How To Repair Power Supplies

PSU Repair: A Case Written report

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Ability Supply Troubleshooting

Power Supply Troubleshooting

Foreword

I have never bothered going beyond re-capping output capacitors when repairing power supplies. Most of the time, I fix hardware because I hate throwing stuff away that should accept worked for much longer. Just now that I have an oscilloscope, I can poke effectually places I would not accept bothered with before. This repair is ane I had been meaning to take another stab at for nearly a yr. Why carp with a decade-sometime power supply? Considering I tin can! Should y'all use a decade-erstwhile power supply? Probably not.

Disclaimer

As usual when lilliputian inside line-powered equipment (and especially on the primary side), don't endeavor this yourself unless y'all're a trained professional. You presume all risks for any it is you make up one's mind to practice.

The Basics

Power supply failures can be a nightmare for a variety of reasons. Chances are that if yous used any estimator for more than a few years without swapping out its power supply for some reason along the manner, so y'all've experienced the joys of owning a senior or defective unit at least in one case.

The about common and well-known failure that gets heavily criticized in power supply reviews is depression-quality output filter capacitors. Many times, though, what this really points to is nether-rated capacitors. The aforementioned was true in my LCD repair tear-downward back in February. In near cases, the symptoms start with random shutdowns or restarts, random crashes, devices misbehaving, failure to plough on then on. But in some more extreme cases, they can lead to fume, burn and exploding components, hence our insistence on staying away from bottom-of-the-barrel power supplies if you lot want to reduce the gamble of blowing upwardly your PC or worse. If you have seen some of the tiered PSU lists out there, some of those tier-five units take a reputation for being outright unsafe.

When a ability supply failure is due to dying output caps, the cause is often obvious upon opening the unit of measurement: you volition encounter many capacitors with bulged tops, perhaps covered in dried electrolyte. These supplies can unremarkably exist brought dorsum to a perfectly usable state by re-capping them using appropriately-sized and -rated replacements. Other times, the problems run deeper than a basic cap makeover.

In whatsoever case, for well-nigh people, power supply troubleshooting often starts and ends with a paperclip test that tells them little beyond whether the supply might be completely dead, not responding to PS_ON# or at least sort-of working. A basic multimeter allows you lot to check what the 5VSB voltage actually is and what the other rail voltages are if the supply is able to plow on.

Sometimes, y'all also have catastrophic failures with the associated light show, sounds, smoke and smells. In those cases though, repairs do not make much sense, if they're even possible, due to all-encompassing harm to components and the circuit board itself.

Another limitation of the paperclip examination is that the power supply might not behave the same mode between in-system and stand-alone due to added board capacitance and load across the rails, so any measurements done in isolation may not be representative of what is causing system bug, farther complicating the troubleshooting procedure past introducing imitation positives and negatives.

When a paperclip and $eight multimeter are not enough to get to the bottom of the story, people normally call it quits and throw in a new power supply. Fortunately for me, this is merely 1 more than excuse to put my oscilloscope to piece of work, hopefully go a usable ability supply and write an entertaining story along the way.

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Daniel Sauvageau is a Contributing Author for Tom's Hardware Us. He'southward known for his characteristic tear-downs of components and peripherals.