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Problem with old PC, No display, system running. Help

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September 17, 2011 5:03:14 PM

I have an old PC with a 6 yr old P4 HT 3.0GHz processor and 3 yr old Asus mobo P5GC-MX-1333 with 1 GB DDR2 667 Ram. 2 days back, system wont startup.. On switching on, the display wont turn on, monitor standby led keeps blinking as if pc is in standby but the cpu fan and hdd is spinning, no beeps.. Tested the ram on another pc and its fine, tested with another PSU and still no display, cpu fan runs an no beep.. Monitor is working with my another AMD pc.. Took out the board from cabinet and ran it barebones with only keyboard, and monitor, no hdd, but still the problem exists.. the only thing is to suspect is the board or the processor, but i have no way to test those individually.. Today after I tried restarting the system several times repeatedly, once it beeped twice, the display showed BIOS corrupted and needs recovery and starting searching for floppy and cd drive.. so switched it off and connected cd drive, on reboot again no display, so held Alt+F2 on boot and after 2-3 tries, it again showed up and started recovery from support cd and told to reboot on completion. But on reboot, same prob, no display, no beep. Again after a few restarts, suddenly it showed the post screen after 3 days, but after checking ram and halt on cmos reset error, system froze... On restart, the same story.. After several restarts, sometimes it beeps twice..

Then I suspected a onboard video prob, and tried a VGA card as well as an Nvidia GPU but still nothing on either outputs..

WHat shud I do? Is my processor dead, making it sometimes to show up?? or is it a mobo problem.. please help!!
a c 113 B Homebuilt system
September 17, 2011 8:41:37 PM

You could simply have a failed contact between the CPU and heatsink, causing it to overheat.

That might be an inexpensive solution, and if nothing else would be a good idea after so many years of operation. Just remove the heatsink and clean both surfaces with a lint free cloth (coffee filters work well) and denatured alcohol. Then apply new thermal paste, following manufacturers instructions.

You can also inspect the motherboard for failed capacitors. You can find pictures here so you know what to look for:
http://www.badcaps.net/
September 18, 2011 5:06:33 AM

Proximon said:
You could simply have a failed contact between the CPU and heatsink, causing it to overheat.

That might be an inexpensive solution, and if nothing else would be a good idea after so many years of operation. Just remove the heatsink and clean both surfaces with a lint free cloth (coffee filters work well) and denatured alcohol. Then apply new thermal paste, following manufacturers instructions.

You can also inspect the motherboard for failed capacitors. You can find pictures here so you know what to look for:
http://www.badcaps.net/



I had tried everything I could with the processor.. cleaned all contacts on the flat side (since its a 775 and not the earlier pin type) applied thermal paste, took it out of socket and tried heating the processor with a bulb to dry moisture and get it heated, resetting everything.. but nothing works.. If it was a heating problem, it shud turn off after say atleast 1-2 mts when it heats up, now the only things remaining to do wud be to check the caps as you said, I had avoided that as this ASUS mobo was just 3 yrs old and the pc im writing from, has a 7 yr old ASUS mobo.. and also to check the pins of the socket as I had only cleaned the processor contacts.. Thank you for those tips, I must check it.. Also, Is there any chance that my processor blew out one fine morning?
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September 18, 2011 5:10:38 AM

HEy, badcaps states exactly the same probs I have!!

Motherboard fails to POST.
Memory Test Fails.
Fails to fully boot (or even install) Operating System.
System randomly and frequently freezes.
Random & frequent 'Blue Screens of Death'
BSoD or hard freeze under heavy drive activity (Either RAID, SCSI, or standard ATA)
CPU temps abnormally higher than usual under typical or less load.
*CPU VCORE & other system voltages are erratic or far out of tolerances.
Resetting the system after a freeze and the system will not repost."

Thanks for it!! gotto check now!!
a c 122 B Homebuilt system
September 18, 2011 5:20:43 AM

jj, it could also be the PSU.

The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

Make sure you plug the CPU power cable in. The system will not boot without it.

I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire (standby power supply): 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.

September 18, 2011 5:07:27 PM

hello jsc,

Thanks fo your detailed reply.

I am an electronic hobbyist and also do repair smps, so I have a spare working smps which Im using to run the secondary backup system from which Im writing now. I get the same result on powering up that board even with this perfect smps.. ALso checked line voltage the first day itself and all where fine on the main smps.

Tested RAM on cousin's pc and did a mem test and it was fine.

This mobo didnt have a buzzer and I had one connected 3 yrs back when I bought. It used to beep once normally, but now, no beeps.

I have no addon GPU, just the onboard GMA, so to isolate it, I tried with a PCI VGA card and still no display.

The only 2 things left to test are processor and mobo which I will do tomorrow if My cousin has the same socket as mine.


Also I would like to point out a tip in your troubleshooting guide which I really liked.
"A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch. "

With some experience in repairing SMPS, I would suggest not to turn on any PC smps without a load. There is a feedback circuitry in the smps which checks the output voltage and control the power output and voltage regulation. When there is no load, the output voltages will be higher, making the logic to think of an overvoltage and shut it down. So we might think PSU is faulty. Some cheap PSU's just blow off a controller chip, so in order to do that, please connect a mobo and a hdd so that atleast a 20w load is there on the psu to operate properly.
!