U12 DDR-RAM, the TV screen also back to normal too. When pressing other components, they are nothing happen or change on it. Just U41 and U12 when pressing it, the TV screen problem gone! So suspect the both of these components are dry join and causing the TV screen problem. Especially the U41, when it’s dry join it will causing their loading heavily and the IC power consumption will increase and generate more heat on the heat sink there.
After re-solder U41 and U12 both IC, testing this TV about 7 hours also no problem. Finally this TV screen problem solved!
7. LED TV Randomly Can’t Power On, Randomly Power Shutdown and Randomly No Display
Model: Hisense LED40K16X3D, LED40K11P, LED40K16P, LED42T39AK, LED42K100, LED42K200, LED42K300, LED42H310, LED46K01P, LED46T39AK, LED37K01, LED37K11, LED37K16、LED50K660X3D, LED50EC660X3D, LED55T36GP, TLM37E29, TLM37V68, TLM37V88P, TLM40V66PK, TLM40V68P, TLM40V68PK, TLM40V69P, TLM42V67PK, TLM42V68PK, TLM42V86PK, TLM42P69GP, TLM42E58P…
Related PSU board: (RSAG7.820.4162) 4162, 5024, 2289, 1673, 1185, 1901& etc.
Symptom:
The TV randomly can’t power on TV, or randomly power shutdown, or randomly no display, or when the TV long time in standby mode, it can’t use the remote controller to control power on TV. But power off the TV and then power on TV back, the remote controller can control the TV now.
Cause:
All these symptom are causing by the PFC voltage output drop below 370V, typically when occur the above symptoms their PFC output voltage is about 340V~ 360V or below 370V. What will cause the PFC output voltage drop? Actually they are many reasons, but in this case, it is because of their PFC IC pin-1 VFB (Voltage Feedback) sampling circuit line corresponding component/s leakage. Especially their voltage divider resistors are a common fault of this strange problem in TV power supply (PSU). It is because of these divider resistors leakages and it is causing by the red glue (Seal Glo) under these SMD resistor. For example the RSAG.7.820.1673 PSU board (normally call it as 1673 board), their divider resistors R823, R824 & R825 are inside the PFC section as photos below:
Repair/Solution:
Removed these divider resistors, cleaning their PCB board red glue and also the red glue attached on the bottom of SMD resistor. After clean all these red glue from the above divider resistors (R823, R824 & R825) and solder it back to their appropriate location. Finally this type of strange problems in LED TV was solved. Remember, not all the above PSU board their divider resistor is same these R823~R825, may be different part number of PSU board will vary. But their reason is same, is because of the PFC IC pin Voltage Feedback sampling circuit line component/s was leakage and caused these strange problem occur.
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Model: Hisense TLM4777 LCD TV
Chassis: GM1501 + FLI2300
Symptom: Tv Screen Came In with Tv Logo then No Display, Or Their Backlight Shutdown Randomly.
The customer brings in this TV and complaint that this TV screen will blank after the TV logo came out. But the sound is normal and you can control to change TV channel. This TV is using the Samsung LTA460WS-L03 LCD Panel. Where this LCD Module comes with the inverter board and the part number is: KLS-460BLWSA and B Rev0.1.
After using the PSU self test method and found that this LCD TV was the inverter board defective. This inverter was divided into two boards, one is A board (Master) and another one is B board (Slave). After checking most of the components in the both A & B boards, still can’t found any damage or leakage components. Because of this Tv backlight system just shutdown randomly only, so it is hard to troubleshoot it.
After searching internet regarding this inverter board repairing information and found that it has a common fault about their ceramic caps. These ceramic caps will sensitive with the environment temperature or through their temperature changed their values will change too. So it will cause the protection system made a wrong decision to protect inverter board, even they are no any over voltage or over current occurs in the board or lamps.
The correct method to repair this inverter board is changing all these ceramic caps to 2200P ceramic caps. These caps are location at: C120, C180, C280, C380 & C480. Same as the picture below:
After changed all these ceramic caps and burnt in test about 7 hours, their backlight system still working good. Finally this LCD TV randomly shutdown backlight problem solved!
Notes:
This KLS-460BLWSA Rev0.0 & Rev 0.1 inverter board has another common fault too. For example:
1) Symptom: The TV backlight blink once then backlight system shutdown.
Cure: Replace their T320 & T412 (both part numbers are: BL009 593) HV transformer. Because of their ferrite core were cracked.
