Asrock H81M-ITX no 12V

[Epagec]

Hello,

I have this MB that was working correctly
- Asrock H81M-ITX (Micro ITX with Core i5-4460)

I have tried another PCIe Graphic card to check if working and something burnt after 2 minutes...

Now the PCIe port is not working, CPU_FAN and CHA_FAN are not working neither.

PC can start and work with the in CPU integrated GPU, I have tried with antoher PSU but it's not the PSU

Also the 12V monitoring on bios says 'N/A'

I can't see the burnt component and I don't have so much skills on desktop motherboards, the rail doesn't seems to be shorted.

Up to my understanding the problem should be the 12V rail that powers the PCIe and Fans.

I don't have the schematic to check the components on this rail (I will ask for).

Do you have any ideas from where to start ?

Thank you so much for your help !

[stj]

Re: Asrock H81M-ITX no 12V

check the voltages on the pcie connector - maybe the card drew too much current and burned a track or inductor

[Epagec]

Re: Asrock H81M-ITX no 12V

Voltage is very low on pcie connector and fan connectors (0,2v), diode mode to ground is 0.547

[stj]

Re: Asrock H81M-ITX no 12V

diode mode to ground is pointless - you will just see diodes & stuff
can you post a picture near the power connector?

[harp]

Re: Asrock H81M-ITX no 12V

Check all power pin, and write voltage reading and pin number/name
Is graphics card still ok, that that cause burnout? Give picture on another pc?

[Epagec]

Re: Asrock H81M-ITX no 12V

The graphic card is dead, it broke the MB, I have another one known good.
I will test all pins but I can tell that the firsts pins for 12V are 0v
What is strange is that it smells like burnt but I can't find where
I uploaded the picturof power con and pcie

[harp]

Re: Asrock H81M-ITX no 12V

Try sniff near close to pcie, and atx and determine area with burned smell. I see some mosfet, maybe with burnmark/burntrace near atx...
What is resistance pcie 12v rail to ground, can you trace back from where is caming to? (Elec. Cap, coil, ic...)

[Epagec]

I have tried to find Something burnt but nothing is obviously burnt.
There is no short on the rail, I inject 12v from the atx pin and there is no consumption, I don't get the 12v on pcie and fan connector.
I have tried to inject 12v from the pcie port and fan connector and no shorts.
I have no continuity between atx port and pcie and fan port.
I don't have the boardview but I've seen on other models that pcie 12v and Fan connector are directly coming from the psu 12v connector.
I can conclued that there is a broken track between them.
Do you think that I can wire the 12v atx psu to the pcie connector directly ?
Do you see any option out of the broken track ?
For info when I inject 12v from pcie conn I get 12v on cpu_fan conn. But when I inject 12v on chassis fan connector I get 11,5v on cpu_fan and pcie...
Than you !

[harp]

I have no continuity between atx port and pcie and fan port.

You must determine location, find where is broken connection, is it burn surface track, track inside layer, via, 000 resistor, fuse, coil...
Use copper brush, or ball pile of aluminium foil to do it quickly, like

https://www.youtube.com/watch?v=F_Mi-SwZyxY