Faults LCD

LCD TVs. COMMON FAULTS AND REPAIRS

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LCD TVs are todays most trend, and they are invading the electronic entertainment market, ad seems to go further. Here are some faultfinding guidelines; with you can understand the fault to your TV to an extent, provided you must have knowledge in electronics.  Sometimes, you may even repair your LCD TV too. 

Let us discuss first with its power supply section, which is more venerable to faults.

Symptom:  The LED at the front panel of the TV do not light up, even connecting the power cord and switch the TV ON.  The unit appears to be Dead condition

There is a relay connected to power supply.  It should work [when it works, you can hear a click sound can be heard after the TV is switched ON]. Listen to this click sound.

Check the status of cable connections inside the TV for any loose. Check fuses fitted with power supply regulator board and any other. Check the input voltage at the SMPS [Switched Mode Power Supply] otherwise called as power regulator board. If all these are found OK, and still the set refuses to switch ON the Relay, and no power indicator LED lights up at its front panel, make sure that the main board is faulty.  There is no repair to it by replacing components.  Replacing it is the only repair work.

Come to other possibilities.

• Is power LED at its front panel is on and the lamp [backlight] is OFF.  If NO, check the connections of the power cable and all other cables connected to the power regulator board. If YES, does the power standby DC voltage [5VDC] is present or not.  If NO, change the main power assembly.

• If [5VDC] is present, check the main DV voltages [13VDC].  If it is not there, check the associated capacitors, especially check the ceramic capacitors if any connected to this voltage. If there is no fault with any of the associated components, and still there is no 13VDC, the power regulator board is faulty, and should be replaced.

• If this 13VDC is present and there is no main 120VDC present, check all the associated capacitors.  If they are also found normal. Power supply regulator board is faulty, and should be replaced.

• If there is 120VDC is present and no 3.3VDC check the regulator IC on the main board, either for open or for loose soldering points at its terminals. Suspect the main boar assembly too in this case.

• Check the voltages at CODEC, 3.3VDC, 8VDC & 9VDC.  If these voltages are there or not there, and the set wont switch ON, make sure that the main board is faulty.  In rare cases, a well-experienced service technician may set it right.  In 90% cases, replacement of 
• the main board is the only remedy.

If 1.2VDC core voltage, and VCC33, VCC12, VCC25 are present, appear at FRC board and still set refuses to switch ON, the fault is not with picture circuits. Then you have to check the LCD panel.

Here is a Test Cases Of LCD LEDs TV From Different Sources. 

Samsung LE32R73BD: No picture and no OSD menu. Backlight ok.
Model/s: Samsung LE32R73BD LCD TV
Symptom: No picture and no OSD menu. Backlight ok.
Cure/Solutions: Reflow LVDS socket on screen driver PCB and mainboard PCB.

SAMSUNG LE32R74BD: TV dead. Pulsating noise from PSU and LED light flashes.
Model/s: Samsung LE32R74BD LCD TV
Symptom: TV dead. Pulsating noise from PSU and LED light flashes.
Cure/Solutions: Check shottky diode DM854 (MBRF1545CT) in PSU for short circuit.

BUSH LCD32TV005HD: After TV on few seconds, then the TV off again.
Model/s: BUSH LCD32TV005HD APH000 Chassis BEKO LM LCD TV
Symptom: Picture appears for a few seconds after switch on, after that the TV switches off again.
Cure/Solutions: Check C2042 and C2044 (both 680uf/35v) in PSU for capacity loss.

BUSH LCD32TV005HD: No Picture and no back light. Front controls react and remote control does not.
Model/s: BUSH LCD32TV005HD APH000 Chassis BEKO LM LCD TV
Symptom: No Picture and no backlight. The front controls was working but remote control does not
Cure/Solutions: Replace IR receiver (short circuit).

JVC LT32DX7B: No functions after lightning strike
Model/s: JVC LT32DX7B LCD TV
Symptom: No functions after lightning strike.
Cure/Solutions: The primary voltage 300v is present. But secondary voltage output was only 21 volt. Replace standby transformer T9201.

Sharp LC32P55E: Red LED appears for a seconds, relay clicks then dead.
Model/s: Sharp LC32P55E LCD TV
Symptom: Red LED appears for a seconds, relay clicks then dead.
Cure/Solutions: The resistor R751 blown. Replaced IC704 & R751.

