Faulty Motherboard Capacitor

[IdlePhaedrus]

Hi All,

I am pretty certain I have a faulty capacitor on my motherboard. It is an old machine, and it needs to be replaced, but if I keep it going for another year or two that would be great too.

So, old machine, does not start after soft shut-down from windows (intermittent), unless all power is removed for some time, usually about 10-15 minutes.

Is there anyone in Cape Town who can test the capacitors on the motherboard and replace them if necessary at a reasonable fee?

The capacitor is probably between the power supply and the main board, and there probably aren't too many of them.

Thoughts?

Phaedrus

 

[Defiler]

I once replaced a capacitor on my old nforce1 motherboard without any problems, one way to check if a capacitor is on its way out is to look very carefully for any oil/goo leaking out. I was lucky and had a capacitor with the same value as the one I that was needing replacement as I used to build a lot of electronic kits and things when I was younger...

 

[Franna]

Have a look at http://www.badcaps.net/ to see sample pictures.

 

[The_Unbeliever]

Be careful - as that electrolyte/oil/goo is highly toxic...

 

[Ry4n]

I know a guy in Southern Suburbs - Cape Town that can do it for a reasonable fee he usally charges me R100-200. PM me for mobile number.

 

[sn3rd]

An electrolytic capacitor can be bad even if it isn't leaking/bulging/swelling.

The ACTUAL only way to test for certain is to measure the transient response of the capacitor, but this will require some equipment that I'm fairly sure you don't have.

What exactly is connected between your power supply and mainboard, aside from the cable?

While it should be fine to replace just the affected caps (if you can narrow it down to that), it's a good idea to replace them all with good caps. Otherwise you'll spend money having it done now, and then in a short while, some other caps will start to go too.

 

[gregmcc]

What motherboard is it. I've replaced a few on some IBM boards - they all seem to have a common problem after a few years.

 

[IdlePhaedrus]

Thanks everyone for your responses. I think I will take Ry4n up on his offer.

To answer your questions, it is an old small form factor Aopen XC Cube. The affected capacitor only affects startup, once the machine is running, it does not freeze or BSOD. To start it all power has to be removed (unplugged) for a few minutes, presumably so the capacitor discharges or something.

When the power is re-applied, and the start button quickly pressed, then the machine starts. Otherwise, the fans will attempt to swing, then stop, the blue light around the on button will briefly glow, and then nothing happens, no post etc.

 

[Barge]

Interesting post and links. All 5 of the 3300uF 6.3v caps were leaking on my GA-7zxe, socket-A motherboard. I've heard that batches of similar caps can be sub-standard. I just bought some new caps from Communica in Woodstock/Salt River. I did not feel like waiting for the 105C rated ones (R2.90 each) and just got some 85C ones (R2.10 each). I don't reckon the system temp should get so high. It's usually around 36C.

I already had a 25w Weller soldering iron and some silver solder. I bought a solder suction pump to clean out the holes on one website's advice. The replacements Caps were only available in 3300uF 10v or more rating. The higher the voltage, the fatter the cap, so these did not fit perfectly flush on the motherboard in 2 cases. I do not have an anti-static wrist strap, but worked touching my earthed PC chassis to avoid ESD frying anything.

The desoldering pump seemed pretty ineffective but it was only about R16 so not much loss.[EDIT: I used it on another job and it worked fine. Using it for the 1st time I guess I was a bad workman blaming his tools]. I then took the advice of another website and instead of cleaning out the holes, pushed the stalks through a little too far, put extra solder on, and pull them back into the hole so that the hole is filled with solder. I understand that this is to be sure the caps make contact with all layers of the multi-layer MB.

I already had some heatsink compound, which I used when re-seating the heatsink on the CPU.

It seems to have worked.

Since re-assembly, I've had an issue with some corrupt files on my one harddrive. I'm not sure how this might relate to the repair. Maybe related to how I handled the drive when I had it out of the PC?? Chkdsk didn't pick up anything and I replaced the corrupt files. Everything else seems great. Perhaps I've given a little more life to my old system? Certainly hope so.