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Trying to fix a PC.... should I just give up?

Posted on 2009-04-07
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Last Modified: 2013-11-09
I have some elderly neighbors that I'm trying to help out.  They had a PC die on them.  

It was put together by a local clone shop.  It had an Asus A7N8X-X and an Athlon XP 2700+.

The thing just would not power up.  I tried it with a known good power supply and it still would not power up (the LED on the board would light up when power was connected).  I figured it was the motherboard so I got a A7N8X-LA off of ebay.  It's the same motherboard except smaller (same chipset and the like).  I plug the new board into the known good power supply and get no activity.  At this point, I figured that it was a bad CPU.  I borrowed a XP 2800+ from a friend with no positive results.  I tried the power switch jumper on all the control panel pins just in case, but still no love.  I thought there might be something wrong with the power switch, so I salvaged one out of another case with the same results.  

So basically, I have a new board, a working power supply, and a different CPU and can not get so much as a spinning fan.  I'm about ready to give up.  Anyone have any ideas before I tell them to bag it?

Thanks!
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Question by:Jared Luker
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Expert Comment

by:lovylove143
ID: 24093673
How can u figure out the exact problem.... When u start the pc it there any display on screen if no check for onboard display... try cleaning ram... or at last take to some good repair shop...
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Expert Comment

by:jamietoner
ID: 24093690
Try assembling the system outside of the case, could be a short when it's in the case.
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Author Comment

by:Jared Luker
ID: 24093691
I'm very experienced in the matters of PC repair... I was just looking for suggestions from other people that are likewise experienced.

Like I said... there is no power... no fans... no POST.  There is an LED on the old board when it's plugged in and no LED exists on the newer board.

I did change the CMOS clear jumper....
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Expert Comment

by:Lee W, MVP
ID: 24093716
Did you try different RAM?  In Different Slots?  ("known good" RAM is not good enough.  Asus boards, in my experience are NOT typically finicky, but I HAVE seen boards that are - finicky to the brand, or the speed of the RAM.
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Assisted Solution

by:alfredobinda
alfredobinda earned 125 total points
ID: 24093730
Did you happen to hear any tones out of the motherboard speaker when you tried to boot? These will usually clue you in to the source of the problem. I assume that there were no alarms since you did not mention them.

I assume then that either power is being interrupted before it can reach the BIOS (which means a bad board, these things happen even on new boards), or that the switch or its connection is faulty. If I think there is a problem with the switch, I usually use a small piece of wire (copper is best, but a paperclip may work) to short the power pins together. When trying this, PLEASE use only one hand so that you don't conduct the electricity across your chest.

Please post the results of this test or the tones if you hear them and we can move on.
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Expert Comment

by:alfredobinda
ID: 24093736
Sorry about the elementary explanations in my previous post, I hadn't refreshed to see that you are experienced in computer repair.
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Author Comment

by:Jared Luker
ID: 24093752
I actually have not had any ram in any of the slots during any of this.  I expect the machine to power up and give me a memory missing beep code, but this does not appear do anything to attempt to power on.  I did try it with the memory chips in once when I went through the trouble of mounting the board inside the case.

I did notice that when the power supply is plugged in, the BIOS chip gets warm, but there is no indication of booting anywhere.  

The old board has a spot for a PC Speaker jumper and it provides no sound.  The new board has a little speaker mounted to the board... no sound from it either.
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Assisted Solution

by:alfredobinda
alfredobinda earned 125 total points
ID: 24093766
Have you tried shorting the PWR pins yet?
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Author Comment

by:Jared Luker
ID: 24093788
I have not, but I figured that using two different real power switches (one from the original case and one from an older case I have) would have ruled out that possibility
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Assisted Solution

by:alfredobinda
alfredobinda earned 125 total points
ID: 24093815
It sounds like power is getting to the board due to the LED being lit (on the old board) and then BIOS chip getting warm.

Since there is no sound coming out of the system speaker, then I speculate that either the switch is not functioning correctly or the motherboard is faulty. If shorting the PWR pins does not work, then I would recommend trying a third motherboard (if it's worth it).

Short of that, I'm fresh out of ideas to save this system.
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Author Comment

by:Jared Luker
ID: 24093942
I'm inclined to think that the board is dead despite the second one being new.  I don't think I'll bother trying to get another board... time to get them to upgrade.
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Expert Comment

by:PCBONEZ
ID: 24094575
Some A7_ no post issues are resolved simply by clearing CMOS.
Not completely sure why.

Asus _7_ and to a lesser degree _8_ series motherboards are notorious for bad capacitors.
It's random about which specific models but many of them have problems.
Bad caps on Asus A7N8X-E
http://www.badcaps.net/forum/showpost.php?p=66416&postcount=1
Bloated Nichicon HM on A7N8X Deluxe
http://www.badcaps.net/forum/showpost.php?p=54211&postcount=1
Fujitsu Hybrid Polymers known to bloat on Asus A7 boards. (Poster repairs 100's of boards a year)
http://www.badcaps.net/forum/showpost.php?p=30168&postcount=7
Bloated Nichicon HM on A7N8X v1.04
http://www.badcaps.net/forum/showpost.php?p=49299&postcount=151

Usual suspects on these boards are.
Nichicon HM and HN series with date codes from 2001 thru 2004
Chemicon KZG series, can't handle heat, don't always bloat when bad
OST, don't always bloat when bad  
Fujitsu Hybrid Polymers, bright yellow with black markings, not true polymers
Misc el'cheapo brands that bloat.

