Computer runs fine, reboots fine, but won't turn on again after shut down

[kellehair]

So like the topic says I can use my comp with no probs, I can reboot with no probs, but after I shut down I can't turn it back on again. If I open the case and unplug the HDD it will power up and then I can power down, reconnect the HDD and boot up normally. And once it's up, it runs perfectly, not the slightest hint of a problem.

Funny thing is, this is an old build, all I did was move it into a new case with a new PSU. I was using a 550W Antec NeoHE. Now I'm using a 450W Antec WhateverCameWithTheCase. This New PSU probably isn't the best and my proc and RAM are OC'ed so that night be a problem. Vid card isn't though and I'm not gaming on this box. Plus all these settings worked in my previous box.

Opty 165
DFI LanParty UT NF4 SLI-DR
2x1 GB OCZ Platinum
7900GT
WD SATA II 250GB
XP Pro

 

[gtechie]

I'd probably switch out the PSU for a higher wattage. These days, a lot of things are power hogs. For new gaming PCs we build for customers, our minimum wattage we use is 500W and that only barely covers the low end builds. Also, since you are OC'ing, you will need a better PSU, or at least a higher wattage PSU.

Most case PSUs don't have good voltage rails so you may be pulling certain voltages too low from first power up but once it's up, it's fine for a bit. Also, when you power down real quick, connect the HDD, and it turns on just fine again, it's probably because there's still power in the caps so that your voltages don't drop too low again.

Here's how the power work. When you first turn on your computer, not only does the PSU power up your components, it also has to charge up all the caps in the PSU, the board, your vid card, and so forth. Once all the caps are charged up, then your current drops down to normal operating values. In the beginning, your current spikes up to charge everything but if your PSU can't handle the current spike needed in the beginning, the voltage will drop considerably.

Basically, most case PSUs aren't that great with voltage and current ratings. I would get a bigger one and then you should be fine.

 

[robisbell]

you're under powering it and it's struggling to boot with less power.

 

[kellehair]

I appreciate the help. I have an incredibly hard time believing 450W isn't enough for the few paltry components in this case. But I don't have any better ideas. Tonight I'll try lowering the OC or maybe unplugging the optical drive just to see if that makes a difference.

So what's a 450W PSU good for these days, powering the case fans?

 

[robisbell]

you mean 500 or 550 watts.

I normally recommend PC Power and Cooling.

but Antec is a good backup.

http://www.newegg.com/Product/...x?Item=N82E16817371002

http://www.newegg.com/Product/...x?Item=N82E16817103941

 

[oynaz]

Originally posted by: robisbell
you're under powering it and it's struggling to boot with less power.

Not necessarily. That would probably result in an unstable system as well, and 450 watts should be enough for that system.

Why not try with the old PSU and see if the problem persists?

 

[robisbell]

well, he's having an issue running it with a 450, buthad no troubles with a 550 watt. the system needs more than what a 450 can offer at startup, and that also means the 450 can not support it if the system is put under a load.

 

[oynaz]

You are jumping to conclusions. While I agree that the PSU is a likely culprit, there are a host of other possibilities, for instance poor seating of RAM, a poorly seated graphics card, and a failing motherboard capacitor.

The OP is right, 450 watts should be plenty, though it is hard to get your hands on a quality PSU rated lower than 500 watts these days.

 

[robisbell]

I am not jumping to conclusions.

SATA 2 drive
7900 GT
DFI LanParty UT NF4 SLI-DR (firewire,gigabit,spdif,etc)
and the processor

at boot up, that puts a huge strain on a 450 watt psu, and don't forget he went from a 550watt that booted up the system without any issue, to a 450 watt. he cut out 100watts of power, that's a clue that only a blind man would ignore.

 

[kellehair]

OK, here's the conclusion of this story... I ordered up an 8400GS ($18 from buy.com, sweet deal). Popped that baby in and the problem disappeared. Despite the evidence I'm still somewhat unwilling to say that the PSU was underpowered. This new card doesn't use the PCIe power connector, which the previous card did, so that may have also been a cause. Either way I'd like to thank everyone for their help. BTW, my next PSU is gonna have one million watts, at least.

 

[seemingly random]

Originally posted by: kellehair
BTW, my next PSU is gonna have one million watts, at least.

And by the time you need another psu, these might exist - for the uninitiated suckers out there.

 

[robisbell]

well, it's still a psu issue, you've just avoided it for the moment. good luck.