LG 27GL63T-B completely dead

[Sventy]

Hi! I have two of these monitors, last night i turned my pc off. Today, when turning on the pc, one of the monitors is dead aswell.

This happened to me just today as well. Crazy.

[Dannyx]

Wow....surprised how many of these are failing ! Even more ironic is that the replacement board I got for my colleague less than a year ago ALSO failed just a couple of days ago AGAIN ! Big pen!s-shaped stain on the face of LG here...

[hukkaja]

An unprofessionally shot clip i uploaded to imgur (4.8mb, 19sec):
https://*******

[Pandor]

Mine just broke down to.
Got home from work, turned on my PC and.. nothing. luckily this is my secondary monitor.
Just for reference, mnfr date: 04/2020
This thread will come in handy. haven't opened mine yet, but this was the first search result.

[Pandor]

Re: LG 27GL63T-B completely dead

Another success story:

....

I replaced my IC401 with part named MP2149GJ-P (the original part has been retired) and the monitor started working. YAY!

The MP2149GJ-P is also rated 2A (original part was rated 1A). Not sure if this is total amperage or per channel. But if someone still has burned IC401, I suggest giving the MP2149GJ-P a try, it might be better version with more overhead.

Thanks also to everyone who contributed.

MP2149GJ is indeed the equivalent to MP9148GJ, same specs, so its 1Amp output with 100 mΩ high-side ON resistance. I'll be repacing with a MP2122AGJ which is rated for 2A, and a ON resistance of 80 mΩ. So less power dissipation and less voltage drop across the switch.

https://www.monolithicpower.com/en/mp2122a.html

[markismus]

I've blown c451 of the board while I replaced IC402 (|AGCK). Can't find it anywhere.
Would anyone be able to tell me the capacitance? Thanks!

[nva]

Hello, mine also dead. Has been working for over 2 years. It never left my desk. And then one day... no sign of life when hitting the power button.
Took the pcb out of the monitor and tried to understand what is going on, but my knowledge is just not enough to test it and find the problem.
All, I know (and have measured with multi meter) is that the power adapter works as it sends the 19v into the power jack that is on the pcb.

I have a hard time reading the pcb and its traces and since there is now sheet available I don't know where to look.

BUT: I am having fun learning about electronics, circuits and components..

[Pandor]

So what should the actual voltage outputs be for IC400, IC 401, IC 402?
I just replaced IC401 with MP2122AGJ, but IC402 seems dead also... 19v input, no output...

[markismus]

So what should the actual voltage outputs be for IC400, IC 401, IC 402?
I just replaced IC401 with MP2122AGJ, but IC402 seems dead also... 19v input, no output...

Doesn't mean it's dead. Could also mean that it doesn't receive a trigger voltage on the relevant pins.
I've posted all datasheets a few posts back. On it are the input range voltages and the output response to the control pins.

[Pandor]

Doesn't mean it's dead. Could also mean that it doesn't receive a trigger voltage on the relevant pins.
I've posted all datasheets a few posts back. On it are the input range voltages and the output response to the control pins.

there's no standby, so yeah, that rail might only became active when powered on. IC402's EN pin is low when connecting power to the board.

Resistance to ground after L407 on the output seems pretty low at 47ohm, so my current guess is there's a short on that output rail (that might have caused the original 1A rated regulator to die).
in diode mode, I'm getting 0.0422v ground to L407 coil.... maybe a dying cap after the coil... not sure.

there is 19v going to IC402 and IC400.
There is 5v going to IC401

IC 402 EN is low, no output
IC 400 output is 3.3v
IC 401 output is 0.3v on left side (L408), 1.16v on right side (L407) -- (this should be 2.5v and 1.2v?)

[markismus]

These were the values that I measured at my defunct board.
(IC402 = AGC = MP2315, IC400 = AQT = MP2315S: 1 = AAM, 2 = IN, 3 = SW, 4 = GRD, 5 = BST, 6 = EN/SYNC, 7 = VCC, 8 = FB)
(IC401 = AKX = MP9148: 1 = FB2, 2 = EN2, 3 = SW2, 4 = EN1, 5 = GND, 6 = SW1, 7 = IN, 8 =FB1 )

So my IC400 also has 3.3V on output.
My 401 has 0.08V and 1.2V on resp. SW1 and SW2. Since EN1 = 1.7V and EN2 = 0.3V, I would expect them to behave differently. I'll check later when I have more time. The IN = 2.15V instead of the expected 5V, so that could also explain the odd behaviour.
my 402 has 0.8V on EN/SYNC, so it should not output anything on SW. However, it also doesn't have 5V on VCC, so it doesn't work anyway, right?

