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Upgraded CPU on laptop, now screen won't work

By Maree · 8 replies
Aug 10, 2014
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  1. Hi, hope I've put enough specs in profile for you to help. I have a Compaq Presario 6735s I bought around 2008. CPU quite slow but graphics card not bad so made decision to upgrade. Looked up the laptop manual here to find compatible CPUs for motherboard, socket type etc. Went through 3 different (*****ic) buys before I found one that actually fitted.
    Now with everything reassembled, screen will flash up once upon powering on, then nothing. All usual lights come on, even my wireless connects, makes usual start up noises, fan, dvd drive etc ....
    Proceeded to take everything apart again, re-connected everything I tampered with. Even RAM, which I didn't have to remove before.
    Still same reaction starting up.

    Really frustrated with myself as thought this would be the right one. Could honestly cry, haha.

    I read the tutorial on here called 'No POST' to no avail either. I really hope it can come back from this.
    One last thing I can think of (before pulling new CPU out) is upgrading BIOS to support new CPU but with no screen I am stuck.

    Can someone please give me a little direction?
  2. Tmagic650

    Tmagic650 TS Ambassador Posts: 17,231   +234

    Did you re-install the old CPU to see if the laptop booted normally again? Upgrading CPU's on laptop motherboards can be a very difficult thing to do. What is supposed to be compatible in reality is not
  3. Maree

    Maree TS Member Topic Starter

    No I have not. That is what I fear. I am trying the upgrade bios by usb but have hit a snag again. Mine isn't fat16 compatible.

    See if I put the original cpu back in and (if all goes well) it boots up, I can do bios upgrade then? Then switch back to new one to see if it works?
  4. bazz2004

    bazz2004 TS Evangelist Posts: 1,585   +252

    If you've taken a laptop apart for the first time and got this far it's impressive. What would have been far better would have been to upgrade the hard drive to SSD. It makes an amazing difference to performance and is simple compared with your project.
  5. Tmagic650

    Tmagic650 TS Ambassador Posts: 17,231   +234

    It's a good idea...
  6. bazz2004

    bazz2004 TS Evangelist Posts: 1,585   +252

    This reminds me of when I bought a new motherboard and found that the CPU was not recognised. However, I did get an onscreen message about the processor not being recognised/compatible. Updating the bios was the way to go but being unable to get into Windows I was stuck. I ended up repairing the duff motherboard. I think that you should be getting a similar message onscreen so you need to try the original processor as already suggested.
  7. Maree

    Maree TS Member Topic Starter

    Ok, thanks guys. Bazz: I had no idea updating to SSD would have made a difference, are they expensive? I have been doing some troubleshooting last night and saw that it may be that I've warped the motherboard and have to re-solder or whatever but that's just way too far for me. Maybe if the screen was working I would see that message...

    Tmagic: I tried with a USB that is FAT16 compatible and it still didn't work, no beeping, nothing. I have to admit I'm getting really frustrated with all this.

    Thank you guys for taking time to help with this and I'm going to take your advice and replace CPU with original and see what happens, will keep you posted.
  8. bazz2004

    bazz2004 TS Evangelist Posts: 1,585   +252

    I've bought two SSDs in the last year. A 240Gb Crucial is currently around £70 and a 250Gb Samsung Evo around £85. Read the customer reviews on Amazon. Price will vary according to capacity but those are a useful size. I reinstalled Windows but I think there's software with some SSDs to clone your existing disc.

    Good luck with restoring the display. Maybe something is not connected properly. if replacing the processor doesn't do the trick you could try connecting an external monitor. There should certainly be signs of life apart from the lights being on when you press the on button.
  9. bazz2004

    bazz2004 TS Evangelist Posts: 1,585   +252

    When my laptop was dead after I'd worked on it I managed to get it going. Firstly, I removed the battery and power lead and then pressed the on button for 30secs. I reconnected the power cable and was able to boot it up as normal. I think there was a problem with static after I'd taken out the motherboard to repair and reassembled everything. I'd been so careful to get everything right that I was thinking of the surgical analogy "the operation was a complete success but unfortunately the patient died." It's a long shot but you never know.

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