LG 65UH7650 (4k UHD)

[ngsss]

I am new, so hopefully I don't sound like an idiot. I am looking for some help diagnosing this tv. I don't have picture but have a standby light on the front of tv. When I turn the power button on the back light does not come on. I cant seem to figure out where the standby is on the power supply to test volts. Attached is a picture of what im dealing with and the volts I am reading for each one. First Set of numbers is when tv OFF second set is when its ON.

TV WAS IN A POWER SURGE WHEN THIS OCCURED


OFF / ON
0v / 2.2v
0v / 6.4v
2v / 55.9v
0v / -5.2
8.3 to 9.5v / 13.3v (first set of numbers keeps fluctuation up and down)
8.3 to 9.3v /13.28v (first set of numbers keeps fluctuation up and down)
0v / -5.4v
0v /3.49v
0v / -4.5v

[budm]

Re: LG 65UH7650 (4k UHD)

https://www.badcaps.net/forum/attach...9&d=1536624905
1) That connector has 18 pins, those pins you can see from the top side of the board are ODD number pins, the white dot indicate pin 1, so the next pin will be 3, 5, 7, 9, .....
The EVEN number pins you cannot see from the top side of the board so you need to use skinny tip probe to probe from the wire entrance side of that female connector.
2) Each pin has pin name so to get help from us you MUST put down the pin name and follow by the DC Voltage reading of each pin for us to easily see what each pin has when TV is OFF and when power switch is activated. As you can see: pin 1 is 'GND', pin 3 is 'PWR_ON', pin 5 is 'GND, pin 7 is 13.2V, ..............

[ngsss]

Re: LG 65UH7650 (4k UHD)

Thank you for the info! Here is what I have for volts with the tv plugged in not turned on. (I have a standby light showing on tv)


PIN#s ---DC volts reading
17/18 --- 0v / .1v
15/16----0v / .1v
13/14----2v / 0v
11/12----0v / 0v
9/10-----8.3 to 9.5v / 8.3 to 9.5v
7/8------8.3 to 9.3v /8.3 to 9.5v
5/6------0v / 8.3 to 9.5v
3/4------0v /0v
1/2------0v / 0v

[ngsss]

Re: LG 65UH7650 (4k UHD)

Vsync/s[n
gnd/sclk
drv_on/p-dim1
gnd/gnd
13.2v/13.2v
13.2v/13.2v
gnd/13.2v
pwr_on/p-dim2
gnd/gnd

[budm]

Re: LG 65UH7650 (4k UHD)

1) Is this your board, look at the barcode of shopjimmy and your board. LG EAY64210802 Power Supply / LED Driver Board. http://www.shopjimmy.com/lg-eay64210...ver-board.htm#
2) Remove the cable between power supply and the main board then check to see if the 13.2V will come up to 13.2V or not.

[ngsss]

Re: LG 65UH7650 (4k UHD)

budm:
Yes, that is the power supply I have.
I removed the cable and it measured 9.8v-10v, in all (5) of the 13.2v ports

[R_J]

Re: LG 65UH7650 (4k UHD)

That 13.2 might read low if the power supply is not turned on, there is no PWR_ON signal from the main board, I suspect the PWR_ON should be around 3-5 volts when the power button is pressed.
The fault could be with the main board
If you disconnect P201 from the main baord, you could try applying +3 volts to (J13 PWR_ON) , that should turn on the power supply if it is ok.

[budm]

Re: LG 65UH7650 (4k UHD)

That 13.2 might read low if the power supply is not turned on, there is no PWR_ON signal from the main board, I suspect the PWR_ON should be around 3-5 volts when the power button is pressed.
The fault could be with the main board

I believe you are correct, If I am correct, this LG may have lower Voltage when it is in standby and goes to full 13V when the power supply board receives the PS-ON to turn on the PFC and the rest of the power supply.
So far the PS-ON (PWR_ON) and some other control signal are not present.

[ngsss]

Re: LG 65UH7650 (4k UHD)

I believe you are correct, If I am correct, this LG may have lower Voltage when it is in standby and goes to full 13V when the power supply board receives the PS-ON to turn on the PFC and the rest of the power supply.
So far the PS-ON (PWR_ON) and some other control signal are not present.

So you both think the main board could be the issue? Is that what would be recommended to get?

[ngsss]

Re: LG 65UH7650 (4k UHD)

When the tv is “on” the pwr_on reads 3.2v, all the 13.2 read 13.2v.

[budm]

Re: LG 65UH7650 (4k UHD)

OK, I did not pay attention regarding the Voltages in post 3 with the TV OFF, so PS-ON is good, the power supply does come up to 13V when PS-ON is present so the main board is not completely dead.
So how about the DRV_ON and the Dim control signals when TV is turned on?

[ngsss]

Re: LG 65UH7650 (4k UHD)

Drv_on reads 56.5v, dim1 and dim2 reads 3.3v.

[budm]

Re: LG 65UH7650 (4k UHD)

Drv_on reads 56.5v, dim1 and dim2 reads 3.3v.

That must be an error, no way DRV_ON can be that high, 56.5V! Please retest.
Are you sure it is not 56.5mV?

[ngsss]

Re: LG 65UH7650 (4k UHD)

That must be an error, no way DRV_ON can be that high, 56.5V! Please retest.
Are you sure it is not 56.5mV?

budm, Yes, sorry you are correct. It is mV.

[budm]

Re: LG 65UH7650 (4k UHD)

budm, Yes, sorry you are correct. It is mV.

That means the main board is not sending the DRV_ON (BL-ON) ti turn on the backlights circuits.
You can try force on the backlight by simulating the DRV_ON command signal using external 3V supply (use 2 AA batteries connected in series feeding to DRV_ON pin through 100 Ohms resistor) but you have to disconnect the DRV_ON wire going back to the main board first.

[ngsss]

Re: LG 65UH7650 (4k UHD)

That means the main board is not sending the DRV_ON (BL-ON) ti turn on the backlights circuits.
You can try force on the backlight by simulating the DRV_ON command signal using external 3V supply (use 2 AA batteries connected in series feeding to DRV_ON pin through 100 Ohms resistor) but you have to disconnect the DRV_ON wire going back to the main board first.

OK, just made a series and the back lights did turn on.

[budm]

Re: LG 65UH7650 (4k UHD)

OK, So now you do have lights source, then if everything else are OK with the main board, T-CON board, LCD panel then you should see pictures, if not, then you more problem then just missing DRV_ON signal.

[budwich]

Re: LG 65UH7650 (4k UHD)

I know you have done lots of "good things" to determine source of the problem. Before going further, can you try the "easy test" (if you haven't already)... disconnect, one at time, the cables going from the tcon to the panel and see if it changes the results any. It might point you in a different direction. Not normally a failure as a result of a power surge BUT there are components that may not like that event and can be somewhat isolated with this test.

[ngsss]

Re: LG 65UH7650 (4k UHD)

OK, there is no picture present. When I disconnected the tcon one at a time. The right side flashed real bright like the tv was on, while the left side did nothing.

[budwich]

Re: LG 65UH7650 (4k UHD)

sorry but I don't understand your observations / report. What cable was off and what was the display doing with respect to that side. Of course, you need to have something input or at least put up a menu perhaps to see something on the screen.
Anyways, please restate your observations a bit better.