Asus A7n266 - interesting problem

[Pud]

Hi all,

Have just recently recapped a blown Asus A7n266-VM motherboard.
Everything booted fine - with no problems and the PSU checked out ok.
Had the system running for about 15 minutes until i realised that three of the eight caps i had changed had started to bulge.
Thought it was a bit odd as i have never had this problem (the Samxon caps i use are pretty damn good) and thought it must have been my soldering work perhaps they weren't positioned very well.
Looked on the board and noticed i forgot to install two caps above them (!). so i installed the two caps i had overlooked and replaced the three that popped before with some new Rubycons. thought everything would be sweet now and fired it up until about 5 minutes later this time the three caps exploded and spat all over my face!

The three in question are all situated next to each other in a horizontal row just to the right of the audio/game port connectors and to the left of the AGP slot. They were rated at 3300uf 6.3v as were the two i missed (which are located just underneath the cpu.

All of the other caps i have changed are fine it's just those three.

i wanted to replace them again and install a different power supply but i have just run out of caps so i must order again before i can try anything.

Any suggestions? higher voltage rated caps? maybe even higher caps and a new psu?

I appreciate any assistance as the law firm that it came from are getting edgy and want their system back!!

Thanks heaps.

Anthony

[arneson]

Re: Asus A7n266 - interesting problem

It's difficult to answer someone called Pud.

Someone else may give you other possiblities but from your description, 15 minutes to bulge, then 5 minutes to explode, says caps in backwards to me.

[linuxguru]

Re: Asus A7n266 - interesting problem

1) You inserted the caps with reverse polarity; and/or
2) The silkscreen at those locations is in error, and shows reversed polarity; and/or
3) Your PSU is utterly screwed and is seriously overvolting some rails; and/or
4) Your VRM FETs are shorted and passing the input voltage (+12v) to the output side (Vcore or +3.3v).

By now, you probably have a serious amount of stuff to debug - a new mobo is the better solution. If they're a law firm, billing them $100 for a new mobo is no big deal.

[Rainbow]

Re: Asus A7n266 - interesting problem

Asus (and ASRock) boards use reversed marking! The white half of the circle means positive (see other caps on the board).

[Topcat]

Re: Asus A7n266 - interesting problem

Asus (and ASRock) boards use reversed marking! The white half of the circle means positive (see other caps on the board).

^
That's what happened. ALWAYS look at how the old caps are positioned first. Some IBM and Dell boards are the same way.

[willawake]

Re: Asus A7n266 - interesting problem

Asus (and ASRock) boards use reversed marking!

that is correct. you may be lucky
although the second boot was not recommended

If they're a law firm, billing them $100 for a new mobo is no big deal.

i agree. they probably have no idea what they cost anyway. they just want it working immediately

[Pud]

Re: Asus A7n266 - interesting problem

Asus (and ASRock) boards use reversed marking! The white half of the circle means positive (see other caps on the board).

Holy moses. You guys are all right - i didn't even realise when i pulled them off i just assumed they were like every other board.

This asus board does use a reverse polarity the white marking is in fact positive NOT negative... i just took it for granted that that's how it is without even checking (as i normally do).

some new caps and in the right way and i should be right as rain.

i was told by a number of different sources that the mosfets just above them are probably putting out 12v instead of 6.3v on the rail so was about to toss the board out until i read everyone's replies.

a new board wouldn't normally be a problem but being a socket A board they'd be up for new ram, new board, and a new processor as well as a reinstall of windows and an onsite service charge for me to set it up again on their network. that's when they might have a problem with a new board!

thanks for your help i really appreciate it!!

Pud..

and btw Pud isn't a rude word in australia although i hear it is in the us/canada??

[starfury1]

Re: Asus A7n266 - interesting problem

Pud
Pudding like Christmas pudding....
my brothers nic is pud and his in the states
LOL

I am from OZ too

I now take a digital photo or 3 of anything I work on so I got some ref photos
so I can be sure of how it was when my short term memory fails

Hope it work out alright for you