The Mother Board

[templeLobe]

CPU = INTEL duo 1.8 ghz
MOTHERBOARD = Asus, P5N-MX
RAM = 1gb, single stick
HEATSINK = ?
OS = WinXP pro serv. pk 3
POWER SUPPLY = Allied 400w (ATX)
VIDEO CARD = onboard, INTEL
SOUND CARD = onboard
CASE = Antler TX312
OEM SYSTEM = home build

Hi Everybody

I have had a progressive problem over the past few months now and it has reached the stage where I think it may be the mobo at fault...

At present the PC won't boot into bios - nothing appears on the screen for very long and the keyboard is'nt picked up according to what is said on the screen
- sometimes I will get a continuous tone and other times I won't hear anything, the cpu fan sometimes will run slowly (when it does if i press restart it speeds up again as if it is going to boot, but doesn't) and at other times it runs at normal speed but still won't boot into bios screen or any screen -
- when the cpu fan fires up at a higher speed the screen will start but often this disappears or the screen develops white vertical stripes ??

I know, this looks bad... - let me tell you what has happened from the start...

about 3-4 months ago the pc made a continuous tone and would not boot up, just froze, but if you turned off the pc and started again the problem seemed to sort itself out; gradually this happened more and more; sometimes it would boot and other times not
- I looked up the beep codes which suggested (by having a continuous tone) I either had a short problem or something wasn't plugged in right (video card, ram etc) - so i checked everything was securely plugged in, had a look for anything at all that looked out of place - nothing, still had same problem...

I disconnected a wireless mouse and the tone stopped for a day and came back - the problem I have is that the tone doesn't always come on so it is hard to tell where the problem lies

- so i did a process of elimination - I unpluged devices from the mobo until the continuous tone stopped and it seemed that when i unplugged the the secondary HD the tone stopped and for a day or so the tone disappeared - problem solved...?

- no, it started again??

then i completly stripped down the pc and checked I had assembled the mobo correctly, set at correct height etc and rebuilt the pc again with the same components - turned on pc and back to square one, continuous tone - unplugged devices again until tone stopped,

... I reached a stage where there was nothing plugged into the mobo except the power/fans - expecting The bios screen to still work and it didn't come on - the fans turned but no bios: and yes sometimes i got the tone again (!!??) -

Should the bios screen appear when only the power (and monitor, of course) and fan/s are plugged in? - have i caused more damage here, do you think?

the scrren won't come on properly so no bios, no nothing didn't - and that's pretty much how it stands now - so what started as an occasional problem has now deteriorated to the point where only the cpu fan and case fans fire up with occasional screen shots

Ummm... if you can help me it would be sooooh appreciated, !

Thanks In Advance
temple-Lobe

[Karlsweldt]

This is your mobo model, correct?
Possible the larger electrolytic caps on the mobo are going bad. Look them over, if any show a domed top, excessive tilt or oozing, they are bad. More info at www.badcaps.net/ . The PSU (power supply) is not immune from this problem, also. Being only 400 watt rated, it may be marginal. See if you can borrow a known-good PSU of at least 500 watts to test with. Then too, the BIOS battery may be failing.. causing the BIOS settings in the CMOS memory to become corrupt. One of the first signs a battery is dying is the date and time wandering off. With memory installs, if using only one module, you need to mount that in the first-detected slot, typically Bank 0, Slot 0. With mobo designs having dual-channel memory, you may need two identical modules in the same color slots.
When replacing the BIOS battery, you will need to reset all BIOS pages to reflect the true setup. If using a wireless mouse/keyboard, ensure that the "legacy" feature for USB is enabled.
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F@H.. to solve mankind's maladies.. in our lifetimes!

[Copper]

check the CPU heatsink and fan, give it a good clean and reapply some firmal compound
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"Only two thing are infinite, the universe and human stupidity,and Im not sure about the former." Albert Einstein (1879 - 1955)

[templeLobe]

[evasive]

[templeLobe]

I'll try and get a psu with 500w

when i built the machine 400w was recommended to me for the no. of devices i wanted to use, but what you say makes sense - i'll give it a try in next couple of days and let you know what happens

Cheers,
temple-Lobe

[fussnfeathers]

http://www.extreme.outervision.com/psucalculatorlite.jsp

Use that tool, it'll help you figure out how much power you need.

Newegg has this calculator too, use both, then take an average. The first one is more detailed. You may have a rated 400 watt PSU, but given it's an off-brand, you're maybe getting 250 watts tops out of it, less under heavy load. Same type of rating system that stereo makers use. Advertise that little home theater as 1000 watts, then you find out it's 300 watts, with a 1000 watt peak. You might hit that once. Maybe.
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Mine go to 11

[templeLobe]

[Karlsweldt]

Read the label on the PSU. It shows a maximum output current of all voltages combined. But there is a limit on that power output, if you load one lead source more than allowed. The highest current draw is from the +3.3 volts and +5 volts. If you max out one source, then the other voltage sources may not provide the desired levels. The only easy way to measure current is with a parasitic type ammeter. They just get pressed to the wire, and show a fairly accurate current. A local auto store should have one. Amprobe is one of the better-known names in test meters, but there are others.

As to the total power needs of a system, you need to figure in the video card, CPU, fans, drives and other devices which are power-hungry. Your reference of less than 300 watts may be only for the video card, especially with higher-end models. I would not use less than a 550 watt PSU. You can use a more robust PSU, up to 750 watts or so. It will not "push" more power to the circuits, only provide what is needed.
An automotive engine may put out more than 350 horse-power, but you seldom use that full amount. Normally, only about 1/2 that is needed.
_________________
F@H.. to solve mankind's maladies.. in our lifetimes!

[bugninja]

Continuous tone could also be a failing fan that the BIOS is trying to monitor (like CPU fan). You mentioned strange fan speeds, that is why I bring this up. If your system doesn't detect a functioning system fan it may not boot to protect your hardware. But if the fan is failing and not totally dead that may explain the slow overall death of your PC and the random times it does want to start.
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Our lifestyles determine our death styles.