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Thinkpad 25 (also T470, T480) assembly design flaw *small pics*

T25-Retro specific matters only
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dr_st
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Thinkpad 25 (also T470, T480) assembly design flaw *small pics*

#1 Post by dr_st » Sun Mar 10, 2019 6:40 am

Between the T460 and T470, Lenovo changed the bottom cover so that only two screws hold it at the front, rather than three as it was before. The middle screw is missing and there are only the two at the corners. The new design carries on to the Thinkpad 25 and T480 as well.

The bad thing about this change is that if any of the middle front clips are broken, the bottom cover and palmrest will not stay together well in that area. This was addressed by some reviewers, for example:
https://www.youtube.com/watch?v=KTLTjCVNg2I

The HMM shows how to correctly remove the bottom cover to avoid breaking the clips - you pop the middle clips (next to the battery), the side clips and the back clips, and the cover comes off like a clamshell. you never pop or pry at the front clips, and so they won't break.

Unfortunately, as I recently found after taking the bottom cover off to upgrade my Thinkpad 25 RAM, even if you don't break the clips, there is a chance that the cover will not close shut in that front middle area, and a visible gap will be left.

Here is how it looks (gap area circled):
Image

A similar thing was observed by a few redditors on the T480:
https://www.reddit.com/r/thinkpad/comme ... d_upgrade/

I tried taking the cover off and putting it back on a couple more times, thinking that I didn't latch correctly, but no matter what I did, the end result stayed the same - it actually looks snug before you snap all the back clips and tighten the screws, but after that, there is a visible gap. I double-checked that the clips are not broken (they are not), but it's possible that they have been bent a little bit (although I don't know how it would have happened, since it does not seem there is any stress on the front clip when the cover is removed according to instructions.

It seems that the palmrest plastic is warped around that area (maybe the bottom cover too), which leaves this gap. It's quite possible I did something wrong when taking the cover off, or putting it back on (although I was as careful as I could, and as I said - the clips are definitely not broken), but in the end the conclusion is thus:
  1. If it's so easy to warp/bend the plastic so as to end up with such a gap, even when carefully following the instructions - this is bad design.
  2. If the middle screw had been kept, like on the T460, this would be a non-issue, since the screw would have kept the cover tight. You can see how applying pressure to the place where the screw should have been eliminates the gap (left side - no pressure, right side - pressure applied):

Image
Thinkpad 25 (20K7), X1 Carbon (20HQ), Yoga 14 (20FY), T430s (IPS FHD + Classic Keyboard), X220 4291-4BG
X61 7673-V2V, T60 2007-QPG, T42 2373-F7G, X32 (IPS Screen), A31p w/ Ultrabay Numpad, A21m 2628-GXU

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Re: Thinkpad 25 (also T470, T480) assembly design flaw *small pics*

#2 Post by RealBlackStuff » Sun Mar 10, 2019 8:16 am

On the X240s there is a similar problem, with a small gap at the rear between palmrest/bottom remaining after reassembly, if you don't do it properly.
The solution I found: before mounting the bottom, stand the machine straight up, with the 'rear end' (with hinges) up,
Then put the bottom at an angle of about 30 degrees, roughly like this: |\ so that any 'clips' properly insert, then 'fold' the bottom all the way down until it fully touches and tighten the screws.

Haven't seen a T25/T470, so don't know if this helps at all.
Lovely day for a Guinness! (the Real Black Stuff). And pigs CAN fly!

dr_st
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Re: Thinkpad 25 (also T470, T480) assembly design flaw *small pics*

#3 Post by dr_st » Sun Mar 10, 2019 8:53 am

I suspected that maybe the clips didn't latch, and tried a very similar technique to what you described on subsequent reassemblies, but it does seem like they latch fine - it's either that they sit "too high" or don't grab as tight as the other clips.

Normally, if the clips don't latch, and the cover just sits "on top" of the clip, rather than being gripped by it, then it is very obvious when you press down on it, since the gap won't close (like it does in this case), and instead the plastic gets deformed as the clip resists being pushed down (and if you press too had, the clip will snap).

It's possible that the first time I closed it, the clips didn't latch properly, and were pushing against the palmrest, causing the plastic to deform (I only noticed the imperfection a day later)? It seems very unlikely that such a moderate level of stress for ~1 day can cause the plastic to become permanently warped, but who knows... Although I really doubt this is the case - the clips really do seem to grab almost automatically if you close the cover using the 'folding' method (which is the natural way if you follow the principle of reversing the disassembly).
Thinkpad 25 (20K7), X1 Carbon (20HQ), Yoga 14 (20FY), T430s (IPS FHD + Classic Keyboard), X220 4291-4BG
X61 7673-V2V, T60 2007-QPG, T42 2373-F7G, X32 (IPS Screen), A31p w/ Ultrabay Numpad, A21m 2628-GXU

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