Sharp LC32P55E: Dead after start-up. Bang-noise head before
Model/s: Sharp LC32P55E LCD TV
Symptom: Dead after start-up. Bang-noise head before.
Cure/Solutions: Replace R751 (0.1R/2W), IC704, D762, D725 and C725 (470pF/3K) in PSU.

Philips Chassis BJ3.0E LA: Switches off for a second or two intermittently
Model/s: Philips Chassis BJ3.0E LA LCD TV
Symptom: Switches off for a second or two intermittently. Relay clicks and standby LED remains green. Switches off intermittently with green LED on, no sound or no picture.
Cure/Solutions: Please check the 27MHz KDS quartz crystal (SSB, item 1H00). If all yellow marked crystals bearing with a "5E", "5J" or "5K" batch number direct replaced it. Also replaced all the silver marked crystals bearing with a "6D" batch number.

LG 37LE2R: No start-up
Model/s: LG 37LE2R Chassis LP61A LCD TV
Symptom: No start-up.
Cure/Solutions: Replace SMD regulator TL431 (U130) in PSU.

LG 27LC2R: No Backlight
Model/s: LG 27LC2R Chassis LP61A LCD TV
Symptom: No backlight
Cure/Solutions: Check the SMD fuse F1 on inverter board for open circuit.

Samsung LE27T51B: Dark frame with color stripes
Model/s: Samsung LE27T51B LCD TV
Symptom: Dark frame with color stripes.
Cure/Solutions: It looks like the unstable voltage problem. Check and replace UP4 (L1117DG) on T-CON board.

LG 32LE2RZJ: Remote control no functions at all
Model/s: LG 32LE2RZJ Chassis LP61A LCD TV
Symptom: Remote control doesnt function at all.
Cure/Solutions: Replace SMD capacitor at output of IR receiver.

ACER AL2671W: Dead
Model/s: ACER AL2671W LCD TV
Symptom: Dead.
Cure/Solutions: Replace power supply IC (TNY264PN) and resistor R60 (10R/0.33W, NFR type).

ACER AL2671W: No start-up. LED is orange
Model/s: ACER AL2671W LCD TV
Symptom: No start-up. LED is orange.
Cure/Solutions: When C380 unsuccessfully replaced. Standby PSU functions and standby 5v present. The voltage appears at pin PSON in the PSU after switch on but PSU does not start. Actually they are three 330K SMD resistors in series in the PSU which supply voltage for DLA001. Check if resistors are high resistive.

Bush IDLCD26TV05HD: No backlight and no picture. Sound ok and can be intermittently
Model/s: Bush IDLCD26TV05HD Chassis L9 (Beko) LCD TV
Symptom: No backlight and no picture. Sound ok and can be intermittently.
Cure/Solutions: Replace C512, C513 (both 1000uF/35v) and C519 (220uF/35v) in PSU. Also a 1000uf/16v capacitor on the signals board on the far right-hand side, near the top.



SONY

KDL40U2000: No start-up, red LED flashes 3 times
Model/s: SONY KDL40U2000 with SE1 Chassis LCD TV
Symptom: No start-up, red LED flashes 3 times.
Cure/Solutions: TV has slow start-up before this symptom occurred. When check standby 5v ok and PSU is heat sensitive. Check and replace the C6055 (47uf/25v) in G2 supply it will solve the problem.

BUSH LCD32TV022HD: Intermittently no start-up or dead after a few hours
Model/s: BUSH LCD32TV022HD with 17MB15 Chassis LCD TV
Symptom: Intermittently no start-up or dead after a few hours.
Cure/Solutions: The PSU replaced and EEPROM IC resoldered, but on help. Try to resolder IC220 (SDA5550) and IC224 on main board the TV back to normal.

EVESHAM ALQEM37SX: No start-up, the TV screen lights up, then switches back to standby mode
Model/s: EVESHAM ALQEM37SX with 17MB15 Chassis LCD TV
Symptom: No start-up, the TV screen lights up, then switches back to standby mode.
Cure/Solutions: Please check or direct replace the C877 and C878 on PSU board for open circuits. Sometime these caps will check good, but would breaks down under load.

