What are "acceptable" power supply fluctuations??? - Techist - Tech Forum

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Old 03-03-2006, 07:47 AM   #1 (permalink)
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Default What are "acceptable" power supply fluctuations???

OK, I've been having a random reboot issue with my machine. I checked the power readings in the BIOS and was getting numbers that were off the marks of what they should be, but I'm not sure if they are acceptable or not. I have them written down at home, but what I can remember is that the +5V was giving me like 4.19 and the +12V was reading at 10.3 and jumping to either .2 above or .2 below that. Do I need a new power supply??

One more thing that might help solidify this as a PSU issue is that as soon as or 20 seconds after the Windows XP logo disappears and my desktop shows up, it reboots. Could this be because the system is starting to draw more power at this point and the PSU can't handle it, so it reboots?? And I hastily skipped some troubleshooting steps and replaced the motherboard already, so I'm pretty sure the readings are accurate. I'm kicking myself for doing that already

Thanks for the help!

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Old 03-03-2006, 07:50 AM   #2 (permalink)
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yeah, those readings are way too low.
either this means your motherboard isn't very accurate, or you need a new PSU.

I'd get a new PSU anyway

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Old 03-03-2006, 03:49 PM   #3 (permalink)
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Those are crazy low. Usually +/- 5% is what you're looking for.
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Old 03-04-2006, 10:56 AM   #4 (permalink)
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The 5V should read between 4.5V to 5.5V, 3.3V should read between 3.1V and 3.5V, and 12V should read between 10.8V and 13.2V.

The reading you get in BIOS are often inaccuarate.

You very likely need a new PSU
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