PTGD1-LA 1 cap in backwards ???

[chevelle_nut]

First off a confession, and a self nomination for bonehead of the week. I took in an HP media center pc with an ASUS PTGD1-LA motherboard. No power up was the issue. So I look inside and see the VRM section has all 4 caps bulged, 2 others 820uf @ 6.3v bulged as well. A quick peek inside the 300w P.S. reveals 3 more 2 (2200uf @ 16v) and 1 (1000uf @ 10v). So I replace them all, test P.S. <checks good> and power up motherboard. It spins fans for 1~2 seconds and shuts down. Seems like P.S. is crow barring so maybe it is not fixed after all. (note: customer has added additional drive and high-end video card) I was thinking maybe it just did not have enough oooomph, so I put in a bench 750W. Powered up again everthing spins then about 3 seconds later POOF, POOF, POOF, POOF all the new VRM caps let loose the magic smoke. So I go to bed.

Today I take it apart again to do the autopsy. Apparently those little stripes on the side of the caps means something <doh>. I put them in backwards. < double doh, hence my nomination > I replace the 4 grenades in the VRM and reverse the 2 820's, and a quick power up with the original 300w PS. It spins up, stays running. I want to reconnect drives and video card but as I begin double checking everything ALL the other 'lytics on the board - except 1 are in the correct orientation. By the SATA connectors is c285 a 1000uf @ 10 that is lined up opposite all the others. Has anyone else seen this ? Is it o.k. to leave it as is, or should I pursue this. My brain hurts.

[mockingbird]

Re: PTGD1-LA 1 cap in backwards ???

Asus motherboards -

The stripe on the capacitor should face the OPPOSITE direction of the white half of the circle.

[shovenose]

Re: PTGD1-LA 1 cap in backwards ???

Not on all asus mobos.

[shovenose]

Re: PTGD1-LA 1 cap in backwards ???

You also must replace the bad caps in the power supply. Or else the new mobo caps will die sgsin soon and the system wont work in the first place!

[chevelle_nut]

Re: PTGD1-LA 1 cap in backwards ???

Asus motherboards -

The stripe on the capacitor should face the OPPOSITE direction of the white half of the circle.

That is how I put them in -the second time... Yes, I replaced the PS caps as well. The one cap in question is actually installed stripe on the white half. The machine is up and running like that. It is on the other bench running updates.

[momaka]

Re: PTGD1-LA 1 cap in backwards ???

The best strategy is to take note of the orientation of the original caps before recapping the motherboard. Unfortunately, that seems too late to do in your case.

So, one way to check if the orientation of a cap is correct is to use your multimeter. Just put it on resistance (preferably lowest setting), and see if the negative (striped) side of the cap is connected to ground (if it is, you'll see zero resistance). This is how *most* caps should be connected. The only exception is caps on the -5v and -12v rails and perhaps some of the small caps.

[chevelle_nut]

Re: PTGD1-LA 1 cap in backwards ???

An FYI here:

Turns out that one (inserted wrong at factory) bulged while it was on the bench. I guess fixing all the other problems finally made it let go. It still runs fine with no outward symptoms, I was just giving it the one final visual for dust bunnies before I closed it up and shipped it. When I replace it I will check voltage before I insert new cap, just to be safe.