Intermittent boot, R51, no post and no display sometimes

[maxemm]

Hi. I have R51 which has a problem I simply cannot figure out. Sometimes it fails to boot at all-no beeps- fan and power light only. I noticed that flexing the system board or applying pressure at some point sometimes seem to fix this-until the laptop is moved-otherwise it can stay quite stable and works for hours if boot is successful. I was trying to figure out exactly where pressure needed to be applied and I think I have narrowed it down. There is some footage of a failed boot, and then a successful boot follows after applying pressure to the cooling fan unit on top of the CPU with little finger. Please see here (approx. 1 minute, 20 Mb. file): http://www.youtube.com/watch?v=4mUvdIjd6OM

It has been completely disassembled, system board inspected (top and underside) for loose connectors and etc., found no loose connectors, burns, coils, reseated cpu and memory chips. I'm not much of an electrician so I haven't tested for continuity on various parts or have any idea where to test This model does not have the Ati chip so I hope this is not the BGA issue many have mentioned suggesting a reflow is needed to fix this. (http://forum.thinkpads.com/viewtopic.php?t=57021)

So I'm thinking now maybe it's the CPU that is somehow loose, is there a possibility that there is a small fault on the board I simply cannot discern, and this small pressure helps reconnect a weak connection? Anyone have any ideas or experienced this same thing-anything?

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Original Specs-(currently only testing with ram card):
Product: ThinkPad R51 2887-32G [change]

Original description: P M 1.5GHz, 256MB RAM, 40GB HDD, 15 XGA(1024x768) TFT LCD, Intel Extreme, 24x24x24x/8x CD-RW/DVD, Intel 802.11b wireless(MPCI), Modem(CDC), 10/100 Ethernet(LOM), UltraNav, Secure Chip, 6 cell Li-Ion battery, WinXP Pro

[Harryc]

I would remove the fan and reseat the CPU. It is possible the CPU retention mechanism is loose as well. Use the hardware maintenance manual for removal procedures. Get some good thermal paste for the CPU too.
http://www-307.ibm.com/pc/support/site. ... 53169.html

[maxemm]

Will do that, thanks
Update: OK, tried removing cpu, cleaning-new paste on-no difference it seems- also it failed to boot again and previous pressure point used did not help unless this time holding underneath base of laptop-lower left corner so like trying to 'fold' system board-managed to start by holding the board with fingers like this but as soon as I let go laptop shut down. This time I put plastic of cotton swab underneath system board close to where PCMCIA slot was and pushed at same place as before-now running ok but problem still not solved, this flexing leaves me perplexed...

[kpbrouwers]

I have the exact same problem. Did you find a solution?

With the case opened up and the heat-sink/fan removed, I was able to determine that pushing on the processor (applying pressure) directly while turning on the power will get the system to boot. It then runs normally.

Reseating the processor with new thermal compound for the heat-sink had no effect. I would like to try replacing the processor to see if there is some internal connection issue, but I do not have access to a spare part right now.

Thanks for any input.


Kevin

[RealBlackStuff]

For both of you: the problem is with the Southbridge chip, which also uses BGA. When these solderballs become 'unstuck', then you get symptoms like yours.
Check the links in my signature, for more info.