Thinkpads Forum

Just throwing some ideas around, regarding the removal/replacement of a soldered on CPU.
The laptop in question would be a 240, which in and of itself, is quite a challenge because of its small size.

Using a low wattage soldering iron seems a tedious and likely impossible way to go, probably cracking the board, while applying upward pressure on th CPU. Clean up would be very difficult as well.

My thought would be to very carefully ‘Dremel’ away the old CPU, leaving the pins sticking out of the top of the board. Assuming there is enough pin to grab on to, apply heat from the bottom while pulling each pin out from the top with a pair of needle nose pliers.

Sounds like a chore but it might work. I’d have to be sure that each and every pin hole is free from solder, a small drill bit in the “Dremel” should do the trick. Hopefully the pins on the new CPU will go through the board and leave a little ‘meat” for re-soldering. It will be very close work for sure!

Finally is it worth the time and effort?
Would a Mobile Pentium III 500 or 600Mhz be that much ‘better’ than a Celeron 400Mhz?
Will a Mobile Pentium III 500, 550 or a 600Mhz non speed-step even work in a regular 240 motherboard using the max 320 RAM?

Questions, questions…Any thoughts?

Tim S

Only have a few thoughts and really no suggestions...

- Cutting away the old part is a good idea for components which have only a few pins; i.e., 28 pin dual-inline (DIP) ICs for example. Not so sure how easy/effective that would be for a CPU.
- The motherboard is probably a muti-layer design, meaning that in addition to the top and bottom traces there's some buried in the middle.
- Using a "solder sucker" can remove the excess pin and solder at the same time.
- Dremeling the through-hole with a drill bit would not be recommended because you may remove the hole plating which electrically connects the top side to the bottom (or middle) layers.

I have seen soldering irons with a "head" which is a long narrow rectangle. You put it against the row of pins, and it heats (and hopefully melts) the solder on all of them at once. You then use a solder-sucker to remove the solder. You'll probably need to use it in several spots on each side of the CPU chip. A lot of work, but I think it's possible.

As for your second question, "is it worth the time and effort"... IMO, the answer is 'no'

Finally, I'm not even sure the motherboard voltage(s) for a Celeron 400 would be what's needed to run a PIII 500/550/600.

They're not pins, they're balls of solder. So assuming you do get it off safely, you'll end up with something as flat and pinless as those LGA Intel cpus. The step after that would be applying fresh solder balls (which you don't have).

The 240 CPU appears to soldered directly to the motherboard and while its hard to see, I think by way of pins. I have seen, on eBay, photos of P3 CPUs and some appear to have a second layer with those round attachment points. I don't think these are soldered onto a board but are a press fit in some kind of bracket. Hopefully a P3 with the second layer can be lifted off to reveal the pins.
But it's all conjecture at this point as I'm not yet convinced that this major undertaking is worth the effort!
Tim S

I suppose the root problem is, slowness of running.
Whilst a faster processor would help, the other
solder-free method is an OS upgrade: debian 3.1 *nix
runs well on my 366mHz 600e--and ran well on the 166mHz
760 prior to demise--so long as you avoid the
so-called "desktop environments" *nome and *DE.

and the price is right:-)

tim S,

I've actually taken a fried chip off one of my 240's just to see if it could be possible. I had several Mobile PIII's laying around but....they where the socketed variety. So I lifted a chip off it's daughter board and......not the same pin layout. The mobile socketed chips use sold bump to the socket conversion board.

Once I had the 240's pump off it's mooring..... it looked like I had made a mess. I used a heat gun to heat the bad chip slowly and *gently lifted it.

Even with very little disturbance I managed to smear a few of the solder bumps.

You can buy the solder balls in quantity and it requires a special flux that is an absolute part of the process. The flux acts like a glue to hold the ball in place. Place in oven and hope that you haven't lifted or floated any other chips. Cool slowly, don't warp the board.

Or you can buy a perfectly good 240X system board, which will fit with no modifications right in your 240's chassis. Then you will be limited to 192M of RAM. The "A" LCD is much better than the later "B" version. That is one improvement.

I run Arch Linux on one of mine using the Fluxbox window manager. I have Windows XP on the other. Watching streaming video will never be a strong suit of the 240. Once you discover one limitation another will appear.

Nothing is impossible, I think it is possible to replace the chip but you may make a few costly mistakes to finally get one good example. That is the price of admission......

Solder balls are not easy to work with, which pretty much ends the CPU switch for me.
I'm not a big fan of Linux, just a personal preference but I find the current offering of XP to be just fine.
In truth my 400Mhz 240 Celeron runs XP very well with 320Meg but because of the extra cache and speed, I was tossing around the PIII idea. Since I have been able to run DVDs at full screen or wide screen without a hiccup and it is perfect for travelling with internal wireless, I'll leave well enough alone!
But thanks to all for their input.
Tim S