2) Symptom: No Display. Because the TV backlight not work.
Cure: Check the Q101SMD transistor. Maybe it is burn or open.
Conclusion:
The hardest symptom on repairing LCD TV is problem on “Randomly”! Because all the components are in ‘good’ condition, so we can’t measure the components with the multimeter or analogue meter only. Some we need some other extra repairing information to help us to troubleshooting the TV.
6. After One Hour LCD TV Display Abnormal
Model: Hisense TLM-4236P LCD TV
Symptom: After an Hour, the TV Display Abnormal in all video inputs
Power on the TV, after about an hour, TV screen will show above photo symptom. Even try different video signals input like TV, AV and HDMI also same problem. So what will cause this TV display problem and how to troubleshoot it?
Regarding the photo symptom, it is looks like the Main board, LVDS cable, T-con board or the LCD Panel defective. Before that, checking all the PSU board outputs voltages are normal and stable. After that cleaning the LVDS cable contact pins with rubble eraser also no help.
When the TV screen problem appears, try to call out the OSD Menu, the OSD Menu can show perfectly in the screen. That’s mean their T-con board and LCD Panel is ok. So the problem was in their Main board!
Checking all the Main board LDO and DC-DC circuits, their voltage outputs are normal and stable. For more details on how to troubleshoot the TV Main board, please refer to V4.0 LCD LED TV Repair Tips ebook. When the screen problem appears, checking the U12 DDR-RAM their Vcc voltage input has stable 2.5V. Also check the U41 Vcc inputs also normal and stable. Suddenly touch the U41 heat sink and feel that extremely hot! When use a plastic rod to pressing U41, the TV screen is back to normal! Even pressing the U12 DDR-RAM, the TV screen also back to normal too. When pressing other components, they are nothing happen or change on it. Just U41 and U12 when pressing it, the TV screen problem gone! So suspect the both of these components are dry join and causing the TV screen problem. Especially the U41, when it’s dry join it will causing their loading heavily and the IC power consumption will increase and generate more heat on the heat sink there.
After re-solder U41 and U12 both IC, testing this TV about 7 hours also no problem. Finally this TV screen problem solved!
7. LED TV Randomly Can’t Power On, Randomly Power Shutdown and Randomly No Display
Model: Hisense LED40K16X3D, LED40K11P, LED40K16P, LED42T39AK, LED42K100, LED42K200, LED42K300, LED42H310, LED46K01P, LED46T39AK, LED37K01, LED37K11, LED37K16、LED50K660X3D, LED50EC660X3D, LED55T36GP, TLM37E29, TLM37V68, TLM37V88P, TLM40V66PK, TLM40V68P, TLM40V68PK, TLM40V69P, TLM42V67PK, TLM42V68PK, TLM42V86PK, TLM42P69GP, TLM42E58P…
Related PSU board: (RSAG7.820.4162) 4162, 5024, 2289, 1673, 1185, 1901& etc.
Symptom:
The TV randomly can’t power on TV, or randomly power shutdown, or randomly no display, or when the TV long time in standby mode, it can’t use the remote controller to control power on TV. But power off the TV and then power on TV back, the remote controller can control the TV now.
Cause:
All these symptom are causing by the PFC voltage output drop below 370V, typically when occur the above symptoms their PFC output voltage is about 340V~ 360V or below 370V. What will cause the PFC output voltage drop? Actually they are many reasons, but in this case, it is because of their PFC IC pin-1 VFB (Voltage Feedback) sampling circuit line corresponding component/s leakage. Especially their voltage divider resistors are a common fault of this strange problem in TV power supply (PSU). It is because of these divider resistors leakages and it is causing by the red glue (Seal Glo) under these SMD resistor. For example the RSAG.7.820.1673 PSU board (normally call it as 1673 board), their divider resistors R823, R824 & R825 are inside the PFC section as photos below:
Repair/Solution:
Removed these divider resistors, cleaning their PCB board red glue and also the red glue attached on the bottom of SMD resistor. After clean all these red glue from the above divider resistors (R823, R824 & R825) and solder it back to their appropriate location. Finally this type of strange problems in LED TV was solved. Remember, not all the above PSU board their divider resistor is same these R823~R825, may be different part number of PSU board will vary. But their reason is same, is because of the PFC IC pin Voltage Feedback sampling circuit line component/s was leakage and caused these strange problem occur.
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