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Serviceman's Log

Nothing comes even close to computers when ranking gear that's stuffed by consumers. As a result, I usually try to avoid fixing them but niece Duck's computer was different.

I have a niece who, at the tender age of three, was nicknamed "Duck". Well, Duck stuck and now at the even more tender age of 16, she’s still lumbered with that stupid name.

Recently, Duck’s computer failed and who better to fix it than this little black duck? The complaint was that the computer was dead. Not even the power supply was starting up.

Click for larger image

When the box arrived, I hooked it up and pressed the power switch. Nothing happened – it was as dead as a dodo.

This was going to be easy. After all, as everyone knows, if you press the power switch and nothing happens, it’s just got to be the power supply. Yeah, right!

When I removed the side panel, I immediately spotted two obviously faulty electrolytic capacitors between the processor and the memory sockets. Both had bulging tops which were covered in a brown crust due to leaking electrolyte. Then I spotted two more identical capacitors with bulging tops and leaking electrolyte in another section of the motherboard.

So it was beginning to appear that it was a motherboard fault that was preventing the power supply from starting up. That’s because, on an ATX machine, the power switch is connected to two pins on the motherboard and it’s the motherboard that then starts the power supply (via the main connector) when the power switch is pressed.

The question was, was it just the capacitors that were faulty or had something else on the motherboard failed as well? There was only one way to find out and that was to replace them. If it worked, it worked. If it didn’t, then the motherboard would be a "bin job".

I removed the motherboard and took a closer look at the leaking capacitors. They were all 3300mF 6.3V types branded "GSC". A quick Google of "GSC 3300mF" showed that these blighters have caused problems on lots of other motherboards over the years, not just on this 6-year-old Gigabyte GA-7VKML.

Before replacing the motherboard capacitors, I decided to test the power supply. When not hooked up to a motherboard, most ATX supplies can be started simply by applying power and shorting the green wire on the main connector plug (ie, the one that plugs into the motherboard) to an adjacent black wire (ground).

It’s also a good idea to connect a load, as some supplies won’t start without one. In this case, I connected an old floppy drive to the supply and used a paper clip to short the green and black wires on the plug. The power supply fan immediately burst into life and I was able to confirm that the +5V and +12V rails were present on the disk drive connectors.

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