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Old 01-18-2010, 06:43 PM   #1
momaka
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Default Asus A7V8X-LA - bad caps?

I'm trying to fix my friend's computer - it's a HP Pavilion a620n with an Asus A7V8X-LA motherboard. The problem is that the computer doesn't want to post when turned on. No monitor activity, no beeps, just the fans turn on and the power and HD LEDs are lit. When the computer is powered, all of the keyboard lights flash quickly then turn off.

So far I've checked the PSU (a 250w HiPro) and there were no bad caps (all were Teapo). 5vsb is at 5.15v, so it should be good. All other rails are in spec, too. My friend said he also tried a different PSU and that didn't help.
I've also tried disconnecting everything and tested only the motherboard with the processor (an Athlon XP 3200+), both with and without RAM. Motherboard did not beep or give an error message when there was no RAM installed. Also tested with and without the AGP graphics card (motherboard has onboard video) - that didn't make a difference either.
Finally I tried resetting the CMOS via the motherboard jumpers as per the motherboard manual. With everything disconnected from the motherboard (except for the CPU, CPU fan, and SYS fan) and the CMOS reset, computer still wouldn't post or turn on the monitor.

Is it possible that the caps are bad, or is there something else wrong based on the above symptoms? I can power the computer on and off from the front switch just fine, which is telling me that the southbridge is working. So that leaves me with either a bad CPU (unlikely) or something else wrong with the motherboard.
As for the caps, none of them looked bulged. The motherboard has:
3x United Chemicon KZE 16v 1200uF 10mm dia. (VRM high)
8x Elite EB 6.3v 1500uF 8mm dia. (VRM low)
18x Ost RLS 6.3v 1000uF 8mm dia. (scattered throughout the board).

So, any ideas or thoughts?
Thanks.

Last edited by momaka; 01-18-2010 at 06:46 PM..
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Old 01-19-2010, 08:00 PM   #2
forrestm
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Default Re: Asus A7V8X-LA - bad caps?

I have an MSI K7N2 Delta (MS-6570) board with very similar symptoms - won't post or beep, but fans spin up OK, even when stripped to the bare minimum of components. PSU is an Enermax 300W.

The board has Panasonic caps around the CPU, which I'm assuming are OK, and also 16x 1000uF 6.3v OST caps scattered around the board, as well as 3 16v OST caps near the VRM area. All caps on the board look OK and show no signs of failing.

I was thinking of replacing all the OST caps, since they have a reputation for failing without showing any visible signs.

However I'm not sure if it would make any difference... Could it be an unrelated problem? Ideas anyone....? Is this a symptom of bad caps?????
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Old 01-20-2010, 03:15 PM   #3
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Default Re: Asus A7V8X-LA - bad caps?

Hmmm

I replaced all the 1000uF OST caps with Rubycon YXG's from another motherboard I had, but still no go. Perhaps the BGA solder joints on the southbridge have become stuffed and need a rework/reflow? The southbridge has no cooling
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Old 01-20-2010, 04:53 PM   #4
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Default Re: Asus A7V8X-LA - bad caps?

I installed the board with a different CPU, power supply and graphics card, and this morning the board works OK.

Still not sure what's wrong, it could be 1) power supply 2) faulty motherboard suspectible to temperature changes 3) something else..? Still need to do more testing.

I have tested all components in other PCs and they work fine (components from both previous and current configuration)

So to the OP I suggest you have a play around, try installing the board in a different system, etc. I would be keen to hear if you find a solution!!!
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Old 01-20-2010, 05:23 PM   #5
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Default Re: Asus A7V8X-LA - bad caps?

Trying the board again (same config) after an hour or so, and it doesn't work. Must be a problem with the mainboard.
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Old 01-20-2010, 05:24 PM   #6
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Default Re: Asus A7V8X-LA - bad caps?

Caps could be bad. It's common for them to fail without bloating. The KZE on the VRM in should be fine, but any of the others could be bad.
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Old 01-20-2010, 11:29 PM   #7
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Default Re: Asus A7V8X-LA - bad caps?

Quote:
Originally Posted by momaka
The problem is that the computer doesn't want to post when turned on. No monitor activity, no beeps, just the fans turn on and the power and HD LEDs are lit. When the computer is powered, all of the keyboard lights flash quickly then turn off.
@c_hegge: Is this a common symptom of bad capacitors?
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Old 01-21-2010, 12:32 AM   #8
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Default Re: Asus A7V8X-LA - bad caps?

Not posting may or may not be caused by bad caps. It depends which ones are bad and how bad they are. If the ESR goes to high on the VRM caps (or they fail open, letting no current at all pass through them) they may not let enough current to the CPU for it to post. I've re-capped boards before where they wouldn't post before the re-cap and worked fine after. Having said that, though, it can be caused by other things, such as a faulty northbridge.

