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Power supply issues

pro2A

Hell, It's about time!
I recently bought a new HP Pavilion in a box at staples to replace my other aging computer. I wanted to upgrade the factory video card...

So I opened it up and looked at what slots it had, and I noticed a two PCI-E x1 and one PCI-E x16. So I went back up to Staples and looked at video cards for the PCI-E x16 slot, and ended up picking up a PNY GeForce 9400 GT 1024MB card. I came home, plugged it in and it didn't work... I did a little troubleshooting and determined my power supply wasn't adequate (I had a 250Watt). No problem, I figured I just needed to upgrade the power supply and I would be good to go. The VC required a minimum 300 watt supply.

I ordered a new supply online and I got it today (400 Watt). I carefully matched the new wires with the old wires to make sure everything matched. I even made sure it turned on before I screwed the PSU into the case. It worked perfectly.

I powered it down happy that it worked, took the old supply out and put the new one in. I powered it up again... it was fine. Then I powered down and unplugged everything to put my video card in. After making sure everything was plugged in nice and tight, I powered it back up with the new video card. It started up but no signal... I realized I forgot to plug the power cord from the VC to the mobo. I plugged it in and the restarted.

I got nothing. The computer turned on, then turned off and kept repeating this until I unplugged it.

So I removed the video card and tried powering up again. Nothing. All it did was start up for a second then switch off... it kept doing this until I unplugged it again.

So then I plugged in my old power supply, and it doesn't work either... it does the same thing.

I know my way around my computer pretty good, but I'm by no means an expert. Does anyone know what the problem may be here?
 

Arcadoc

Registered Member
It sounds like the CPU isn't letting the power supply run. So let's test the power supply. The CPU sends a "start" signal to the power supply to run, so we want to make sure of what's happening.
Unplug the power supply from EVERYTHING. Look on the 20 pin plug, count over to the 4th pin from the left. It should have a green wire attached to it. That's the START signal wire. Now you'll need to take a short piece of bare wire, or even a paper clip, and short that green wire to either of the black wires next to it. With that done, and NONE of the power supply plugs plugged into anything, plug the AC cord into the power supply and switch it on. The power supply should now start up and run.
If the power supply comes on and runs, the CPU is bad.
 

pro2A

Hell, It's about time!
It sounds like the CPU isn't letting the power supply run. So let's test the power supply. The CPU sends a "start" signal to the power supply to run, so we want to make sure of what's happening.
Unplug the power supply from EVERYTHING. Look on the 20 pin plug, count over to the 4th pin from the left. It should have a green wire attached to it. That's the START signal wire. Now you'll need to take a short piece of bare wire, or even a paper clip, and short that green wire to either of the black wires next to it. With that done, and NONE of the power supply plugs plugged into anything, plug the AC cord into the power supply and switch it on. The power supply should now start up and run.
If the power supply comes on and runs, the CPU is bad.
I don't think the power supply is the problem. 1. it's brand new and 2. The light on the back stays on during all of this.

I'm at a loss here.
 

pro2A

Hell, It's about time!
I don't think so either, but I'd rather know for sure than just being "at a loss".
Well I did the paper clip thing, and it didn't even turn on. I plugged it all back in, took out everything except the CPU, fan, motherboard and power supply. Still started, then reset...

I've tried everything I can think of. The short started after I put the new video card in. (I've since taken it out)
------
My initial fear is I shorted the mother board..... argh... even after all the checking before I got my new power supply.
 
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Arcadoc

Registered Member
Even if the motherboard got shorted, the power supply should still start up. I think something else is going on. Could you have popped a circuit breaker for the AC outlet?
 

Mirage

Secret Agent
Staff member
V.I.P.
This is weird. Try putting the old power supply back in and seeing if that works properly like it did before.

I've never heard of a power supply causing problems like this. It seems like the problems started when you put the new video card in. Did you make sure it was securely in before you turned the computer back on?

The only changes were a new power supply and a new video card, right? It worked before but not after these two new things were added?
 

dDave

Well-Known Member
V.I.P.
I realized I forgot to plug the power cord from the VC to the mobo. I plugged it in and the restarted.
Wait, did you do this while the computer was on? You're definitely not supposed to connect or disconnect anything inside the case when the computer is on.

This may sound a bit odd but make sure that all of your RAM is seated correctly, I accidentally bumped the ram a little bit when I changed out my video card when my old one died and initially I thought that the computer simply wasn't working.

If I were you I would start with the RAM and make sure that's correctly placed and is all the way into the DIMMs then if that doesn't fix it then I would recommend taking out all of your cards, PCI cards, video card, and disconnecting all of your hard drives and reconnecting them, that's worked for me in the past.
 

pro2A

Hell, It's about time!
Wait, did you do this while the computer was on? You're definitely not supposed to connect or disconnect anything inside the case when the computer is on.
I never do this :lol: Come on now :shake:

If I were you I would start with the RAM and make sure that's correctly placed and is all the way into the DIMMs then if that doesn't fix it then I would recommend taking out all of your cards, PCI cards, video card, and disconnecting all of your hard drives and reconnecting them, that's worked for me in the past.

This may sound a bit odd but make sure that all of your RAM is seated correctly, I accidentally bumped the ram a little bit when I changed out my video card when my old one died and initially I thought that the computer simply wasn't working.
I've actually taken everything out over and over again and reinserted everything 3 times at least. Nothing. Right now I have the motherboard on my wood desk checking all the connections bit by bit...
 

Arcadoc

Registered Member
You might want to get away from it tonight and then look at it again tomorrow. You'll have a fresh outlook on it and chances are you'll find that the problem is something simple that you're overlooking tonight.
 
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