Saturday, December 8, 2012

ATX PSU Repair

As noted in the HTPC build I used a repaired Ultra D0408 ATX PSU. I was using it in the P4 and it would work fine for a long time, then just start randomly rebooting, then it would be fine again. At first I thought it was the motherboard or ram, but then discovered if i bumped the desk or case it would almost always start acting up. Of course that screams "Something's Loose!".

So I had the opportunity to remove it and inspect it as I did my upgrade. Here's what I found:

Caps all look ok, no bulges, etc.
Cover Off
Be very careful when taking these apart, Voltages may remain for a very long time. I held it by the wires to remove the board, flipped it over and checked those 2 big caps (upper left). They had less than 2VDC in them, but depending on the failure it could be over 300VDC.

Bottom of board
Now we can see something, I don't know if you can see it in the above picture but in the lower right corner there is a capacitor that has come loose from the solder. It is on the 12V rail. The heatsink on the left of the unit also has a bad solder joint, but it appears to be isolated.
Bad solder joint (about in center)
So I soldered it up and will try it out. These units are cheap, so it doesn't pay to spend much time fixing them, but sometimes it's something simple like this. It's also practice for things like the Parrallax. Time will tell if that was the problem or if it's something more serious.

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