In any case, though, there's no harm in trying. If re-capping doesn't get the board going, just pull the caps off and use them elsewhere, and all you've lost is a board that was dead anyway.
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Old 01-21-2010, 09:18 PM   #9
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Default Re: Asus A7V8X-LA - bad caps?

I agree that it's not always the caps that can cause a no-post problem, that's why I decided to ask here first. Since not too many people posted here, I guess there isn't a definite answer to that question. Perhaps I will try one more thing this weekend: heat up the caps with a hair drier. If that makes the computer work, then I'll know if it's the caps or not (or maybe a cold joint, but that's unlikely).
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Old 01-21-2010, 11:43 PM   #10
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Default Re: Asus A7V8X-LA - bad caps?

Warming them up may help, but it's still not a very definitive test. It can reduce the ESR, but it doesn't un-fail them
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Old 01-24-2010, 12:33 AM   #11
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Default Re: Asus A7V8X-LA - bad caps?

Sometimes that is enough of difference to make things work.
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Old 01-24-2010, 03:01 PM   #12
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Default Re: Asus A7V8X-LA - bad caps?

Quote:
Originally Posted by Pyr0Beast
Sometimes that is enough of difference to make things work.
I wasn't saying that it wouldn't work, I was just saying that, if it doesn't, it wouldn't entirely rule out the caps as being the problem
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Old 02-04-2010, 10:47 PM   #13
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Default Re: Asus A7V8X-LA - bad caps?

Well I tried heating up the caps with a drier last weekend. Got both the board and the caps pretty toasty. Computer still didn't post, though, so results are inconclusive. Also tried resetting CMOS by removing the battery. Battery has 3.06v so it should be good.
Unfortunately, I won't be replacing the capacitors. My friend said he's giving the computer to someone for the parts.
I did find one interesting thing, though - there's a SATA power cable that uses cheap connectors that splice through the wires. On the second (end) SATA connector, the wires are cut off after being spliced and there are some bare strands sticking out of each wire about 1mm. I wonder if this could have shorted something on the motherboard. That SATA power cable was unused and just dangling in the computer when I got it.
By the way, this power cable is an add-on and not from the HiPro PSU.
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Old 02-05-2010, 08:40 AM   #14
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Default Re: Asus A7V8X-LA - bad caps?

i cant believe that they spliced a wire in there and did not at lease put some electrical tape around it.. i think that one should go in the computer stupidity listing..
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Old 02-05-2010, 10:41 AM   #15
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Default Re: Asus A7V8X-LA - bad caps?

remove & refit the cpu.
i'v seen a p4 the other day that had a poor connection in the cpu socket.

never seen it before, but they are making stuff cheaper these days.
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Old 02-05-2010, 04:25 PM   #16
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Default Re: Asus A7V8X-LA - bad caps?

Quote:
Originally Posted by stj
remove & refit the cpu.
i'v seen a p4 the other day that had a poor connection in the cpu socket.

never seen it before, but they are making stuff cheaper these days.
I love it when you try to take off one of the newer processors and they stick to the heatsink. just rips right out of the socket, and there is nothing that you can do because the heatsink is so big that there is no way to release anything.. I always feel like I'm going to break one of the pins off the processor..
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Old 02-05-2010, 11:38 PM   #17
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Default Re: Asus A7V8X-LA - bad caps?

Quote:
Originally Posted by kaniki
I love it when you try to take off one of the newer processors and they stick to the heatsink. just rips right out of the socket, and there is nothing that you can do because the heatsink is so big that there is no way to release anything.. I always feel like I'm going to break one of the pins off the processor..
I've had that happen lots of times. Thankfully, I haven't had pins come off yet, although I probably will some time.
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Old 02-06-2010, 12:42 AM   #18
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Default Re: Asus A7V8X-LA - bad caps?

this only happens i think with dried silicone-grease.
i'v not had the chip rip out with arctic silver.
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Old 02-06-2010, 01:51 PM   #19
momaka
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Default Re: Asus A7V8X-LA - bad caps?

Quote:
Originally Posted by kaniki
i cant believe that they spliced a wire in there and did not at lease put some electrical tape around it..
Actually, that's how the cable was made from the factory. I guess I should have been more descriptive - the connectors use tap splices to connect to the wires. Still, you don't just cut wires and leave them like that.

Quote:
Originally Posted by stj
remove & refit the cpu.
Good idea. Seeing that we have a snow storm here, I don't think my friend will be comming anytime soon to pick up his computer so I might try it. However, I need to get some thermal compound first .
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Old 02-06-2010, 07:40 PM   #20
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Default Re: Asus A7V8X-LA - bad caps?

Quote:
Originally Posted by stj
this only happens i think with dried silicone-grease.
i'v not had the chip rip out with arctic silver.
actually, i had that happen to me quite a few times, and none of them were from dried out grease of any kind.. it was ore like the liquidy suction was greater then the small amount of force that keeps the 1 inch processor in place..
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