LG LCD TV Backlight blinking problem troubleshooting - LG 60LB7100 Intermittent Backlights

Backlights Blink
• Backlights go OFF.

SMPS Trouble LED blinks 3 times then only 2 times.
Note: This panel was a Refurbished panel from parts.

Panel P/N: CRD31515701
TV ran for 4 days, 24 hours a day until symptom showed up.

The backlights would begin to blink. Usually 4 to 6 times then they would shut off completely.
• SMPS LED was blinking 2 times indicating DC-to-DC converter problem.
• However, when watching the SMPS trouble LED while the backlights were blinking, it blinked 3 times once or twice then it went to 2 times after the backlights went off. 3 times indicating Open LEDs.
• While Backlights were blinking: Reading the test points EL50-EL54 EL62-EL67 on the SMPS for backlight grounding signals, all but two test points were reading approximately 4V. But two of them were reading 0V, (EL55 and EL64). Backlight Power was 70V.
• While Backlights were off: Reading the test points EL50-EL54 EL62-EL67 on the SMPS for backlight grounding signals, all but two test points were reading approximately 7V.
But two of them were read 0V (EL55 d EL64). Backlight Power was 56V.
• Note: In this model there are only 6 backlight drivers. So two test points are tied together per/driver.

Reading the test points EL50-EL54 EL62-EL67 on the SMPS for backlight grounding signals, all but two test points were reading approximately 6V. But two of them were reading 0V, (EL55 and EL64).
Note: In this model there are only 6 backlight drivers. So two test points are tied together per/driver.
Example: EL62 and EL54 are tied together, EL55, EL64 are tied together, etc
Note: When the Backlights are “off”, the reading are 2V on good LED bars and “0V” on the defective bar.

LED (LD701) would blink 3 times while backlights were blinking and 2 times after the backlights turned off.

Note: LED (LD701) blinking 3 times indicates an open backlight LED feedback line.
Check the Test points EL50-EL54 EL62-EL67 for “20V” volts. This would indicate an Open LED driver.
Using a 100 ohm resistor, one end to ground, touch the other end to the Test Point pin that has “20V”. If the backlight comes on, the panel is good, SMPS is bad.

After disassembling the panel, we found that the connector to the bottom LED Bar was intermittent. The connector is attached by simply pressing it down onto the connector. The Red wire (B+) to the bar was intermittent making contact with the connections on the LED Bar. On all “A” bars, LED B+ arrives on the (-) marked pin on the connector. On all “B” bars, LED B+ arrives on the (+) marked pin.

This connector is inserted by laying it over the connector on the board and pressing down to press it into place.  For those unable to do panel disassembly, panel replacement is necessary.

The best repair method for this would be to remove the wires and solder them directly to the LED bar.

Avoid solder bridges. Cut the crimped connector off the wire first.
For permanent fix, you should do this to all “outside” connectors on the right and the left side of the LED Bars.
Note: You may need to un-tape the wire harness to allow for slack. Be sure to re-tape after repair.

Examine each LED to make sure they have not become un-bonded. “Do not life by the LED lens”. Over time, this could cause overheating.
if they have, press down on either side of the LED for about 60 seconds to rebond.  Do not press down on LED.

How to disassemble BBKV3N,V3H,V5N,V5H pocket TV

All operations must be with strict anti-static measures. Operators must wear anti-static gloves or wrist ring; electric screwdriver must be grounded effectively and articles, such as nippers must be removed static before using Use cuspidal forceps to take out the LOCK button

Insert the forceps into the lock hole and then prize up one corner of the glass.

Use a slice with thickness about 0.1mm to in sert into the gap of the glass prized up and then peel off glue of the glass slowly to tale out the glass. Pay attention not to damage touch button FPC.

After peeling off glue of the glass, use nails to take out the glass.

Insert the 4 special slice clasp instruments into the relevant position of the 4 clasps.

Use the special hook tool, shown in the picture,to remove the middle casing.

Remove FPC flat cable clasp and then use forceps to take out FPC flat cable.

Use electric screwdriver or “+”-shaped screwdriver to take out 2 screws of main board.

Use iron to weld to separate the batter and buzzer lead wire on main board.

Take out main board components Take out battery components.

Take out the stainless steel cover board on rear side of display screen.

Take out display screen components from the direction shown in the picture.

Lenovo laptop disassembling - Lenovo ideapad 710S – How to remove the battery pack – How to remove base cover

To verify a symptom, follow the steps below:
1. Turn off the computer.
2. Connect the AC adapter.
3. Make sure that power is supplied when you turn on the computer.
4. Turn off the computer.
5. Disconnect the AC adapter.
6. Make sure that the battery pack supplies power when you turn on the computer.
If you suspect a power problem, see the appropriate power supply checkout:
“Checking the AC adapter”
“Checking operational charging”
Checking the AC adapter
You are here because the computer fails only when the AC adapter is used.
If the power-on indicator does not turn on, check the power cord of the AC adapter for correct continuity and installation.
To check the AC adapter, follow the steps below:
1. Unplug the AC adapter cable from the computer.
2. Measure the output voltage at the plug of the AC adapter cable. See the following figure:

Note: Output voltage for the AC adapter pin No. 2 may differ from the one you are servicing.
3. If the voltage is not correct, replace the AC adapter.
4. If the voltage is acceptable, do the following:
Replace the system board.
Note: Noise from the AC adapter does not always indicate a defect.
Checking operational charging
To check whether the battery charges properly during operation, use a discharged battery pack or a battery pack that has less than 50% of the total power remaining when installed in the computer.

Perform operational charging. If the battery status indicator or icon is not lit, remove the battery pack and let it return to room temperature. Reinstall the battery pack. If the charge indicator or icon is still off, replace the battery pack. If the charge indicator is still not lit, replace the system board.

Restore of factory default
The Lenovo ideapad 710S-13ISK computer comes with pre-installed OneKey Recovery System.In order to save application files and the initial backed up files of the system, the hard disk in a Lenovo computer includes a hidden partition when it is shipped. If you need to restore the system to the point of your first boot up, just enter Lenovo OneKey Recovery System and run System Recovery.

Disassembling procedure 

Base cover

Remove the rubber. Remove the screws 1. Then remove the base cover 2.

Battery pack

Disconnect the battery connector 1 and remove the screws 2.

Lift up and remove the battery.

PCI Express Mini Card for wireless LAN

Disconnect the two wireless LAN cables (black, white) 1, and then remove the screw 2.

Remove the card in the direction shown by arrow 3

In step 1, unplug the jacks by using the removal tool antenna RF connector (P/N: 08K7159), or pick up the connectors with your fingers and gently unplug them in the direction shown by the arrows.

Notes: The wireless LAN card has 2 cables in step 1. The wireless LAN card in some models might have 3 cables in step 1.