MSI Optix G241 - Lines

[mchen96]

Hi,

I have an MSI Optix G241 monitor that basically displays gibberish (see below). For context, I am a well-equipped hobbyist that dabbles in electronics and has repaired more than a few things, but I am not a professional nor have I formally studied electronics.



The monitor has two main PCBs. The first one is located under a metal shielding and contains the main power supply, backlight supply, HDMI inputs, and connectors for the power button, menu controls, and power led. The second board is connected to the panel via permanently attached flex cables; it plays the role of a TCON board.



While I cannot be 100% sure, I am fairly certain that the first board is fine; all voltage rails measure sensible levels (12v, 3.3v, and a backlight voltage). A visual inspection revealed no damage on either board. I believe the damage is centered on the Tcon board.

I've attached closed-up images of the board below.



There is a slight buzzing sound coming from capacitors C38 and C157, which correspond to the VDDG (VGH) filter capacitors.

I initially suspected that one of the power rails generated in the TCON board was off given the buzzing. The IC that generates the LCD voltage rails is IC4, which is "helpfully" marked "X03H 2562". Searching that led me nowhere, but I eventually determined it to be a BM8110MUW (or something pin compatible to it, at any rate). I took the time to trace the power section of the TCON board. While it was ultimately unhelpful to me, I'm including it below as others might find it useful for unrelated problems (refer to the datasheet for half of the endpoints in the page below).



All voltage rails are measuring reasonable voltages (or at least, within the bounds of the limits in the datasheet). The power IC's fault pin remains high (datasheet states it is pulled low on power fault). I'm guessing the buzzing I am hearing is due to the charge pump and is probably normal, but inaudible once the case back is installed (it is admittedly somewhat faint).

For reference:

Vin (TP3 test point) = 12.2 V
V3.3 = 3.28 V
VDDA = 13.91 V
HVDDA = 6.28 V
VDDG = 28V (with +- 0.5V ripple)
VGL = -7.82V
V12 = 1.09V

While I haven't traced the source of these rails, these also look fine

VCOMR = 6.0 V
VCOML = 6.0 V

Anyone has any ideas or guesses?

[lotas]

Check the resistance of the test points (CKA..., CKB...) relative to GND, it should not be low or short-circuited.

[mchen96]

None of the clock signals (GCK1-GIP to GCK4-GIP) are shorted , they all measure about 400 k to ground.

I believe I've narrowed down the issue to the level shifter (IC2), a Novatek NT50413S.

The signals before it are good (GSP and GCK), as shown below. I have a nice 60 hz signal on GSP with the screen connected to a camera's hdmi out, and the GCK frequency (67.47 KHz) seems about right for 1 pulse per row (not that I've counted them).




I'll admit I have no idea what the clock signals after the level shifter (GCK1-GIP to GCK4-GIP) should look like, but I can tell that what I got ain't it.

Yellow trace is trigger on GSP before the level shifter, purple trace is GSP-GIP after the level shifter.



Yellow trace is trigger on GSP before the level shifter, purple trace is GCK4-GIP after the level shifter. Other clocks show a similar pattern



I'll try to doublecheck the level shifter's inputs. If I cant find anything, I'll probably reflow it just to see if it changes something.

[Diah]

remove the LVDS from the LCD T-CON boards and test it as stand alone with 12V-

[mchen96]

remove the LVDS from the LCD T-CON boards and test it as stand alone with 12V-

Screen appears black (with backlight on) when turned on without the LVDS cable connected.

Signals after the level shifter still seem off. Signals before it seem fine.

(Yellow: GSP signal before level shifter used as trigger, Purple: GCK1-GIP after level shifter).



PS: I'm rather new to the forum, I just noticed that there is a "Computer Displays" Section. I'd be grateful if a moderator could move the thread to the correct section.