Grundig GULENAR32HDIP: Stuck in standby mode, LED light is blue color
Model/s: Grundig GULENAR32HDIP with Chassis L9 LCD TV
Symptom: Stuck in standby mode, LED light is blue color.
Cure/Solutions: The blue LED always stays on, even when appliance is on standby mode. Capacitor C931 (1000uF) replaced but appliance is still dead with 12v and 24v ok. Check and replace diode D300 on the right-hand side, on middle-top of the main board.

Samsung LN40A650_A750_LN46A750: Unit tries to start with melody but cycles off and back on
Model/s: Samsung LN40A650A1FXZA,LN46A650A1FXZA,LN40A750R1FXZC,LN46A 750R1FXZA,LN40A750R1FXZA LCD TV
Symptom: Unit tries to start with melody but cycles off and back on
Cure/Solutions: If the unit tries to turn on and makes the startup melody but then immediately shuts off and starts again, unplug the LVDS cable and apply power again. If the set stays on, replace the T-Con board.

Samsung LNT4665FX/XAA lost brightness when you replaced MAIN PCB
Model/s: Samsung LNT4665FX/XAA LCD TV
Symptom: LNT4665FX/XAA lost brightness when you replaced MAIN PCB
Cure/Solutions: Because MAIN PCB BN94-01199E is designed to work with both models LNT4665FX/XAA and LNT4661FX/XAA when you replaced the board is possible to lose the brightness. Go in SERVICE MODE and turn value LVDS BYTE from 8 to 10.


Samsung LNS4051: Dead Backlight Flashes On Then Off
Model/s: Samsung LNS4051DX/XAA LCD TV
Symptom: DEAD BACKLIGHT FLASHES ON THEN OFF
Cure/Solutions: UNIT WOULD FLASH ON THEN OFF AND AUDIO WOULD WORK. YOU COULD SEE VIDEO WITH A FLASHLIGHT. SOMETIMES UNIT WOULD STAY ON AND RUN IF YOU CYCLED ON AND OFF MANY TIMES. FOUND BAD SOLDER CONNECTION ON IP BOARD TI801 ON PRIMARY SIDE. RESOLDERED AND CORRECTED PROBLEM.


Samsung most model: Flickering on the screen intermittently
Model/s: Samsung
LN32B360C5DXZA,LN32B530P7FXZA,LN32B460B2DXZA,LN32B 540P8DXZA,LN32B550K1FXZA,LN37B530P7FXZA,
LN37B550K1FXZA,LN40B550K1FXZA,LN40B530P7FXZA,LN40B 530P7NXZA,LN40B530P7FXZC,LN40B540P8FXZA,
LN46B530P7NXZA,LN46B530P7FXZA,LN46B550K1FXZA,LN46B 540P8FXZA.
Symptom: Flickering on the screen intermittently
When the unit is connected via HDMI to a Scientific Atlanta cable set top box set in by pass mode for resolutions 480p and 720p a flickering will occur.
Cure/Solutions: Change the cable box to a fixed resolution. OR Have the customer install the latest TV firmware which can be located on samsung.com.

PART 2

Samsung: LN32A450_LN32A330: Video will intermittently turn mostly white
Model/s: Samsung LN32A450C1DXZA,LN32A450C1HXZA,LN32A450C3HXZA,LN32A 330J1DXZA,LN32A330J1NXZA LCD TV
Symptom: Video will intermittently turn mostly white

White display with a faint image of OSD (On Screen Display) and video in the background. Video will intermittently turn mostly white with the OSD barely visible in the background. Even a black image or when the panel should not be showing any video, it is white. I found that one of the sub-boards inside the panel, the boards that the ribbon cable from the T-Con connect to, are not seated properly and the larger SMD capacitors on the board are intermittently making contact with the metal frame of the set, effectively creating a short to ground.
This is one of the panels that are mounted upside down, so the stand mounts just below and behind the panel frame. Any slight pressure from the stand can cause the frame to make contact. In many cases, the TV can be slightly flexed to make this issue occur.
You may see besides a T-Con ribbon cable, that the sub-board is not seated properly, and is in fact bowing towards the outer frame.
Pulling the frame out slightly, you can see one of the SMD capacitors that can make connection with the frame.
Cure/Solutions: Adding felt to the affected area will solve the issue.

