PSU woes...

[Skillian]

OK, some background. For the last 6 months I have been running an Athlon64 3000+, 512MB 7900GT, 1GB RAM, 2 HDDs etc. from a crappy 350W PSU that came free with a £25 case 4 years ago.

No problems with stability, but recently the noise of my PC has been starting to bug me, so I bought a new PSU, heatsink/fan and case. The new power supply is a Seasonic S12-430.

I hooked everything up (built about 5 PCs now so getting quicker) and when I push the power button, the fans spin up for a second or two and that is it - nothing on the monitor.

After messing around pulling out components etc, I tried with my old PSU and instant success. This is a PSU with a 20-pin power cable and a 24-pin motherboard but still it works better than my new Seasonic.

I'm pretty pissed off right now so I'm going to bed, but I thought I'd post here and check any replies in the morning. Any ideas? Dead PSU?

Sorry for the long post.

[lynx]

What motherboard? I've seen exactly this problem myself with Biostar motherboards.

The problem may be that the motherboard requires -5V, but most of the latest PSU's (Seasonic included) don't supply it. Tagan PSUs are a good alternative, and they have the -5V supply.

[Skillian]

I believe the motherboard is a Foxconn NF4K8AC-RS-1.0 (NForce4, Skt 939).

Having trouble finding it on the Foxconn site, but there's a detailed review here.

[accat13]

is this the beast http://www.foxconnchannel.com/Produc...D=en-us0000020

I don't think the -5v issue seems to be the problem as it is not mentioned in the power supply section of the manual.....I stand to be corrected of course...

[Virtualbody1234]

Here is your board at the Foxconn site: http://www.foxconnchannel.com/en-us/...D=en-gb0000131

Here is a link to its users manual: http://www.foxconnchannel.com/en-us/...NF4K8AC-RS-1.0 Page 14 refers to power supply.

Here is a link to the datasheet for your Seasonic S12-430: http://www.seasonic.com/pdf/datasheet/01PC/S12.pdf

The motherboard doesn't appear to require the -5v as lynx mentioned.

But the motherboard manual does mention something about:
ATX 12v Power connector: PWR2 and AUX PEX PWR connector: J2A1

Do you have those connected?

[lynx]

Accat13 appears to be right, it looks like that board doesn't require -5V. The manual shows the connector (pin 18 on a 20-pin connector, pin 20 on a 24-pin connector) as NC. If you wanted you could verify that by removing the wire from the plug on your old PSU (it's the white wire) and trying that again.

I take it that you've tried the PSU in another machine. If not, now would be a good time to do so. Just put the machines back to back and swap the power connector from one mobo to the other. Unclip the extra 4 pins if necessary.

[Skillian]

Thanks so much for the replies and links guys, it's really appreciated. I've not tried the PSU with another machine - I've not really got one handy but I'll see what I can do over the weekend.

But the motherboard manual does mention something about:
ATX 12v Power connector: PWR2 and AUX PEX PWR connector: J2A1

Do you have those connected?

That J2A1 connector I do not have connected. To be honest I'm not sure what it is. I wish the manual showed me more where it is actually located - unfortunately I'm at work so not with the PC at the moment.

However I can't think of any obvious connectors on the motherboard that I had missed, nor any cables on the PSU that might connect to it. I should note that when using my old PSU that works, I had everything plugged in the same places as with this Seasonic.

[Skillian]

The J2A1 connector is a standard molex connector on the bottom right of the board. I did have it connected - unfortunately it is not the cause of my problems.

I've just tried shorting the 4th and 5th pins, and I get the same response - the fan spins for a second, then stops. This would seem to indicate to me this is a broken PSU.

Do you agree?

[tesco]

The J2A1 connector is a standard molex connector on the bottom right of the board. I did have it connected - unfortunately it is not the cause of my problems.

I've just tried shorting the 4th and 5th pins, and I get the same response - the fan spins for a second, then stops. This would seem to indicate to me this is a broken PSU.

Do you agree?

I agree but i'd still want to try it in another computer to make sure...
If it's not a psu problem and you get the same one again that would be kinda annoying.

[Skillian]

Yeah, that's my worry.

I'm gonna set up my old AthlonXP system on tomorrow or Saturday and see if it works in that.