PC wont start

[aznn3rd]

I upgraded my HP PSU 250W to a NuPower 380W and while the system seems to be operating, the monitor doesn't detect a signal. It works when I replace the old PSU though. Any one know the cause of this issue?

 

[raybay]

One or more of your cables is incorrectly installed.

 

[aznn3rd]

So it would not be a compatibility issue? Because I double checked and made sure that all the wires were in the right places.

 

[mailpup]

Then perhaps it's defective.

 

[aznn3rd]

Well I have 2 HPs. One with a 380W and one with the original 250W. I was going to swap the two because the 380W HP was an older model whose PSU broke down, which I had replaced a few months ago. Now, I want to upgrade a Radeon 3850 to my newer HP and so I want to switch the PSUs. According to you guys, I should just reinspect the cables right (ie no proprietary or incompatibility issues)?

 

[Tedster]

did you hook up power to the graphics card?
Did you connect the video cables?

 

[aznn3rd]

I didn't install a graphics card yet, I'm still seeing if it works with the integrated graphics. As to video cables, my monitor is plugged into my mobo, if that's what you are talking about.

 

[mailpup]

If you've changed nothing else except the power supply and all the connections are correct and tight and you can't get get a signal to the monitor but you can with the old power supply, there must be something wrong with the PSU or one or more of its connectors. That's what it seems to me.

 

[aznn3rd]

I used the exact same connectors for both HPs and one works while the other has no video. I'm gonna try to hook up the 3850 to my monitor tomorrow and see if it works that way.

 

[aznn3rd]

so the main problem with my PSU is that for some reason the 20+4 pin doesn't provide enough power to send a signal to the monitor, even though the specs shows it being clearly superior to the PSU that came with my HP. This is really weird. Would a better PSU work?

 

[mailpup]

It's possible there is a problem with the 20+4 pin connection or if your motherboard uses the 2x2 P4 12V connector, that could be bad too. Possibly the PSU isn't putting out enough voltage on some of the wires. If your PSU turns out to be bad, a better PSU should work.

Have you tried the "bad" PSU in both of your HPs? Does it fail to work in both?

 

[aznn3rd]

it works on my old HP (a1123c)

 

[mailpup]

The Nupower 380W works in the old HP but not in the new HP?

 

[aznn3rd]

that is correct

 

[mailpup]

Possibly, despite the differences in wattage, the amps put out by the 380W are inadequate for the newer PC. The amps on the +12V rail or rails is usually the most important. Amps vary widely even on same wattage power supplies and often a higher wattage PSU will put out less amps than a lower wattage PSU. That's why you can't go by wattage alone. Better quality PSUs will tend to have better amperage ratings.

 

[aznn3rd]

the HP 12V: 13A
the NuPower 12V: 17A

Although as NuPower isn't exactly name brand, the 17A may not be a reliable number.

 

[mailpup]

The amp rating seem ok but I still think there is something wrong with the Nupower but I can't tell what it is.

 

[aznn3rd]

Hey guys, for those who care, I have found the cause of the problem. It seems that the HP a1123c had a proprietary PSU, which is why it wouldn't work on my newer computer. I found this out when borrowing my friend's PSU, which worked just fine.