PC turns off randomly after I cleaned it thoroughly

The problem:

System keeps turning off randomly after I reassembled it! Had taken it apart to clean it up with an air blower.

The System:

AMD Phenom II X3 720 BE
ECS A790GXM-AD3 (Socket AM3)
Corsair XMS3 DDR3 1333Mhz 4GB Twinkit
HIS Radeon HD 5770 1GB
WD Caviar Green 640GB
CM690 with three stock fans
GlacialTech F101 CPU Cooler
NoiseBlocker 120mm 2000rpm fan x 2 (on CPU cooler)
NoiseBlocker 140mm 1600rpm fan (exhaust top back CM690)
Stock 120mm CM690 fans on front, side, and rear.
GlacialTech 120mm 900rpm cooler fan being used as a secondary front fan

The Story:

Okay so I'm facing a rather weird problem. I did a thorough cleanup of my desktop which had gathered a lot of dust. I took apart everything from the motherboard, GPU, CPU, Cooler to all the components of the CM690 chassis and used a high pressure air blower to clean everything up! That's pretty much the routine maintenance I do every couple of months.

I also added three new case fans to my CM690 (to work along the stock fans). All three are from Noise Blocker. One is 140mm while the other two were 120mm.

I decided to install the two new 120mm fans on my GlacialTech F101 CPU Cooler and use the stock 120mm fan that came with it as a case fan. So attached the new fans to the cooler rather comfortably and then reassembled my PC. I did have a gut feeling that I may not have applied the the thermal compound correctly because my right hand was shaking too much after prolonged use of that powerful air blower.

Anyways, I assembled everything back like normal and turned on the PC to find that my motherboard's CMOS had been reset. So I go into the BIOS and start to to reconfigure everything when suddenly, the PC turns off. I tried again a couple of times but I couldn't even get it to power on. So I reinserted the RAM modules. The PC did power on now but again shut down when I was about to login into Windows 7.

So then, to trace out the issue, I started taking components out to see what was causing the issue. I removed my discrete HD 5770 and connected the monitor to the integrated HD 3300 on my motherboard. But the system still had the same issue although I was able to get much deep in the OS (was just about to launch coretemp to check if something was overheating).

I tried using one memory module at a time in different slots but that didn't help as well. I disconnected all the fans except one of the CPU cooler's and another on the back of CM690 to see if the fans were somehow causing the issue but the problem still remains.

Now I don't have spare components to try and see what's actually causing the problem and I don't have warranty remaining on anything as well because it has expired on some stuff and void on others due to overclocking.

Can the Issue be related to the power supply? It would be really helpful if someone here can tell me what's wrong with my system because I've given up after trying for hours and am considering throwing away my Computer Engineering degree.

P.S. Sorry if I made any typos cuz I'm posting this from a mobile phone.
7 answers Last reply
More about turns randomly cleaned thoroughly
  1. Maybe you damaged something from too much air pressure?? Did you disconnect the fans before blowing them out? when you make a fan spin it can generate voltage and fry things. It's a long shot but maybe some dust got blown into the power button?

    I think what you need to do is pull the PSU and motherboard out of the case. Now with all that out of the case, plug in the PSU, mainboard with CPU and fan, 1 ram module and nothing else. Power it on by bridging the power switch contacts with a screwdriver. Make sure the PSU and cpu fans are spinning. See how that goes. If that still fails I would start by swapping out the PSU. If its ok, you may have something shorting out in your case.
  2. Did you remove the CPU heatsink and clean and reapply the thermal interface material? The CPU's thermal protection may be kicking in to prevent damage to the CPU.
  3. Look for something simple. ko's idea is very good.

    After that, if the system still doesn't work ...

    Work through our standard checklist and troubleshooting thread:
    I mean work through, not just read over it.

    Breadboard - that will isolate any kind of case problem you might have.

    Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. You do have a case speaker installed, right? If not, you really, really need one. If your case or motherboard didn't come with a system speaker, you can buy one here:

    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:
    At this point, you can sort of check the PSU. Try to borrow a known good PSU. 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: 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.

    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 or long single beeps indicate a problem with the memory.

    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.

    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.
  4. I'm actually able to POST and even get into the OS occasionally. The system just turns off randomly. I've even removed the case POWER buttons and LEDs but the problem is still there.

    If the PSU is faulty, is it possible that it would act normally when the system boots up but trip randomly? Though the power button LED on the back of the PSU is always on!
  5. Maybe too much 12V drain with the extra fans?
  6. Thought so too! Turns out that the PSU is okay because I was getting the same issues with a 620W Corsair PSU.

    Also turns out that the turning off isn't all that random. After some testing I noticed a pattern that it is dependant on the heat of the system.

    So I reapplied the thermal compound just in case. The CPU temperature in the BIOS stays constant at 40 degrees whether I underclock it to 1.6GHz or overclock all the way to 3.4GHz. It doesn't change even if the cooler fans are running at 900rpm or 2000rpm.

    I'm guessing there is some issue with the reporting of the CPU temperature but the CPU Cooler's heatsink, the northbridge, southbridge and GPU heatsinks aren't hot even when the system is running. However two other ICs on the motherboard get so hot that touching them might even burn the finger. One is the BIOS chip and I'm guessing the other handles the Audio cuz its near the audio ports.

    Now I don't know if these two ICs are supposed to get that hot but capacitors around the processor socket and around the 24pin connector are relatively much cooler.

    Is it possible that those ICs might be shutting down the system to prevent them from overheating? If so any idea what might be causing them to overheat in the first place?

    I really don't want to (and can't afford) a new motherboard right now.
  7. so, have you removed the motherboard and tested it outside the case with bare minimum config yet?? I hate to say it, but it does sound like a motherboard fault, maybe static has damaged it, or like I said before, when you cleaned it and had any of the fans plugged in making them spin, they can put voltage back through the motherboard and fry things.
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