Once you get over the phobia of replacing parts on a motherboard it isn't that hard to do caps.
Sourcing the correct kind of caps is moderately difficult until you know something about caps.
.
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by:snazy
ID: 24101288
Hi did not have time to double check on the specs of the motherboards, but you never mentioned video card? Is it integrated in the motherboard?
A PC would not start for four reasons only:
-motherboard
-processor
-video card
-memory
If the power supply is failing, it might still actually start and turn off in seconds, but there will be some boot activity
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Assisted Solution

by:snazy
snazy earned 150 total points
ID: 24101314
And by the way, if you connect the new motherboard, new cpu and new power supply at the same time, are they booting?(make sure there is video card at least there)
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Author Comment

by:Jared Luker
ID: 24101362
That board does have onboard video, but I also have a Radeon 9600.  But again, I would expect the board to power up and give me a no video beep code.  It never gets close to that point unfortunatly.  
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Expert Comment

by:PCBONEZ
ID: 24101495
When you have bad capacitors to the degree that CPU and RAM get bad/incorrect power then protective features will prevent it from booting.
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Bad caps in output of PSU can do the same thing as they are in parallel with some of the motherboard caps.
.

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Author Comment

by:Jared Luker
ID: 24101637
Visually, the caps look fine.  I don't have any way of knowing for sure if that's what is causing the board not to power up.
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Assisted Solution

by:snazy
snazy earned 150 total points
ID: 24101734
Is the fan starting at all?
If the motherboard and processor are ok, then the fan should start spinning and then you go to the point to get error code beeps for missing memory/video cards. Just note that some motherboards depending on BIOS dont produce sound. I got a incompatible memory for Asus motherboard once(wrong latency) and if it wasnt for the screen being connected to tell me that: "I overclocked", I would have no idea why the computer was not starting(the fan was starting though). Just went into BIOS and changed the settings for the SPD to manual and the latency to one the motherboard supports. Computers are sometimes more complicated than simple fitting of parts together. So connect the monitor if fan starts and watch for signs.
If the fan is not starting, then you have a motherboard, cpu, powersupply, power cable, electrical socket, power button issue. I narrowed it down, ha, ha.
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by:Jared Luker
ID: 24102677
lol... no fans... nothing!

No beeps or fans.  The cpu fan has an LED and it does not light up along with the fan not spinning.  Sometimes flipping the switch on the power supply would make the cpu fan LED blink and the fan nudge (showing that it would be spinning if it was working), but that's all it ever does.
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Accepted Solution

by:
PCBONEZ earned 225 total points
ID: 24102804
The fan spins when +12v is available to it.
It doesn't care is the CPU or the rest of the Mobo are okay.
If the CPU or Mobo are bad that can stop the fan by way of protective features turning the PSU back off but if that's the case you should at least see the fan 'kick' and then stop.

If there is no fan spin at all then you aren't getting +12v 'to' or 'thru' the motherboard at all.
Usual causes are bad power supply or shorted motherboard caps.
Unusual causes are +12v shorts in drives, video card, or motherboard MOSFETs,,, a burnt PSU to mobo connector,,, or a short [usually mobo] to the chassis.
There can also be grounds in other voltages that keep the PSU from coming on.

At this point I would borrow a known good PSU and see if it will start.

Also try with minimal system.
Disconnect everything from power and motherboard - except:
Keyboard, one RAM module, what's needed for video, CPU.
You should be able to get into the BIOS or to a 'no OS' type error if you have removed the problem device.
It is advisable to do this on a piece of cardboard on a table [build system without the case] to eliminate the possibility of chassis grounds causing the problem.
.
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Assisted Solution

by:snazy
snazy earned 150 total points
ID: 24106406
When the computer is connected to power,the power supply starts for a second and it first sends a signal to the cpu to check if it is ok to proceed. Which means that if the mobo or cpu are not functioning, no boot will happen and the power supply fan might or might not spin.
Dying power supply will more likely have enough left to spin its fan and wake up the cpu.
In this case it does not start at all, so fault is more likely cpu, motherboard,
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Assisted Solution

by:PCBONEZ
PCBONEZ earned 225 total points
ID: 24107452
That's not how it works.
-
Power on PSU and chipset (by way of +5vsb) begins continuously resetting CPU.
Voltage has ~50 milliseconds to be within ~80% of nominal. [Varies by ATX spec.]
If it's not there in time the PSU shuts back down. [This is a safety feature. No power to bad mobo.]
If it is there in time the 'Power Good' signal is issued and PSU stays running.
Now is when fans start.
Now is when chipset stops resetting CPU and the POST begins.
[ALL of that happens in <50 milliseconds.]

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Expert Comment

by:snazy
ID: 24107638
Well, thanks, better explained by you, but still the same as what I was trying to say :)
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Author Comment

by:Jared Luker
ID: 24107767
Thanks PCBONEZ... you seem to know your stuff!

I tried three different power supplies.  One of them I took over to another computer and it powered it right up so I know it's good.

I'm just going to send the new motherboard back and explore NEW options... :)
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Expert Comment

by:PCBONEZ
ID: 24107950
Motherboards and power supplies are just my 'thing'.
I buy broken ones just to see if I can fix them.
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Author Comment

by:Jared Luker
ID: 24107959
Lol... in that case, I have a couple for sale! :)
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Author Closing Comment

by:Jared Luker
ID: 31567866
Thanks guys
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