ATX Supply

supplyFrontRemember that ATX power supply that I fried last year? I replaced it with another mail-ordered supply and then it sat on the shelf long enough for me to get around to fixing it: a new regulator, some MOVs, a cap and the fuse, and it was ready for action — except I had no computer to install it in. I kind of doubt that I’ll build another tower form-factor computer, so I turned it into a high current bench power supply.

It has to be more than ten years since I’ve done this, and I believe the last time I didn’t even have an ATX supply. At that time, supplies needed a hefty load to get going and remain stable. I recall using a car headlight. Literally: an old-style (maybe halogen?) automotive headlight. I reviewed a couple videos on the subject to see what people were doing with more recent supplies and found one that I liked and more or less followed.

I found that I got pretty good stability and regulation using a 15 ohm resistor on the 5V line, a 1/3 amp load. I had a chunky sandbar resistor in the junque box rated for 5W, so no problem to dissipate this 1.65W. I heat-shrunk the resistor and checked that the temperature of the resistor in operation was reasonable.

With that relatively minimal load, the power supply turns on, and all voltages are close to nominal. Maybe they would be more spot on with more loading, but it’s good enough for my purposes. Since this is a non-current limited supply, I only foresee using it when I need a lot of current or upstream of something more regulated.

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