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Signs and Symptoms of an Underpowered PSU

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August 6, 2009 4:38:35 AM

What kinds of problems can having an underpowered PSU cause?

I recently built a system using a quad-core AMD Phenom II x4 940, 4GB 1066 RAM, an HIS Radeon HD 4850 1GB IceQ4, 1 DVD reading drive and one IDE 7200 RPM HDD.

I'm using a 380 Watt older Antec model (TruPower maybe?) with two +12V rails running at 16 and 18 amps. I haven't noticed a lack of performance in any of my games (Maxed out Fallout 3 (60FPS avg.), Oblivion (60FPS avg.), Crysis (25-35 FPS avg, at 1024x768) and my GPU and CPU temps always stay very low.

Recently though, when I first turn on my computer I will get a flash of display from my monitor, then the screen will turn black, although the monitor won't turn off or go into power saving mode and the computer will continue running. I will have to turn the monitor on and off several times (each time resulting in a flash of display followed by the black screen) until my display will finally stay, after which it works fine with no loss of display. Is this the result of an underpowered PSU? And can having an underpowered PSU cause damage to my system?

I figured this might be the case since my video card's recommended power supply is 450 Watts or greater (even though I know 12V amps are really more important in this case, my PSU'S 12V rails are weak too) and I heard having to weak of a power supply can cause instability.

August 6, 2009 4:46:31 AM

You have a problem with your monitor... Turning the monitor on and off does nothing to the video signal coming from your pc.

Could just not turn off the monitor when you turn off the pc.
a b ) Power supply
August 6, 2009 4:53:35 AM

Could be a problem with the monitor. Generally some of the signs of a straining PSU is fluctuating voltages. While it's best to see if it happens when your running something via a monitoring tool, it is sometimes evident on boot and you can see it in the PC health section of the BIOS. A cheap and strained PSU will fluctuate values like the 12v reading going from 11.1v to 12.9v pretty quickly. Of course the most tell tail sign is the high pitched whine that comes about when stressing the system, if you hear that turn it off ASAP lest ye end up with a toasty system :D .

Anyway I think it's your monitor that's flaking out.
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August 6, 2009 4:53:43 AM

Thanks, and good advice, I was kind of thinking it might be monitor oriented...do you think that power supply is too weak for that build though? And if it is could it cause damage to my components. Doesn't really make sense that it would to me, but I would just like to know for sure from someone with more experience than me.
a b ) Power supply
August 6, 2009 5:01:17 AM

Modern PSUs have nice things like overvolt protection and what not which basically makes the PSU shut down when it's strained too much rather than frying and causing a surge of power that would fry the rest of your components. Of course, in cheap and in older PSUs such protection can fail. I've fried a few boards my self with old PSUs, but it's always stuff I was gonna freecyle if I got it working so no big deal to me ^_^. Only time it really kinda inconvenience me was when I was working on my sisters computer and I had to RMA the board because the PSU took out the old Hard Drive and motherboard. The motherboard was the only in there that was new so I was pissed that I had to send it back, but luckily I got it replaced and passed it off as a faulty board :D .
a c 121 ) Power supply
August 6, 2009 4:50:48 PM

If it were a new Antec Earthwatts 380, I'd say it's enough, but if only because of its age, capacity may have diminished. You'd be doing no harm by replacing it, possibly with a little more powerful unit (e.g. Earthwatts 500W).
As the others have said though, the problem you're describing is most likely your monitor.
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