No Video - Ram, CPU or Mobo?

By Roberto77 ยท 9 replies
Oct 14, 2005
  1. I just bought and replaced the CPU fan on one of our office computers because the old fan would occassionally get very noisy. I took of the old fan (for a 370 socket) latched on the new fan and plugged it in. When I powered up the computer the fan worked and the HD light came on temporarily but that was it no video! I connected another monitor that I know works and still the same thing. In an attempt to test the video I plugged in a keyboard and started up the computer. The lights on the keyboard blinked twice as usual but the number lock light never came on even though I left it on for a couple of minutes and the monitor was still blank. Could it be that something happened to the CPU in the fan replacement process? I was careful doing the replacement although I did have to push down a bit hard on the bar that comes through the fan to get it down far enough to latch.

    Is there any way I can determine if its the CPU, RAM, Mobo or something else without buying more RAM or another CPU an testing?
  2. kirock

    kirock TS Rookie Posts: 1,221

    Make sure all the connectors on the mobo are seated properly. Also check the video card that it's firmly seated too. Plug in mouse, keyboard and monitor to computer. If BIOS detects these missing it may very well stop on POST (power on self test) without activating video. If that doesn't work temporarily remove newly installed CPU fan. Allow to boot to windows (if possible). If it does then fan is bad or too tight and forcing pin connections open on CPU socket.
  3. Roberto77

    Roberto77 TS Rookie Topic Starter

    I checked all connectors, removed all other cards (the video is built on mobo) connected only the mouse, keyboard and monitor, took out CPU and RAM in installed again, plugged in go on, light on mobo on, HDD light on front goes on temporarily, lights blink twice on keyboard and that's it!

    Any other suggestions??!!
  4. Vigilante

    Vigilante TechSpot Paladin Posts: 1,666

    Odd indeed.
    If I'm not mistaken, the heatsink on a socket 370 has a cutout in the metal on the bottom. This cutout fits over the plastic part of the socket. If you had accidentally put the heatsink on backwards, this would make the heatsink not sit flush, and could overheat it quickly and burn out. So triple check that the heatsink and groove and all is sitting mirror flush on the CPU top.

    Also, you say the video is onboard, I guess I have to ask if there is a video card installed as well? Is that the ONLY video plug on the whole of the back of the case? Cause if there is another video card, it could outputting video to that.

    Leave the system on for a few minutes. Does the metal heatsink get warm at all? Or does it stay cold? If it stays cold even after a few minutes, the CPU could very well be dead.

    Also, do you get any beep codes or sounds?
  5. Tamste

    Tamste TS Rookie

    This very simular to my problem to my problem.

    Replaced CPU heatsink and fan, and had problems with starting ever since.
    Once the PC does start normal service is resumed. Currently I have to frig the PSU to start before I have a chance of getting it to run. Changed the PSU but no change.
  6. Roberto77

    Roberto77 TS Rookie Topic Starter

    Vigilante you are right I put the the heat sink/fan on backwords. The question I have is would the CPU overheat so fast that it wouldn't even boot up the first time? I tested the CPU without the fan and it gets hot almost immediately. Could it still be dead even though it's not cold? Also, the onboard video is the only video no card. No beep codes from the mobo when I power on either. I did pull out the RAM to test it and it did give the 2 or 3 (forget the exact number) beeps then. Is there any way to be sure the CPU is dead before spending the $ to buy another one?
  7. Vigilante

    Vigilante TechSpot Paladin Posts: 1,666

    If you get a beep code when there is no RAM, you should also get a beep code if there is no video. So your video is likely fine.
    As for the CPU, heating up can also just mean it's getting voltage from the mobo, and doesn't mean 100% that it's working. Really the only way to tell for sure is have another CPU to test with, or perhaps a POST probe reader card.

    You can try resetting the BIOS perhaps.

    Also, Socket 370 CPUs are not very common anymore, you aught to be able to find a used one at a PC shop somewhere for pretty cheap. I know we put out old Sock370 CPUs (like Celerons) out on the used table for maybe $15 bucks. Heck you could probably buy a whole used PC (using s370) for under $50. And just take the chip out.

    Lastly, a PC normally shuts itself off if the CPU overheats, but that is a function of the motherboard and BIOS. If you PC doesn't have such protection, the CPU is likely toast. Try calling around and find a cheap CPU to either test with or replace yours.

    Good luck!
  8. Roberto77

    Roberto77 TS Rookie Topic Starter

    Thanks for the advice. I'm afraid we'll have to spring for a used CPU and see what happens. On Ebay it's about $30. We have a 1 Ghz Pentium III chip model SL52R. As long as the replacement chip is a 1 Ghz Pentium III chip does it matter what model it is? I know some models have 512 Kb Cache instead of the 256 Kb on the SL52R.
  9. Vigilante

    Vigilante TechSpot Paladin Posts: 1,666

    I wouldn't think it matters. If it's the same speed and the same socket it should work. That kind of support is also up to BIOS. If it doesn't work, you can try updating the BIOS (of course you need a good CPU to do this in the first place :) )

    Be careful buying one off ebay, surely if it doesn't work, you won't be taking it back. Or it would be a hassle. Check your local pawn shops and Good Will and thrift stores, socket370 cpus may turn up somewhere.

    happy hunting
  10. mailpup

    mailpup TS Special Forces Posts: 7,182   +469

    BTW, it never came up in the thread but be sure to use a thermal compound between the heatsink and processor.
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