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Louie
Louie, Technician
Category: TV
Satisfied Customers: 2557
Experience:  25+ yrs. experience in the field and 5+ yrs. online, down to component level.
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Just checking out some post on an LG 55LM7600I have the same issue wit

Customer Question

just checking out some post on an LG 55LM7600
I have the same issue with mine. I repaled the main / power board but just checking to see if there were any other suggestion
Submitted: 1 year ago.
Category: TV
Expert:  Aric replied 1 year ago.
Hello, Can you please describe in detail exactly what the problem with your TV is? What's it doing, or not doing? I have no way of seeing the post that brought you here. Please elaborate on the problem you're having.
Customer: replied 1 year ago.
Hello, I have an LG55LM7600. We believe there was a power surge while we were away, although we have the TV on a surge protector and battery backup. Our neighbor told us the re was a lightning strike close enough that but shook the house. The red LED is on when the set is off. When the set is turned on with the remote or with the hard button the LED blinks. It's as if it blink once, waits and then blinks three times, waits a cole of seconds and just repeats the same process. I have replaced the power board but it has not changed anything it still does the same one blink- three blink repeatedly. The TV was purchased in September 2012.
Customer: replied 1 year ago.
It's been 45 minutes and I have not heard anything I don't know if this site is working
Expert:  TV Tech1 replied 1 year ago.
The site is back online. AFTER replacing the power board, do you see the TV screen stay pitch black after turning it on, or does it at least light up to a gray level? The power supply may be turning on, but the LED panel has to light up gray before the TV will turn on the picture and sound.
Customer: replied 1 year ago.
The screen stays pitch black
Expert:  TV Tech1 replied 1 year ago.
Read this picture --
Customer: replied 1 year ago.
If I understand your message, I should use a digItal volt meter to check for 3.3 volts on terminal 4 and 12 ( counting from the left) when the power switch is pressed. If I see 3.3 volts when the on button pressed then the power board is not at fault
Customer: replied 1 year ago.
I'm on the eastern time zone so I will check it in the morning
Expert:  TV Tech1 replied 1 year ago.
Yes, I would do that, BUT..I ALWAYS check for both ON and OFF voltages on EACH pin. WHY? Because some OFF voltages are 3.3 Vdc and ON is 0 Vdc. You really want to make sure both can switch states when you press the power button, and especially see HOW the DRV-ON pin behaves .If it never switches states your screen's backlight can never turn on and light up. If it switches states, THEN goes OFF...then the backlight inverter is reading a shorted LED lamp in the panel. That's what we need to find out. And since you replaced BOTH boards...it's highly likely.The key is this - The PWR-ON turns on the rest of the power supply, thus powering up the inverter drive. Then the DRV-on line applies power to the LEDs, lighting up the screen. But it checks for shorts, and shuts off if there is. So the behavior of the Drv-on line is important, and it waits about 5 seconds after Pwr-on is initiated before it turns on.Check PWR-on, make sure it also Powers off, then go to the Drv-on line and monitor it for a good 5 seconds from when you press the power button.
Customer: replied 1 year ago.
Using 1 as to top terminal and 12 as the bottom terminal you asked me to check. With the power off there was no voltage on 4 which you indicate is the DRV on. When the power was switched on, voltage switched to 8.66 volts cd and would cycle until the power LED turned off then the voltage would slowly diminish. I suspect the capacitor were discharging. When the power was off, I had a negative 3.4 DRV on terminals 7 and 8. When the power is on all the voltages on the terminals fluxuate. Terminal 11 has higher voltage than the rest is cycles at 21.55 volts. Something I had not noticed before there is a red LED on the board has begu. To flash five times repeatedly when the power was switched off or on. This was not occurring before.
Customer: replied 1 year ago.
Auto correct changed some words. The voltage was 8.65 volts DC. And 3.4 volts DC
Customer: replied 1 year ago.
FYI I have not replaced the other board. I only replaced the power board
Expert:  TV Tech1 replied 1 year ago.
Hmm, those numbers and the terminal numbers are odd to me. See the DOT by the Power-on pin? That is pin 1 on all connectors. Power-on is pin 1.Pin 2 is the 14 Volts UNDER pin 1.Odd number pins is the TOP row...EVEN number pins is Below the Top.Power-on is pin 1Drv-on is pin 18 (bottom row, 4th from left)The red led indicates LIFE on the board, but does not give a fail code. LG does not use fail codes.
Customer: replied 1 year ago.
OK Thanks. I didn't understand correctly. is it OK to remove the plug going into this socket to get the reading or do I need to find a back probe
Expert:  TV Tech1 replied 1 year ago.
Leave the plug installed, those test voltages come from the main board and turn on the power supply and the power supply's LED inverter. Keep in mind that LED inverter isn't making the TV screen GLOW so we need to see what the DRV-On line is doing. If you don't have a real sharp pointy voltmeter probe, you may have to unscrew the power supply board, get underneath it to test that Drv-on pin. I prefer probing the plug if I can.
Customer: replied 1 year ago.
Sorry, im not understanding. in order for me to check the power on the white receiver plug you showed in the photo I can only reach the upper row of pins. in order for me to reach the bottom row where the dvr pin is located I either have to remove the board from the set or remove the connector that is going into the receiver plug
Expert:  TV Tech1 replied 1 year ago.
Don't remove the connector, you need that signal coming from the main board. If necessary put a couple pieces of paper as insulation on the board, making sure the TOP of the board does not contact the TV frame or display panel. That's ground, and those heatsinks are usually connected to Hot side of power. Isolate the board so you can get under the board. That, or simply solder a thin wire to the pin on bottom and screw that board back on.
Customer: replied 1 year ago.
I was able to use a straight pin and there is no voltage on the DRV when the power was turned on. Sorry it took so long but I could not get back to you there was something going on with the site
Expert:  TV Tech1 replied 1 year ago.
Well that DRV-ON comes from the TV's main board. If it's dead your panel cannot light up. Have you replaced that part? If not, check the board, find out which number your TV uses (read the details after you access one of the board pages, it will give you the model number's suffix found on that model number sticker on the rear cover. Match it, and write down the part number. Then google it for a supply of that specific board. http://www.shopjimmy.com/catalogsearch/result/index/?cat=56&q=55LM7600
Expert:  TV Tech1 replied 1 year ago.
Why did the moderator close this? Did you read and run or are you confused from my last post?
Customer: replied 1 year ago.
I grew frustrated with the site. I couldn't post responses. The customer help center was laughable. I took the tv to a shop. Thanks for your help
Expert:  TV Tech1 replied 1 year ago.
Ok, thanks for the info.