LG 27GL63T-B completely dead

[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]

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]

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]

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]

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]

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...

[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..

[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!

[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

[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.

[hukkaja]

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

[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...

[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.

[hukkaja]

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. Lifetime of the monitor: 2 years, 7 months. Utterly disappointed. I have minimal electric experience. I ordered the new IC401 chip to try out if that solves the issue. How would one approach desoldering, soldering the new chip? It is 2mm long, has 4 pins on each side. Seems really precise work. The chip has IAKXM written on it that i hope is the culprit. Will add some images soon. All i can say that i truly like these monitors, brilliant. 144hz, 27" and 1080p. Perfect for my eyes and usage case. I am an all-rounder pc user.

[voveo]

Hi all! Can someone measure the resistance of the L407 and L408 power phases on the working board? thanks in advance, I have the following power supply on the phase resistance board: L407 340 ohm L408 39 ohm

[C:\]

Re: LG 27GL63T-B completely dead

My LG 27gl650f also died suddenly. I don't have a thermal imaging camera, but by touching the various components with my finger, I noticed that the IC600 gets hot after a few seconds. Have any of you had problems with the IC600 and managed to solve it? In the meantime I will order mp3378r and try to replace it

LG uses different IC numbers across different models on the pcb even if the circuits or in this case buck converters are laid out the same using the same parts. What is the IC number on top of the chip and what is it a part of/goes to it? If it's another buck converter it likely has the same failure issue as our AGC and AKX IC's, common issue in this design across all LG models containing it it seems. Should be able to look up the ic and find its outputs then troubleshoot similarly. Probably another short if its hot. Can also check if the LC coils are shorted coming off of it if buck.

[JoeDocked]

Re: LG 27GL63T-B completely dead

My LG 27gl650f also died suddenly. I don't have a thermal imaging camera, but by touching the various components with my finger, I noticed that the IC600 gets hot after a few seconds. Have any of you had problems with the IC600 and managed to solve it? In the meantime I will order mp3378r and try to replace it

[markismus]

Re: LG 27GL63T-B completely dead

I've used my magnifier and the IC codes are:

IC101:
SD642AO or SD642A0
TI 69A680I G4 of TI 69A68OI G4

IC201:
FT24C32A
9eHBAC

IC202:
BE1941
25Q80CSIG or 25080CSIG

IC500:
TPA6138
98TG4
CISZ

IC600:
MPS1928
MP3378R
K4871538X

[markismus]

Re: LG 27GL63T-B completely dead

You got power going to the board, but nothing happens? Check the crystal. If the crystal isn't working nothing else is either. Check the SPI flash and pull the data sheet. Check if you can update the firmware. Maybe this thing has a TTL port hook up to it and see what happens there. Look at the board and check the little buck converter(s) maybe one is shorted to GND.

I've added 2 Hi-res photo's. (How do you take a photograph from a PCB without the glare?)



The |AKX buck regulator generates 2.0V falling down to 0.89V and continuing on the L409 coil. It's too hot to touch.
The |AGC step down converter generates 0V on the L410 coil.
The |AQT step down converter generates 3.33V on the L405 coil.

I've added the datasheet of these three. It seems that only the |AQT is working as expected. I've ordered the other two from AliExpress. Nor the L410 coil nor any but connection 4 (GRD) of |AGCK showed a short to GRD.


The crystal X200 is tagged SC12.000 A1930. My multimeter only goes to 10MHz, so I only see the 50Hz of the power net. I assume it's 12MHz. Can't find a way to check it yet. Is there sense in just swapping it out with another and see what happens?

P200 could be the TTL port. Not quite sure how to hook it up yet, though.

Any idea what part could be the SPI flash? IC600 has MPS1928 on it, which seems to be a voltage regulator. IC101 is quite unreadable. IC201 and IC202, too.

[C:\]

Re: LG 27GL63T-B completely dead

Thank you very much to all for this information, I was able to repair a 27GN750 using the information and service manuals posted here - it shares very similar components and it's IC401 was also dead, output pins 3 and 6 both shorted to ground. Replaced with the recommend 2A replacement here and it powered right on. Now repairing my 27GL63T with a shorted IC401 and no output on IC 402 although receiving 19v. My C508 near the audio Jack is also shorted, haven't tested further or put a jack in yet but will replace my IC401 and 402 and see what I get next. Does anyone have a good model IC for 402? I'm otherwise looking for a similar IACGK online and will help for the best.