PC runs properly only after CPU reinsert

Hi guys,
i have a strange problem with PC. After power loss, PC starts with absolutely no signal on LCD and it won't even beep. Just runs CPU fan, PSU fan, spins HDD, light up LED. But it won't show POST. Only thing which help, is to take off CPU and put it back into socket. But when I shut down PC, press PWR button, it starts again with black LCD and no beeps.
I have reinserted CMOS battery, changed CMOS battery, replugged power cord, changed PSU but nothong worked, only reseating CPU.
It happend me on about 5-6 completly different (new or old) PCs, on different places (if you suspect power plugs in house). It even happened to my friend, and i advised him to reseat CPU and it worked like a charm.

Can somebody please tell me what is going on? Thanx in advance.

P.S. There was one case that PC (with Pentium 4 for socket 775) successfully started after CPU reseating, but then it never worked again (only black screen, fans blowing, no beeps, HDD spining)
17 answers Last reply
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  1. Next time this happens and you need to re-seat the CPU, use Arctic Silver 5 thermal compound per established procedures. This will eliminate the thermal compound as the variable.

    It is quite possible that you and your friend got a bad batch of computers with poor CPU/heatsink installation. Something might have gone wrong on the production line.

    After doing this, if you still have problems, then treat the computer as a new build and follow trouble-shooting steps per this guide: http://www.tomshardware.com/forum/261145-31-perform-steps-posting-boot-video-problems

    Good luck!
  2. Ubrales thank you for reply.
    I always use new thermal compound. This also happened to me, while one my friend wanted to sell me his old PC. He was successfully using it for about 3 years. After i brought it home, it started with black screen (i didn't dissassembled the PC). I was wondering why it happened, CPU was correctly mounted. After reassembling, PC started fine (it was some kind of AMD Athlon 64).

    I was facing this problem with different variety of CPUs (Pentium 4 for 478, for 775, Core2Duo, AMD Athlon). I just got used to this problem, but i absolutely don't know what is causing it.
  3. From what you describe, it appears that it has something to do with the room in which the PC is operating. Are there any other devices such as electric heaters or other power hungry devices in the same room? Could it be possible that some power hungry (10 Amps, 1,000 Watts, or more) devices are turning on automatically and causing a power sag?

    A power sag is just as bad as a power surge, or a power spike. Sags, surges, and spikes are all bad. This could adversely affect the computer PSU and cause it to malfunction.

    Check the voltage at the plug outlets in the room. Next, carefully look for other devices connected to the same circuit breaker. Add up all the individual amps for all devices - lamps, TV, electric heater, PC, ceiling fans, etc. - then ensure that the total load is less than the capacity of the circuit breaker (15 Amps for most breakers, except kitchen, bath, garage).

    This will give you a clue as to what is really happening, and why.
  4. There is no other electric device in the room. Only one 4 plug splitter where are connected PC power cord, LCD power cord, router power adapter, speakers power adapter. I've got 2 cases with this ''black screen problem'' after city power loss. But other ''black screen'' cases happened in different city (e.g. friends PC, customers PC,...) without power failure, just from day to day. Nowhere is such a big power comsumtion. What about static electricity? Could it be this kind of culprit?
  5. In which geographic area do you live? More importantly, how clean and reliable is the power coming into the house?

    I live in the upper Midwest and we do have low indoor humidity and static problems, but there has not been any issues with any of our 3 desktops in 3 different rooms. Therefore, I don't think that it is a static electricity issue.
  6. is this geographic area so important? Mid Europe. I think the electo installation coming into house is reliable. I don't think this can cause problem. Do you have any HW solution idea?
  7. This sounds more and more like a incoming power issue common to the area in which you live in. The way to check the power is with an Oscilloscope, not a voltmeter.

    The re-installing the CPU may be just a coincidence and not related to the real issue.

    If you want a HW solution, install a UPS system. Here is a website to look into: http://www.apc.com/site/apc/index.cfm/ww/?
  8. it's strange. PC is dead, but as soon as i reinsert CPU, it runs just fine. I have an APC somewhere, but it has dead battery :(
    Tomorrow i try another Pentium 4, i got one left so i'll see what it will do.

    btw. today i bought from customer one old laptop Acer, which has completly the same problem as my PC. But this laptop runs only after RAM reseating, not CPU. Maybe i got computer flu virus in the air :)
  9. Very very strange indeed!

    Let me know how you make out.
  10. As soon as i figure it out, i'll post it here. Till that moment i only can solve this problem by reinserting CPU (that old Acer have something wrong with mobo).
    But thanks for helping anyway, i appreciate it :)
  11. Thank you! Your findings will certainly benefit us all.
  12. Hey! I got good news. After few testing (and lots of CPU reinsertions lol :D ) i finally find out where the problem was. The culprit was faulty graphic card. Good old GeForce 3 Ti just gone dead. Capacitors are like baloons so this is what was going on all the time. I changed new gfx card and now PC seems to run fine.

    The next PC i have with this black screen obviously has faulty gfx card too, but in this case it is integrated on board so i can't change it.

    Hope this will help someone :)
  13. Yes, good information!

    What threw me off was your statement in your first post "It happend me on about 5-6 completly different (new or old) PCs, on different places (if you suspect power plugs in house). It even happened to my friend, and i advised him to reseat CPU and it worked like a charm."

    Anyway, am glad that everything is fine now.
  14. maybe the failure of different components couses the same black screen. Faulty mobo, faulty gfx card, faulty CPU, faulty PSU. I believe all this components can cause black screen.
    Maybe i'm wrong, and this faulty graphic card was coinsidence, because friends PC works after reinsertion of CPU fine, without any problems. This is really weird.
    I recommend to check graphic card, mobo, PSU and CPU before saying you've got ghost in PC :)
  15. Agree!
  16. i'm bumping mostly because i have the same problem. my computer works fine then i reboot, and bam thing doesnt turn on until MULTIPLE cpu reseatings. like, i stream @ 1080p in bad company 2, all my temps are fine. by all rights, my computer is fine.

    something weird happens when it doesnt wanna post though, my cpu fan makes a weird whirring noise repeatably.
  17. hi, i'm sorry but i can't help you with that. I was facing this weird problem few more times since my last post. But i've never came up with solution :(
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