Which is bad: Motherboard or RAM ?

[brandonkick]

I have a compaq desktop running windows 7.

It came with 2GB of DDR2 ram
500GB HDD
Integrated Graphics
DVD Burner


They brought it to me because after they "sprayed" it out with an air compressor it would no longer boot.

I instructed my brother to do this because he told me that the system was shutting down after a few min.

Overheating became my first instinct and I told him to check to make sure all case fans, heat sink fan and power
supply fans were running and that they were not dirty. He verified all fans to be running but some needed cleaned
and so did the heat sink. So he took an air compressor and sprayed out the computer cleaning everything including
the fans, heatsink and power supply of dust.

Afterwards he said the computer wouldn't boot at all. It would get to a point in the bios where it would freeze up
after checking the IDE devices and before checking the SATA devies.

At this point they brought the PC to me as I'm very experienced in computer repair.
My next thought was to reseat the memory, occasionally this does the trick.

Re seated memory did nothing for the problem.

I removed both sticks and inserted only one stick into slot 0. The system posted and ran fine for 20 min.

I shut the PC down, took same stick and put it in slot 1. The system posted and ran fine for 20 min.

I shut the PC down, set this stick aside, took the other stick and placed it in slot 0. System posted and ran fine for 20 min.

I shut the PC down, took this second stick and put it in slot 1. System posted and ran fine for 20 min.

I put both sticks of memory back in the PC. System posted and ran fine for 3 hours. I inserted my Hiren Boot CD and performed Memtest 86+ on the ram sticks for 13 hours. System ran fine.

I rebooted pc (both memory sticks still inserted) and left the machine sit idle while I went to work. I came home to the machine on the black bios screen stuck again between IDE drives and SATA drives check. Rebooted again same thing. Rebooted the third time and the system posted just fine.

So I decided to disconnect the HDD, DVD Drive, 56K PCI Modem card (meaning nothing but RAM, CPU working) and the system still did it with all of the various RAM stick/slot variations.

I installed another power supply and the system still did the same thing.

At this point I am sure it is either the motherboard or the memory but I can't be sure which it is.
I've had bad memory sticks that have tested fine on Memtest86+ (only one set but still). I really don't think this could be a
CPU issue and I know it's not a power supply issue.

I just dont know how to be sure (short of buying a new set of DDR2 memory sticks) which is bad?

I don't see any swelled caps on the mobo. But caps can be bad without swelling... I know that.


Any ideas/advice?

 

[alyoshka]

IMO, remove the CPU.....
Clean the TIM, the fan and the HSF yourself. Reapply a new coat of TIM and reseat the whole assembly carefully. Boot up the rig and check. In the BIOS settings, make sure your CPU power state is S1 or S3 or then Both. Make sure HDD's are not put to sleep and the rig is shutdown when idle. or absolutely powered down when in hibernation or sleep.
Give it a go and see if it all goes well, if not, you need to get the entire Mobo and stuff out of the rig and try it on a insulated surface, and see if it runs fine.
If it does, then you may need to add a insulating sheet behind the mobo before placing it back in the case.

 

[brandonkick]

I will clean the HSF and reapply new thermal compound but I don't think this is a heat issue....

The computer in question has now been on for going on 48 hours. It has been idle but still has been up for going on 2 days. Both sticks of memory (as well as all the parts that were installed when it was brought to me) are inserted.

I don't know what windows going idle would have to do with the computer failing to post. I know it's not a software (or hardware) issue as it displays the same symptoms even with the hard drive (and everything but the memory) removed. I'll check that as wel though.

As far as the CPU power states, I've never even heard of that (and I've been using a computer for 15 years, repairing them for going on 10). But again I will check and report what my BIOS says about the power states.

I don't see how this could be an electrical insulation issue as the computer has been up and running for two days now. I suppose it couldn't hurt to try though.

Personally I'm leaning towards it being an issue with the motherboard. It could still possibly be memory sticks but seeing as how they were memtest86 error free after 14 hours leads me to believe otherwise.


Thanks!

 

[alyoshka]

"As far as the CPU power states, I've never even heard of that (and I've been using a computer for 15 years, repairing them for going on 10)."
You mean you've never had problems with them and have never had to deal with those options... I think.

The insulation issue in my opinion could be a possibility because when you left the rig on unattended and came back, it wouldn't power back on, a leak building up over a period of no use but power state being on, definitely does that to a rig, and then takes time to get back to normal...
I rule out the memory as a cause of the problem, other stuff that I ruled out after I read your post have been, the PSU.
That leaves us only with the CPU and Mobo, that's the main reason I advised you to clean out the HSF assembly of the CPU, since I know when you reseat the CPU, you're bound to check it and see if it's pins/contacts look fine, plus that gives us an advantage of being sure about stuff like overheating etc etc.
If the CPU is fine, then something in the BIOS is not right or not being detected right, that not being detected right is mainly due to current interfering with the equipment, so the logical grounding and insulation advice.
The rig uses a maximum boost of current only during 2 instances, ones at the startup and second if when it wakes up. So the Sleep States are required to be checked in the BIOS.