Power only flashes on for split second

[gregs7726]

Hello,

I dont know if I have a second dead PSU or I dont know...

I am putting together a new PC and I purchased all new parts, except for my graphics card.
The new PC is:
- DFI Lanparty 875P motherboard.
- Pentium 4 3.4GHz CPU(LGA775)
- Two 1 GIG OCZ 3200 400DDR Ram sinks
- ATI 9800AIW Pro 128
- Two Western Digital Raptor 74GB SATA hard drives
- NEC Dual Layer DVD write drive
- Generic 16x DVD drive
- Thermaltake Tsunami case that comes with 400 Watt power supply(model XP480).
(I know I spent way too much, but hey HL2 just came out :P)

When I plug everything in and attempt to power up the system, the power just flashes on for a split second, and thats it. If I continue to hold down the power on button(there is one conviently on the motherboard), it just continues to flash on and off rapidly, never fully turning on.(About once per second)

I instantly thought there must be something bad about the power supply.

I have a power supply around the house that I bought a while ago but never used. It is a CoolMax ATX 350 Watt Fanless Switching Power Supply. When I plug everything into this power supply, it did the power flashing for about 2 or 3 cycles but then it booted up fine! The system starts to run and I had things working and was setting the clock in CMOS settup. Everything seems to be fine with that power supply except for that initial flashes.

I took everything apart and took the case back to the store. I told them the power supply must be bad. They gave me a new case. When I took this home and plugged everything in I had the same issue.

Both times I tried unplugging anything that was not necesarry to get the system to boot up with just the bare components, but it still does not work with the Thermaltake XP480 power supply.

I read through all the power supply issue posts I could find on this site. I took the 400Watt power supply out of the case and tried that thinking it could be a ground problem(the 350Watt power supply worked and it was out of the case), but that did not change things.

It says in the manual that my DFI board that it is STRONGLY recomended that the power supply should be 400 Watt's or more.

I have a couple of questions:

What could cause the 400Watt power supply to only stay in this weird flashing on and off mode?

It is STRONGLY recomended by the DFI Motherboard manual that I use a 400 Watt power supply or higher. If I use a 350 Watt power supply what sort of
issue's would I run into?

Hopefully someone can help me.
Thanks! Greg

I dont know if this helps, but here is some of the info on the stickers on the power supply's(I hope this will align properly on the post):

XP480
AC Input: 115/230V 8/6A
Frequency: 50 - 60 Hz
Peak Load: 500W
DC output
+5V +3.3V +12V -5V -12V +5VSB
28A 20A 17A 0.5A 0.8A 2.0A

Coolmax Model: FL-350ATX(CF-350)
AC Input: 115V~ 230V~
Current: 8A 4A
Frequency: 50 - 60 Hz

DC Ouput |+3.3V | +5V | +12V | -5V |-12V |+5Vse |PS-ON |POK |COM |
_________|_28A_|_35A _|_15A _| 0.5A| 0.8A | 2.5A |remote|P.G. |Return|
MAX______|____ 200W __| 180W|_____|_____|_____|_________________|
_________|_______325.4W_____|_2.5W|9.6W|12.5W|____ ______________|

[risk_reversal]

When you say that you tried a barebones set up, presumably you had cpu, vga & 1 stick of ram (no need for hdd even). Is that correct?

Possible areas that would be high on my list to solve your problem.

1. You have fairly large ram sticks 1gb each. Some boards have problems with this type of set up. Try to borrow a smaller stick of ram to see whether this resolves issue.

2. PSU. You listed the specs to each of the psus and my opinion is that they are both of insufficient strength to power your rig. I use an AMD cpu and it consumes about 70-75w. I believe that P4's consume even more. In addition, ram consumes about 10w (from the 5v rails) for each 128Mb. I am not sure if you can borrow a better psu from a friend to try out.

Hope this helps

[Sylvander]

I wonder if this might apply? :confused:
http://www.pcguide.com/ref/power/sup/funcPowerGood-c.html