Need help with ID, Failing board.

[Rapideye]

Hello all,

I have this Asus Maximus III Formula that is randomly losing power.
The system appears to shut down, But the PSU is still powered up, The board appears to lose all power.
I have done all the usual troubleshooting and I have tested the PSU and all seems fine.
I suspect it could be a failing motherboard component.
I removed the board and had a good look around for any blown or suspicious looking components/caps.
All I could find on the rear of the board was some brittle brownish marks around the solder joints of 2 unidentified capacitors/chokes.
They appear to be fine topside of the board.

The brown square ones are the type I'm talking about, 1 is beside the 24pin and the other beside the 8pin 12v:





The markings are:

C.S
R20
09.23

Any idea what I am looking for as far as replacements go?

Cheers

[kc8adu]

Re: Need help with ID, Failing board.

likely just flux.

[y_not]

Re: Need help with ID, Failing board.

What's the psu?
Swap it with a known good one from a friend's system, IR another of your own.

Also, what you describe sounds like flux residue, but I see that you haven't posted a photo of thay part, did I miss something?
What are you pointing out in the photos you did post? They are quite blurry.

[PeteS in CA]

Re: Need help with ID, Failing board.

Concur re the brown stuff sounding like flux residue. Those brown components look like inductors, possibly/probably for noise suppression. It takes a fair amount of current to destroy an inductors, and unless the wire is really thin, it won't be invisible. Taking my guess a step further, I think the "R20" marking may mean 200nH (i.e. .2 uH), and the "1R0" marking on those dark grey boxes may mean 1.0uH (nH = nano-Henries; uH = micro-Henries). I don't know where/how it started, but in value coding systems "R" is usually/universally used to designate a decimal point. The "09.23" may be the date code (23rd week of 2009), and "C.S" is probably the brand.

[PeteS in CA]

Re: Need help with ID, Failing board.

Also concur with y_n. Unless you see a cap on the motherboard that vented, the next "usual suspect" is the power supply. Some of the critical caps there can be seen without removing the top of the case, but not all. If you see a vented or obviously swollen cap through the air vents, you've found a problem that may be the problem. If you don't see anything through air vents, take off the top of the case. Look at the caps on the output side (near the big bundle of multicolored wires), the big cap(s) on the input side (rated for 200V or =/>400V) and the small electrolytic caps usually located between the two big heatsinks. I strongly suspect you'll see something bad in the power supply.