Burn SMD on MSI Z77A-G45

[TheQuentincc]

Hi, I'm coming here because my second PCIE x16 on my motherboard doesn't work, just below it I can see a burned SMD which could be a resistor or capacitor, I don't know how to check it but when I mesure it with my ohmeter the resistance is above 6M ohm, here a pics to show you :

(below/left the "SFC")
I already try to find a schematics or a board view but I find nothing, so I decided to mesure all SMD thing (with the same size) near the PCI-E slot and I see that the resistance vary with the time (so maybe it was a capacitor specification ?).
I don't know what to do, should I short circuit it? should I use "pencil mod" to decrease the resistance ? should I try to replace it by a similar size capacitor?
Thanks for all your help

[Armadillo]

Highly likely it is a resistor and 6M ohm means it's open circuited.
Just measure the good one, duplicate the value of the resistor from the good port on the right and replace this component on the bad port. I suppose anywhere less than 10Kohm.

But you will need to know SMD rework. Stuck in between the chock and the electrolytic cap is a tight position.
Man!, hot tweezer can't do it, only hot air or use 2 soldering pencil might do it.
Careful not to melt vicinity plastic.

Edit: If you have never done smd rework, just pay someone to do it, cause it will not be that easy to reach.

[TheQuentincc]

Thanks for your reply, but for the soldering I planed to remove the chock and the cap to have the space to work
What are the risk if it was a capacitor instead of a resistor?

Yeah I know about SMD rework with my soldering iron, all I tried fail
Thanks for the advice

[Armadillo]

MLCC caps are usually light brown in color.
2 pins Black looking are the resistors.

Edit: The plan to remove the choke and the electrolytic cap is a good idea. Share the experience once you have done it,  good or bad, we like to know, yeah!. Good Luck with the repair.
Step by Step photos would be a good contribution to the community. [including problems faced].

[TheQuentincc]

Yeah, I'll try to do it if it's me who do it

[wraper]

I don't think it could burn by itself. Something else should had caused this. If this resistor is connected directly to PCI-E slot, it could be caused by bad card or inserting it under voltage. Look for similarly placed resistor nearby the first PCI-E slot.

[TheQuentincc]

So, I tried the SMD one more time beforce start and it seems to be 4.6k ohm, that's strange, maybe the first time I didn't aim well the SMD, I also decided to test it with my diode tester and I can see 1V (maybe 0.9V I don't remember ) in the first way and 0.4V in the second way.
Now i'm very confuse :/

[Armadillo]

So, I tried the SMD one more time beforce start and it seems to be 4.6k ohm, that's strange, maybe the first time I didn't aim well the SMD, I also decided to test it with my diode tester and I can see 1V (maybe 0.9V I don't remember ) in the first way and 0.4V in the second way.
Now i'm very confuse :/

Don't use diode mode, cause you will be measuring other many semiconductor in parallels with the resistor.
Just use ohms and measure it. Anyway, at such low voltage and wattage, manufacturer only uses very small range of resistors for such standard PCIe standard bus, no strange values, close enough for logic to works or enable lines to be pulled its OK.

It's my opinion and anyone here more qualified are welcome to correct me.

Are you saying that the resistor you measure 6M now measure 4.6K? Than its not burned.

[TheQuentincc]

Maybe I didn't aim well the first time I mesure it but now I have stable 4.6k ohm.
I think I will just melt a little bit the soldering point of the resistance

[EPTech]

Hi there,

If it should be 4k7 it cannot have fused with the voltages that are present on a MB. The burn marks you are seeing may be due to a badly done factory rework. Sure you can touch it up a little bit to be sure.
It may be for instance that the first time you measured on the pads and the second time you touched the surface of the resistor itself. In that case it could have been a bad soldering.

Happy reworking.

[Samogon]

Simple method to remove small smd parts like resistors ceramic caps, diodes, etc with just single soldering iron, shown by Louis Rossmann



Kudos to Louis, i personally used this technique with great success in tight places where even hot tweezers are fail to reach to the component.
And hot air tool will melt surrounding plastic.

[Armadillo]

Kudos to Louis, i personally used this technique with great success in tight places where even hot tweezers are fail to reach to the component.
And hot air tool will melt surrounding plastic.

Except in this case, there are 4 sky scrapers surrounding the 0603 component, and you can't even angled the soldering iron.
Imagine the soldering iron can only be tilted +/-10 degrees from the vertical.
The proposal to remove the choke and the electrolytic cap, will therefore render the case similar to the video to allow the soldering iron to tilt as the video.
Otherwise, I will like to see Louis do the 4 sky scrapers soldering stuff, won't you?

[Samogon]

Sure, removing through hole electrolytic cap and same through hole choke is a must process here. Then one will have enough workspace.