U2312HM will not turn on

[habibalex]

I have 2 Dell U2312HM that won't turn on anymore. Both are completely unresponsive. The power went out a few months ago and took 1 monitor out, yesterday the power went out again and took the other out.

I have taken 1 monitor apart and replaced some components on the signal board:

• I301 (5V to 3.3V regulator but had 0V out)
• all the electrolytic caps on the Signal board.

When I supply external DC power supply 5V to I301, I get a constant 3.3V out. When I check the 5V pin of the Power Board when the Signal Board is disconnected I also get 5V. However with both of the signal board and power board connected through the wire cables I see a fluctuation in the 5V up and down to about 1V.

I am not really sure where to go from here since I don't know much about power electronics. Does anyone have a schematic for the power board L0281-2M? I have taken a look at some other posts but I haven't been able to find anything to proceed further.

[R_J]

Re: U2312HM will not turn on

I would replace C807, this is the startup/vcc cap. It could be weak and not charging to the full vcc to keep the primary circuit running.

[habibalex]

Re: U2312HM will not turn on

Thanks RJ. I tried connecting the signal board from bad monitor 1 to the good power board of bad monitor 2 and when I started it up the display had a 2 images side by side and the colors / resolution were messed up. I think something else is wrong w/ the monitor 1 signal board beyond that bad voltage regulator also.
I'll try replacing that vcc cap.

I was able to replace the bad 3.3V voltage regulator I301 on bad monitor #2 and it is working as expected now. https://youtu.be/tQVnBMDsqio

[krsta]

Re: U2312HM will not turn on

While i was trying to repair this power board (L0281-2M) i realised fuse F802 was dead and moved my hand and piece of wire has fallen on I801 and it poped killing him and D806. Does anyone know what ic is that and the walue of diode?

[lotas]

Re: U2312HM will not turn on

See which scheme is more suitable.

[krsta]

Re: U2312HM will not turn on

Thx for schematics.

[FluxCap123]

Re: U2312HM will not turn on

I also have a U2312HM that I am trying to repair (won't turn on - most of the time). I found these videos of someone troubleshooting one:
https://www.youtube.com/watch?v=U6V1sjWMgeM and
https://www.youtube.com/watch?v=ACbNq9dTwBo.
They are in Portuguese and you can turn on captions and get YouTube to translate (sort of).

In the first video he replaces one of the ICs to get it working. In the second video he replaces a fuse. In the comments for the first video there is a link to a schematic that I think the video author made: https://onedrive.live.com/?authkey=%...212829&o=OneUp

Hope you get your monitor working.

[honda22]

Re: U2312HM will not turn on

I have this monitor and it won't turn on. No blue led, nothing. I get it to an electronic guy, checked the power board and also the Voltage Regulators and told me they are all good.
So I start searching for replacing the logic board.
Mine's version is L0144-1 48.7M701.011 but after some search on Ali I found only L0144-2M 48.7M701.02M version.

Could anyone tell me if this will work?

[honda22]

Re: U2312HM will not turn on

Any suggestion?

[lotas]

Re: U2312HM will not turn on

Any suggestion?

The fact is that every motherboard has spi flash and eeprom and they contain firmware and settings for their panel (matrix) and if it does not match, it may not show anything or show it but with distortions.

[stankolima]

Check and replace F802 (5v rail) mine has 100 ohm resistence.