system fails to start

[tssatt]

I upgraded my mother's computer and it fails to do anything. I've built 12 systems over the past year and this is the only one to give me a problem. Her new system specs are as follows:
300W power supply
Asus A7V8X mobo
Athlon xp 2100+
256 of 2700ddr
Radeon 9000pro
Sound Blaster Live Value
Aopen 56k Softmodem
40gig WD Hard drive
52x Asus cd-rom
Generic floppy drive

It fails to turn on. The little green light on the mobo is on so the it's got power. The little red light on the mobo is off so the agp card is ok. I've tried switching the case panel connections around and still nothing. I've checked all the other connections and all the jumper settings and still nothing. This is the first time this mobo is used so the bios settings will all be factory defaults, so clearing cmos will do absolutely nothing. I'd be able to figure out any problem if it even started the post, but it won't even come on. Asus's website is no help, so here I am. Please help!!! (if you can)
Tssatt

[Whyzman]

Hello tssatt,

Welcome tohttp://www.pcguide.com/ubb/pcgubb.gif Forums!

You might want to try a barebones initial fire-up. Only RAM, Vid, Monitor, and keyboard. If it makes it through POST then add the floppy...one device at a time until you hit a snag.

Are the fans spinning up?

[tssatt]

Still nothing with only video, cpu and ram. And no the fans aren't spinning.
Any more ideas?

[Whyzman]

Is your CPU fan connected to the motherboard header?

No beeps...nada?

[gwallen4]

It might be something as simple as a bad front panel power switch. You could (carefully) momentarily short the power on pins on the MB to see if it fires up. Or just connect the reset switch wires to the power on pins and press the reset switch to see if it powers up.

Or it could be the motherboard or a bad PSU.

[Whyzman]

GW, do you know if the fans will spin up even if the CPU is faulty?

Have you tried this PSU in another box, so you know it's good?

[gwallen4]

Whyzman: I'm not sure what your question means, since the fans in this case are not spinning.

But yes, I'm pretty sure the fans would spin even with a bad CPU assuming that the MB was still okay.

[Budfred]

It sounds like it might be a good time to do the barebones test outside the case on a nonconductive surface (like a wood table) and see if you get anything. If you don't, that probably leaves a bad CPU, bad mobo, or bad power supply as the most likely problem.

Budfred

Edit:

As Whyzman is indicating, if you get no fans, the power supply is the most likely suspect.

Budfred again

[tssatt]

The power supply is ok. It used to be in my system before. I was already thinking of the front panel switch being faulty. I've already
got a couple of extra cases lying around so I'll connect a switch from one of them and try it. Oh, and motherboards will begin the post with a bad cpu or even without a cpu. It just won't get very far.

[Whyzman]

I would say you're headed in the right direction...

With a known good power supply and the board LED lit, it would appear power is definitely there for the taking.

If the fans would spin up, whether the CPU is good or not...it would seem there's an "ignition" problem...momentary case switch, wiring to it, or...whatever sensor there is on the MB that receives the momentary pulse causing it to "ignite" the board...spinning up the fans, at least.

And, as you say...the POST should at least begin if it's being electrically allowed to do so....

[no-mbr]

Are there any MB board jumpers to check? At least the "clear BIOS", is it on the right pins? Any "power-on lan or keyboard jumpers?"

Have unplugged and reseated the processor?

[gwallen4]

Oooh. Good idea about the clear bios jumper. I've heard of a new MB shipped with that jumper on the wrong pins. It wouldn't power on.

And by the way, it's not necessary to borrow a switch from another machine. The front panel 'power' and 'reset' switches are identical - both are momentary switches, that is they complete the connection only while they are pressed. So you could just move the wires from the reset switch over to the 'power switch' pins on the MB to see if that will work.

[Budfred]

We just recently had a thread from someone who discovered the problem with his system was that the mobo came with the CMOS jumper on the wrong pins, so apparently it does happen.

Budfred

[ZURKE]

Mine would not start with out the CPU fan plugged in and working.

[gopi_vs]

The mobo could be faulty. Try an alternate mobo.

[ZURKE]

Thanks Gopi_vs, I was just making a suggestion. :)

[Technotic]

I would suspect the power supply most of all. People have a tendancy to think of them as indestructable but I have seen them go out at the drop of a hat, or a PS. If you are not getting even fan spin even for a second or two that's a large mark on the cause side for that main power box being the culprit. I have seen them fry in all kinds of ways, new and old, well cared for burning out before the neglected, and the simple act of moving them from one system to another has more than once given me and any standing by a good "heart check" when then went out with a proverbial FLASH! BANG! SMALL MUSHROOM CLOUD! kindda show. Most go very quietly though, as if they keep quiet you won't notice they've quit their job on ya. Do you have a Volt-Ohm Meter? If so, set it to an appropriate DC volts range and insert the NEG (blk) tip into a BLK wire hole in a regular molex and the other lead (red) into either the RED or Yellow wire's hole and flick the switch. RED/BLK should read 5 VDC and the YLW/BLK combo should give a 12v DC reading. Anything way off of those perameters means something just ain,t right! Power it down and quickly throw it out the nearest window before it explodes! 8>) hehehe just kidding about the last part but it sure get's any non-techie's heart going for a few seconds if they are standing close by being an inocent bystander!