Pandor Looks like we at least have the same problem situation.

I've bought a 20k crystal oscillator. I'll replace that one first, before checking the buck converters again.

[Pandor]

My expected output voltages were based on the LG 27gl850 service manual posted in this thread. I assume the voltages should match... as this model doesn't differ that much.

[markismus]

As the numbering is different from ours, I used the datasheets. However, I am interested now wat the analogue to ic705 would be.

[Pandor]

As the numbering is different from ours, I used the datasheets. However, I am interested now wat the analogue to ic705 would be.

I believe that would be the AKX. The ic numbering might be different, but the general power rails seem to match. The AKX is the only dual output, so hence my assumption.

For me the AKX seems to start at 2v output briefly, but goes down to 0.08v on SW1. So it could be going into safe mode/protect. The weird thing is that the SW1 side does not seem to have a short on my board, but the SW2 side has a rather low resistance to ground. If anyone can confirm it should be 2.5v, i might try injecting that after the coil.

markismus the abcence of 5v input at the AKX is worrying though. In my case the 5v is present.

[Pandor]

I believe that would be the AKX. The ic numbering might be different, but the general power rails seem to match. The AKX is the only dual output, so hence my assumption.

For me the AKX seems to start at 2v output briefly, but goes down to 0.08v on SW1. So it could be going into safe mode/protect. The weird thing is that the SW1 side does not seem to have a short on my board, but the SW2 side has a rather low resistance to ground. If anyone can confirm it should be 2.5v, i might try injecting that after the coil.

markismus the abcence of 5v input at the AKX is worrying though. In my case the 5v is present.

the powerrails actually match up in the service manual. Only IC401 seems to be IC403 in the schematics. This also explains why IC 402 would be low, as that seems to generate the 12v for the panel.

So i seem to be missing 1.8v, or rather it drops out at power up. I'll dig some more on that rail.

I'll just inject 1.8v into that rail and see what gets hot, and the power draw. Something on that rail seems to bring it down as soon as it powers up. Resistance on the unpowered rail seems fine though.

I just hope its not the CPU, as the 1.8v seems to split into VDD_DRAM and VDDIO and those just go through a capacitor cluster, and then into the cpu..

[Pandor]

...
My 401 has 0.08V and 1.2V on resp. SW1 and SW2. Since EN1 = 1.7V and EN2 = 0.3V, I would expect them to behave differently. I'll check later when I have more time. The IN = 2.15V instead of the expected 5V, so that could also explain the odd behavior.
my 402 has 0.8V on EN/SYNC, so it should not output anything on SW. However, it also doesn't have 5V on VCC, so it doesn't work anyway, right?

Pandor Looks like we at least have the same problem situation.

I've bought a 20k crystal oscillator. I'll replace that one first, before checking the buck converters again.

Those readings seem to be way off. after replacing 401, i get:
IN=5v
EN1 and EN2=3.3v
SW2=1.16v (close enough)

But SW1 goes straight down to 0.08v. so in my case, something is overloading the SW1 side, making it go into protection mode.
I have a bad fooling the CPU is taking the rail down..

[markismus]

Pandor Resoldered AKX with stereomicroscope and now it measures

PIN	1	2	3	4	5	6	7	8
Reference	FB2	EN2	SW2	EN1	GND	SW1	IN	FB1
Voltage	0.6	3.3	1.17	3.3	0	1.8	5	0.6

So that seems good. Also replaced the crystal oscillator with a new 12.000 Hz one.

AQT changed slightly to

PIN	1	2	3	4	5	6	7	8
Reference	AAM	IN	SW	GND	BST	EN	VCC	FB
Voltage	0.3	19	3.3	0	8.3	2.5	5.0	0.8

AGC is now

PIN	1	2	3	4	5	6	7	8
Reference	AAM	IN	SW	GND	BST	EN	VCC	FB
Voltage	0	18	0	0	~0	~0	~0	~0

[markismus]

No joy, though.

[Aertop]

Hello,

I have the same error, the monitor has just "died".

Symtomp: The monitor has stop working suddently, it does not show any light neither work any button, completely dead.

The power supply works fine.


Inspecting the PCB board with a thermal camera the IC401 shows a higher temperature than the rest of the board.

My readings for the IC401 are:

Pin 1	Pin 2	Pin 3	Pin 4	Pin 5	Pin 6	Pin 7	Pin 8
0,7V	3,3V	1,2V	3,3V	Ground 0V	5V	5V	1,6V

Does those readings OK, or should i look for another component?

Edit -> The IC400 just burned, i will replace that, does anyone know the part number?


Thank you!

[Pandor]

markismus posted some great pictures with correct IC labels and datasheets, one page back.