Thursday, July 4, 2024

LG 49-inch LED television model 49LH549V has no picture but sound was okay.

 I received a phone call from a client who wanted his television checked by a technician.

The client told me he suspected backlight failure, so I proceeded to the site armed with all equipment for any scenario.

I arrived at his place hassle-free since he gave directions, the name of the court plus the house number very well.

On arrival, I was shown the television which was still mounted. I unmounted it and placed it on the table.

I placed the television with the back cover up, applied the power, and noted the backlights were ON.

With that, I realized the issue was not backlights like the owner had hinted and therefore had to do more detective work to diagnose the problem.

I also noted the screen has a blueish background. This means that the TV is working well but missing the data.

In this case, the main suspects are TCON, LVDS cables, COF, and motherboard.

I decided to begin checking the TCON, the best place to begin is by testing if the TCON is getting the 12Volts from the motherboard.

The best place to test this voltage is across the fuse as shown below.

Kindly be sure to test this voltage on both sides of the fuse, this will help you to know if the fuse is open or not.

I tested and found the voltage on both ends of this fuse, this means the 12 voltage from the motherboard is present and stable.

Next, I checked the VGL voltage and got zero, this voltage is usually negative. Tested across the two coils and one has 12 volts and the other one has near zero volts again.

I suspected the TCON was faulty and before making the conclusion I decided to remove the LVDS cables one by one.

After removing this side, I re-tested the voltages again and now I was able to get VGL voltage at -5Volts.

I turned the television on the screen side and this is what I saw.

This made me conclude that the issue is on the small circuits connected to the panel as you can see here below.

Since they are two and identical I decided to test the few components there for shorts since the only thing that can bring down voltage is short on the power line.

When testing my meter set to continuity, I found these two capacitors buzz indicating shorts. I removed them one by one and still the buzz remain, this means the short is elsewhere. I re-soldered both and continued with my troubleshooting.

I noted this other capacitor at the far end which also tested shorted with my meter.

I removed it out of the circuit and the short was gone completely.

I applied the power to the television and the television came up beautifully.

Thank you guys

See you in the next class


learn how to fix electronic gadgets here

 

1 comment:

  1. Thanks a lot for sharing. Am wondering if you replaced the culprit cap or you let the machine do without it.

    ReplyDelete