AOC Q3279VWF, no power

[Sraros]

Hello,

I have this monitor that doesn't power up. I hear a tiny clicking sound which indicates a short. I run a quick visual test and found on the mainboard right before the VGA and HDMI outputs these burnt components as attached in the pictures.
What could cause such a thing and should I go for a repair?

[lotas]

Re: AOC Q3279VWF, no power

This could happen if the hdmi cable was connected "hot" or due to lightning.

[Sraros]

Re: AOC Q3279VWF, no power

This could happen if the hdmi cable was connected "hot" or due to lightning.

Maybe lightning more possible since both VGA and HDMI have burnt components right before output?
If I desolder these should I expect to power up or maybe the monitor is completely damaged?
The power board seems intact all fuses are good

[lotas]

Re: AOC Q3279VWF, no power

Maybe lightning more possible since both VGA and HDMI have burnt components right before output?
If I desolder these should I expect to power up or maybe the monitor is completely damaged?
The power board seems intact all fuses are good

In such cases, the scaler (microcontroller) usually burns out.

[R_J]

Re: AOC Q3279VWF, no power

The parts on the hdmi line are for protection on the data lines, they can be removed for testing, the data lines should be straight through under the udfn-10 (DFN2510-10)esd protector. Like mentioned above, there is likely a lot more that is bad.
If you do have it working a possible replacement part would be a PESD1LVDS by Nexperia

[Sraros]

Re: AOC Q3279VWF, no power

Hello, returning on this thread.
I finally received a replacement mainboard.
The monitor now opens, meaning there’s standby voltage.
Also if i hit the power button it turns on but there’s nothing on the screen. With flashlight test there’s nothing showing.
When I connect the HDMI cable it also opens automatically but there’s no sound from windows (like there’s a new device connected)
The backlights work for sure.
Does this mean I also need an inverter board?

[Sraros]

Re: AOC Q3279VWF, no power

Attached a photo of the T-con.
The fuse F301 is ok but the little smd zener diode Z301 is shorted.
I went through the inverter boards and the rest of T-CON and didnt find any other short.

[lotas]

Re: AOC Q3279VWF, no power

Z301 is not a zener diode, it is a pass-through, interference suppression capacitor, there should be no short circuit between 1.2 and 4 pin.

[Sraros]

Re: AOC Q3279VWF, no power

Z301 is not a zener diode, it is a pass-through, interference suppression capacitor, there should be no short circuit between 1.2 and 4 pin.

Ok.
1-2 shorted
3-4 shorted
Not between them though

[Sraros]

Re: AOC Q3279VWF, no power

The last test I did was to remove the ribbon cables one by one to the inverter boards. When I removed the left ribbon nothing changed. When I removed the right ribbon there was white on the right when the logo of AOC should flash on screen.

[Sraros]

Re: AOC Q3279VWF, no power

Coming back quite some time later on this. So I picked up from where I left this monitor.
I cleaned the ribbon cables from the T-con to the panel boards and I have image now but is way off! The logo is displayed like in photo attached, split. The image is terrible and flickering noise sound from the boards. Any suggestions?

[Sraros]

Re: AOC Q3279VWF, no power

VIN: 12.75V
VGH: 29.7V
VGL: -7.3V
VCOM: 6.3V
VDD: going up to 3.25V then dropping to 0 on and on.
Voltages remain the same with or without the ribbon cables connected

Is it safe assumption it is the T-con board at fault if the VDD comes and goes with and without the ribbon cables connected on the panel boards?

[Sraros]

Re: AOC Q3279VWF, no power

I changed the T-con board with another good working one from a same monitor with broken panel but nothing. Same results