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How bad is this voltage reading?

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Ken B.

Feb 22, 2006
I am building a junky old school PC for video surveillance. Just one or two USB cameras, that is all the PC will have attached to it besides the mainboard/CPU (1.8Ghz single core Turion)/RAM and a video card. I will be using Linux Mint as OS.

Checking out the power supply, it is a "Skyhawk" brand, about 200 watts or so. It looks OK, although it is a bit lightweight. I did the paper clip thing to allow the PSU to power on without being hooked up to the PC. I then tested with my Digital multimeter both 4pin molex peripheral connectors and the main 20pin ATX connector, they all read about 10.75-10.80V on the 12V line. The 5V line is more in spec, at 5.05V, so I'm not concerned about that one.

Is that 12V line reading really bad (too low)? Or is it reading that low because I did the paper clip thingy instead of hooking the PSU up to the PC?
So this reading isn't just because the PSU isn't hooked up (no load) to anything, right? Even if it were, it would probably still read the same?
So this reading isn't just because the PSU isn't hooked up (no load) to anything, right? Even if it were, it would probably still read the same?


Power supply is a boat anchor now. Imagine what you might find with a load put on it!
trash the power supply and get yourself a 300 watt SPI power supply.

does anyone think im wrong for suggesting him this supply? becuase i have had two that have been working great for years already.
Many older design PSUs won't put out the right voltages without loads of well over 1 amp per rail, and I have a vintage 1999 Delta that needs at least 2-3 amps on its +5V rail or else the +12V rail would be too low, like +10.62V, to let a hard disk spin. So test with a realistic load, like a motherboard.
It's definitely worth plugging a bunch of old HDDs or something into it to get a load, if it's old and group regulated it may, as LMC said, cope poorly with no load.

Many more modern designs still don't appreciate it (DC-DC bits are fine, others less so), but they usually have voltages that are close but bad ripple.

The above said, if it's looking for a solid 5V load (with that old of a PSU, you almost certainly are) you're pretty much stuck with a motherboard if you don't feel like soldering. There aren't many things other than an old motherboard that load 5V heavily.

I'd peer through the fan grill with a flashlight and check the caps if you can, or pop the top off (do not touch anything shiny inside. Ideally don't touch anything inside. Touching the wrong thing can kill you rather abruptly) and look at the tops of the caps. If they're flat, put the lid back on and hook it up to the motherboard and see what happens.
If they're bulging/leaking/dead, find another one.
That voltage is way too low. Junk that thing and get yourself a good unit.

ATX specification for 12 Volt rail is 11.4-12.6V. Most good power supplies are somewhere around 11.8-12.2V.

I had one that only put out 11.45V. It would run a system like that, but I didn't feel good about using it after I found out the voltage output was so low. I stopped using it and bought myself a good power supply (Corsair HX620 is the good one I bought, which was decent at the time).