Helping people with computers... one answer at a time.
Computer power supplies can fail, and not always in sudden and obvious ways. Failures can be gradual, and can manifest in many different ways.
My machine locked up sometime overnight, and when I rebooted the memory test took forever. I thought it had frozen at that point, since it wouldn't even let me into the BIOS, but eventually did boot into Windows. Prior to this I had run a memory test program, and it had, in fact, shown errors, but those went away after I re-seated the memory cards on my motherboard. Someone mentioned that the power supply might be the cause, is that possible?
Most folks think a power supply failure will be catastrophic ... bright lights, flashes and smoke followed by no power; or just the sudden "no power" part without all the excitement.
The reality is often more mundane, and, for lack of a better word, at times even sneaky.
Power supplies can fail in a number of ways, and the catastrophic failures I mention are certainly possible.
What happens more frequently, though, is that the power supply slowly begins to not be able to provide enough power to run the machine. That can happen for a number of reasons, the most common being adding more hardware to the machine that causes the entire machine to require more power than the supply can provide.
Power supplies can also fail gradually over time. Perhaps it'll slowly drop the voltage it's supplying; the expected 12 volt output will start dropping to something less than that. How much less gets worse and worse over time until something finally gives.
What might fail actually depends on the tolerance of the various components in your computer. Many are quite tolerant and will run with an amazingly off-spec voltage, and others not so much. Sooner or later the component with the least tolerance may start to show errors, which themselves could be anything from incremental hiccups and crashes to a sudden catastrophic failure.
It appears that it's often the memory that shows the symptoms first (though not always). Reseating the memory could have temporarily improved the connection allowing the memory to get just enough more to be ok for a while, but if the power supply continues to get worse, that's not a permanent fix.
So if it could be the power supply, but it could be the memory, or it could be something else, how's a person to know what to do?
When it happened to me some time ago, I guessed. I replaced the power supply in a machine that started misbehaving, and sure enough it began to work reliably again. My guess was an educated one, though, as I had added hardware to the machine, increasing its power requirements, so when I replaced the power supply I made sure to replace it with one with a higher wattage rating.
If you're not comfortable guessing, it might be time to call in a technician who can actually diagnose where the problem really is. Determining with any certainly exactly what's contributing to broken behavior is not easy. In fact, many times even the technicians will simply swap parts until things start working. In effect they, too, are guessing.
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