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Motherboard Or Power Or Something Else?


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10 replies to this topic

#1 Brian_the_Cat

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Posted 12 November 2005 - 02:09 PM

Hi all,

I'm a new boy to the forum but would be grateful for your help on a problem that has suddenly developed on my son's machine. I have some knowledge but not a lot (what's that they say about a little knowledge being a dangerous thing..)

Anyway the problem is as follows:
  • The system was bought from novatech in the UK about 4 years ago. It is 2000+ AMD processor on a K7SA5 motherboard running XP home.
  • All was fine at lunchtime.
  • When switching on this evening, the fans (graphics, CU, case, PSU) start, the power LED, HDD LED and CD LED all come on (and stay on) but nothing else happens. Normally there would be one beep and the system would start. Now no beep, nothing.
  • The power switch and Reset buttons now do nothing - need to switch off at the wall.
  • I've check some of the power leads and they seem to be sending out 12V and 5V OK.
My guess is that the system isn't even getting to the motherboard ROM to start up the selftests.

Could it be the PSU?
The Power Switch?
The Motherboard?
Any thing else?

Any pointers gratefully received.

I'm not keen to change the MB unless I have to as the PSU is only 300W and any newer stuff is likely to need that upgrading too - I might end up with the costs of nearly a whole new machine.

Thanks

Brian_the_Cat

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#2 dannyboy 950

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Posted 12 November 2005 - 02:50 PM

From the age of the mobo I would suspect the cmos battery failing.

You are not getting past post so i suspect the battery.

Other possibilities are bad/unseated memory or other hardware problems.

#3 Brian_the_Cat

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Posted 12 November 2005 - 02:53 PM

Thanks for the ideas.

I've removed the battery it is at 3.5V, I have also reseated all the cards and the memory. So it's not that .

Mind you, any idea what voltage should a CR2032 be?

Any other suggestions?

#4 dannyboy 950

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Posted 12 November 2005 - 03:57 PM

Hmmnnnn battery voltage is ok. Check the capistors make sure the tops are flat and not rounded.
Also look for leakage, brownish looking stuff. Does the HDD lite flicker indicateing HDD activity?

Something that sometimes works is leaveing the system shut down for awhile letting everything totaly cool off and the do a hard restart. Dunno why but it sometimes works.

Try booting into safe mode if no joy try a boot disk anything to see if boot can complete and load windows.

#5 acklan

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Posted 12 November 2005 - 10:11 PM

Have you tried a different monitor?
If nothing is coming up it is more than likely it's a hardware failure. The easiest thing to start with is to put a voltmeter to power supply and see that you has adequate power supply.
If that checks out , and you have 2 or more ram installed try one ram stick at a time to see if you have a bad stick. Normally you get a CMOS beep with a bad stick of ram, but it's easy and eliminaes the ram.
Last, which is only hard if you don't have a spare video card is, try another video card.
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#6 Brian_the_Cat

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Posted 13 November 2005 - 12:59 PM

Thanks for the suggestions, I've tried them all with no luck:

MoBo looks OK as far I can see, no bulges or leaks; cleared CMOS; stripped right down to just MoBo and memory; changed graphics cards. Nothing. Just lights up the busy light on the CD, HDD and Power LED, doesn't check the Floppy for boot which it normally would.

Finally got to the point of switching in a different MoBo from one of my other machines and same problem.

Then thought of a different plan and switched the wires for the power switch and the reset switch. This time I could at least power the system down using the reset switch (now the power switch). Switch back in the usual MoBO and then neither switch worked again :thumbsup:

Based on the fact that two Motherboards behave the same way I am coming to the view that it is the case, either the switches or the power supply.

Will probably get a new case, if that doesn't fix it then a new MoBo (needs upgrading anyway though I'd rather not spend the dosh).

Am still open to other ideas though.

Cheers

Brian_the_Cat

Edited by Brian_the_Cat, 13 November 2005 - 01:00 PM.


#7 legoman786

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Posted 13 November 2005 - 01:50 PM

It could be your power supply... You said that the 12v and 5v lines are ok. How about the lines for the mobo? Maybe the ground? I've had this problem before. Spent $500 (parts were expensive in '99) before realizing it was the power suply.

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#8 dannyboy 950

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Posted 13 November 2005 - 03:06 PM

Ya know when ya mentioned the switch wireing the ole light bulbwent on.

I have had a few mobo's that Ihad to switch wires on some of the cases.
Check carefully the color code and pinout in the mobo manual against the case switch circuitry. I had to switch the wires in one of the plugs on a K7S5A board

#9 pcnut

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Posted 13 November 2005 - 11:21 PM

This sounds like the problem I had a couple months ago. I came home from a weekend away and moved the mouse to bring my pc out of standby. Nothing happened. Tried restarting, still got nothing. Tried restarting again and thats when it dawned on me that it wasn't POSTing. I had just rebuilt this system with everything new except case, power supply, and drives 6 months before that. I figured it had to be either the mobo or the powersupply and was leaning towards the latter since it was the oldest (it was 3 yrs old and came with the case). Turns out that was it. Three days later with the new power supply in and it was good as new.

Hope this helps,
John

#10 Brian_the_Cat

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Posted 28 December 2005 - 05:40 AM

Thanks for the help guys and sorry for taking a while to update this thread. Went for a new case in the end and everything worked fine so I've put it down the the PSU.

#11 acklan

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Posted 28 December 2005 - 10:25 AM

Good deal. Thank you for posting the fix.
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