Samsung most model: Firmware Blinking in Red at the Top of the Screen
Model/s: Samsung LN32B360C5DXZA,LN32B530P7FXZA,LN32B650T1FXZA,LN32B 460B2DXZA,LN32B540P8DXZA,LN32B550K1FXZA,
LN32B640R3FXZA,LN32B457C6HXZA,LN32B450C4HXZA,LN37B 457C6HXZA,LN37B530P7FXZA,LN37B650T1FXZA,
LN37B550K1FXZA,LN40B457C6HXZA,LN40B550K1HXZA,LN40B 500P3FXZA,LN40B550K1FXZA,LN40B650T1FXZA,
LN40B530P7FXZA,LN40B530P7NXZA,LN40B750U1FXZA,LN40B 540P8FXZA,LN40B610A5FXZA,LN40B630N1FXZA,
LN40B640R3FXZA,LN46B650T1FXZA,LN46B530P7NXZA,LN46B 530P7FXZA,LN46B550K1FXZA,LN46B610A5FXZA,
LN46B540P8FXZA,LN46B630N1FXZA,LN46B640R3FXZA,LN46B 750U1FXZA,LN52B550K1HXZA,LN52B610A5FXZA,
LN52B550K1FXZA,LN52B540P8FXZA,LN52B530P7FXZA,LN52B 630N1FXZA,LN52B750U1FXZA,LN55B640R3FXZA,
LN55B650T1FXZA LCD TV.
Symptom: Firmware blinking in Red at the top of the screen.
Cure/Solutions: Problem - After changing the main board, I'm now stuck with the firmware text info blinking in RED print at the top of the screen.
Solution : The unit is stuck in aging mode. To exit, simply hit the menu button on the TV itself.

Samsung LNT4065_LNT5265: With Signal-Blue Screen and Flashing White Short Horizontal Lines
Model/s: LNT4065FX/XAA,LNT4665FX/XAA,LNT5265FX/XAA,LNT4061FX/XAA,LNT4661FX/XAA
Symptom: Blue screen without signal, with signal -blue screen with flashing white short horizontal lines
Cure/Solutions: Refit or replace LVDS cable, check if the cable not strangled by the metal cover and loosen up the screws of the cover.

Samsung LNT3242_3232 : Wont Power On
Model/s: Samsung LNT3242HX/XAA,LNT3232HX/XAA LCD TV
Symptom: Wont power on
Cure/Solutions: TV would not come on. Removed the back and as soon as we did the set came on.
Found glue all on the cables to the smps. Cleaned glue off and cleaned the terminals. Set operates normally.

ACER AL2671W: No start-up. LED is orange
Model: Acer AL2671W LCD TV
Symptom: No start-up. LED is orange.
Cure/Solution: Check C380 (100uf.16v) under heatsink, next to U42 and U61 on signal PCB for capacity loss.

Sony KDL32U2000: No Picture
Model: Sony KDL32U2000 Chassis SE1 LCD TV
Symptom: No Picture
Cure/Solution: Check SMD fuse CP101P on LVDS board. The LVDS board is behind the BDT board.

SONY KDL32S2010E: Switches to standby for a short while, then back again
Model: SONY KDL32S2010E Chassis WAX2 LCD TV
Symptom: Switches to standby for a short while, then back again
Cure/Solution: Replace standby push button on user control, has contact resistance.

Philips 32PF3320/10: "F" is displayed on screen
Model: Philips 32PF3320/10 Chassis LC4.5 EAA LCD TV
Symptom: "F" is displayed on screen
Cure/Solution: TV is in factory mode. To quit the factory mode, press both "VOLUME" "-" keys and "PROGRAM" "-" for 5 seconds simultaneously.

LG 32LC56: Picture divided into several parts. Distorted picture
Model: LG 32LC56 LCD TV
Symptom: Picture divided into several parts. Distorted picture
Cure/Solution: Replace T-CON board (Part Number: 218394).

LG 32LC56ZC: No start-up. Standby LED flashes from red to green
Model: LG 32LC56ZC LCD TV
Symptom: No start-up. Standby LED flashes from red to green
Cure/Solution: Replace C202, C206, C217 and C218 (2200uf/10v all), and C226 (470uf/25v).

GOODMANS GTV26WLCD: Shuts down and LED blinks
Model: GOODMANS GTV26WLCD LCD TV
Symptom: Shuts down and LED blinks

Cure/Solution: Replace C877 and C878 (both 15nf/630V).

Imran Ashraf