Thinkpad 240x: A Risky Upgrade
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| Thinkpad 240x between a 14inch T60 and a 12inch Lenovo X61 tablet. The 240x is one of the smallest Thinkpads, with a 10.4inch screen. |
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| Profile view of the Thinkpad 240x. Very thin for a 1999 laptop. Great keyboard, better than any modern Macbook. |
The Thinkpad 240x is one of the smaller, and rarer, IBM Thinkpads ever released. It is the grandfather of the modern X1 Thinkpads and the X series.
I had one in the early 2000's that I had bought second hand from a Georgia Tech Student. It was my first Thinkpad. I used it extensively, I loved its portability. One summer, I took it as my only computing device in a long backpacking vacation across Eastern and Central Europe. I remember using it to remotely resolve technical issues at work from internet cafes, or from open WiFi networks. I sold it cheap to a colleague when I left to the US. I regret this sale.
Recently I saw one listed on eBay with a non outrageous price. I jumped on the chance, I made a reasonable bid, and I got it!
The computer arrived in excellent conditions. With the exception of the 3 horizontal lines on the LCD, everything looks great. There is some keyboard shininess, meaning the computer was well used. The outside is very nice. This computer does not have the mate rubbery finish of most Thinkpads. That finish degrades with age and scratches, and tends to become sticky, looking and feeling terrible. The finish on the 240X is glossy, and mine came scratch free. It is quite surprising that the original battery is still able to hold about 1h of power. The computer came with the original external floppy drive, and an aftermarket PCMCIA cdrom drive.
I think this is an excellent machine to run an old OS and interface with more vintage machines. While small, it has full size ports: VGA, USB (1.0), Parallel, and Serial. The serial port is nice to upload disk images to Apple II computers using ADT Pro, or to 8-bit Atari using an SIO2PC cable. The parallel port can be used to program old CPLD and FPGA chips using a simple cable.
This Thinkpad has a 500Mhz Pentium III. Enough to run anything up to Windows XP. It has a 12GB hardrive, that can be replaced by a modern compact flash or sdcard of higher capacity. Its main limitation is the small amount of RAM.
Dangerous RAM Upgrade
The chipset (82443MX) supports a maximum of only 256MB. The computer comes with 64MB soldered on the mainboard, and a single PC100 sodimm socket. This means that the maximum practical amount of RAM is 196MB (64MB + 128MB sodimm). If a 256MB sodimm is installed, the BIOS shows 256MB but the computer won't boot. Part of the sodimm is conflicting with the onboard memory. On the internet, there are mentions of a special 196MB sodimm, available only in Japan. Still, I found it impossible to obtain such specialized memory.
There is a risky alternative, first demonstrated on the Thinkpad 240z: Remove the internal RAM, so that it does not conflict with the sodimm.
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| View of the computer after removing the keyboard. The motherboard RAM chips are behind the single sodimm socket to the right. On the left we can see the modem mini-PCI card. |
The internal RAM chips are behind the sodimm socket. They are easily accessible once the keyboard is removed.
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| Close up of the RAM area. I tried to remove a sticker that was over the RAM, but it also remove the chip markings. I think there is enough space to remove the RAM, if I am careful. |
I saw that there is sufficient space, so I went about removing the RAM without disassembling the laptop.
The easiest way to remove the RAM is to use hot hair. I started by using aluminum adhesive tape to isolate the RAM chips. This is the kind of tape often used to repair HVAC vents. I find that aluminum tape is very effective for isolating the area, and avoiding damaging to the case or melting nearby components, such as the sodimm socket. The aluminum deflects the hot air, and works as a heat sink for plastics and components, limiting heat damage.
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| Aluminum tape protecting the case and nearby components from the hot air. |
I set the hot air temperature to ~380 degrees Celsius, and I started by slowly warming the whole area of the board. This reduces damage due to thermal expansion. After a while, I lowered the hot air gun closer to one of the ICs, and I focused the hot air to its legs, quickly cycling around its perimeter. I used a pick to softly tap the sides of the IC, so that it came off the moment that solder melted. Then I repeated the procedure on the next one, and so on.
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| Removed RAM chips. You can see one of the capacitors sticking to the legs of one IC. |
After removing the 4 ICs, I cleaned the whole area with IPA. I then noticed that 3 of the 4 decoupling capacitors had been blown away. I soldered then back.
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| This is where RAM used to live. A sodimm is now required for the computer to boot. I managed to damage one of the pads (left most chip). I'll have to add a botch wire if I ever solder the RAM back. |
Time to test the computer. I installed the 256MB sodimm and I turned it on...
Nothing showed on the screen, but the computer beeped once, then 3 times in sequence.
I tried the original 64MB sodimm that came with it, but the same think happened.
Great! I just destroyed the computer...
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| Computer with 256MB sodimm installed. The Thinkpad 240 series requires low density chips. This 256MB module has 8 RAM chips on each side. |
I calmed down, and inspected the work. I checked continuity on the terminals of the decoupling capacitors, and the multimeter beeped. I have a short! I removed all 4 RAM decoupling capacitors (they are no longer needed), but this did not fix the short.
I took the computer to the microscope and inspected the area in detail. I saw that solder on some of the pads of the removed RAM were touching. I took some desoldering braid and removed excess solder from the pads.
I put the 256MB sodimm back, and this time the computer started to boot. Victory!
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| Computer starting after fixing the short. |
Network Upgrade
The Thinkpad 240x does not have Ethernet or WiFi on board. It has a CardBus Slot (i.e. PCMCIA) that can be used to install a network card. I had an WiFi card in my old one. But now, I have a better option. The Thinkpad 240x has an internal modem installed in a mini-PCI slot. I don't think I will ever use a modem, so I can replaced it by an WiFi mini-PCI card. This frees the CardBus Slot for other uses.
I installed an Atheros WiFi card I had in my parts bin. It requires 2 antennas. Once I salvage some (from a broken T61 display I have somewhere, or from an old access point) I'll install then in the display housing.
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| Modem removed from mini-PCI slot, and an Atheros WiFi card ready to be installed in its place. |
Screen Repair
As you can see from the pictures, the LCD panel is slightly damaged, with a few permanent horizontal lines. I plan to eventually replace it, once I find a cheap enough replacement. I though of replacing the SVGA panel (800x600, usually a Hitachi TX26D32VC1CAA) by a XGA one. The Japanese 240z version has a XGA panel, however, it uses a different cable than the SGVA model, and I don't think I'll ever be able to get that cable. Thinkpads of this era use the cable to distinguish between LCD models. I have some experience replacing and upgrading panels on other Thinkpads, for example I've added a QXGA panel (2048x1520) first to a T43 and later a T60. Only starting around the time of the T60 did motherboards automatically detect the panel.
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| Thinkpad 240x running a period appropriate copy of Windows 2000. |
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