Thinkpad 240x: A Risky Upgrade

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.

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.

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. 

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.

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.

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.

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...

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! 

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.

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.

Thinkpad 240x running a period appropriate copy of Windows 2000.

Resources:

- Thinkpad 240x Service Manual.

- Thinkpad 240 Service Manual.

- Thinkpad 240z internal RAM removal and 256MB sodimm upgrade.

- Thinkpad 240x Drivers and Utilities. 

Sega SC-3000

The Sega SC-3000 computer 

This is an interesting and rare machine. It is Sega's only computer. Originally launched in 1983, it predates the MSX standard, although it has comparable specs and game quality. Like the MSX machines, it is based on a Z80-compatible CPU, uses a TMS9929A (a version of the TMS9918A) video chip, and it has 16K video RAM. Curiously, it has very little RAM, only 2k. The Basic language is available as a cartridge that also adds more memory. The computer is compatible with Sega's first home console, the SG-1000.

My Sega SC-3000 after some superficial cleaning. This is a PAL version, I don't recognize the keyboard layout.

I got mine from a vintage computer vendor, it came with the Basic Level III B cartridge that adds 32K RAM. It did not come with a power supply, so I'll have to figure out how to power it.

Disassembly

The unit can be opened by removing 3 screws in the front of the case. Then the keyboard can be removed.  The top of the case is held in place by the keyboard and plastic tabs.

After removing 3 screws, the keyboard comes off. The top of the case is secured with tabs.

Close view of the keyboard connectors. I really dislike these kind of connectors. They are used in many other contemporary computers such as the SVI-328.

The motherboard is encased in a metal shield with top and bottom parts soldered to the motherboard. It is hard to remove the motherboard from the case: it is necessary first to desolder the on/off switch from two leads that connect it to the motherboard; there are slots in the bottom of the case, towards the back, were a flat screwdriver can be inserted to free the board from plastic clips, then the board can be removed, it is a tight fit.

To access the motherboard, I removed the top and bottom shields from the board by melting each solder point with a large iron tip, then bending the shield away from the board. After removing the shield, I used a vacuum desoldering gun to remove solder from the board and the shield tabs. I plan to mount the shield back in the motherboard but not solder it.

Motherboard, after removing the shield and cleaning some dust. There is a daughter board over the video processor. Amazing that the designers were able to route this single sided board.

View without the daughter board. The heatsink is quite impressive, I wonder what is under it ?

The motherboard is curious in that it is a single sided board. These kind of boards are more often found in VCRs, power supplies, and other high volume products. The only other computer in my collection that uses a single sided board is the Panasonic FS-A1, a later MSX-2 machine. 

This board was made in 1984, judging from the later dates on the chips.

The SC-3000 has 16K of video RAM, but instead of the common 4116 16k x 1bit DRAM Chips, it uses the MCM4517, also a 16k x 1bit DRAM, but one that only requires 5V, instead of (-5V, 5V, and 12V). Since only one voltage is required, the power circuit is quite simple.

View of the underside of the motherboard. The heatsink is for the 7805 linear voltage regulator mounted though a hole.

According to online sources, the power supply provides 9V and it is center negative. I verified the polarity, and it seems that the 9V are used as input to a 7805 linear regulator (mounted flat, on the back of the board, and attached to a heatsink through a hole in the board). The linear regulator generates the 5V needed by most components.

View of the video daughter board. The main IC is the LM1889N video modulator. It requires 12V that are generated here.

I used this opportunity to install my usual polarity reversal protection: a power diode, inline with the circuit, installed right after the power socket. The voltage drop from the diode should not pose a problem, because the 7805 will work well with an input voltage as low as 7V.

Trace cut between the fuse (large pads) and the power switch.

2-Amp diode installed for reverse polarity protection.

First Test

Now that I knew how to power the computer, it was time to test it. I also needed to get a composite video signal. The computer has a monitor port, I got it from there.

Setup for the initial test. I added a short adapter to reverse the polarity of a modern 12V power supply (central positive). I am using alligator clips (yellow and black) and a copper wire, to tap the composite video signal from the output din connector. I connected the Basic III-B cartridge. The red alligator clips are used in place of the power switch.

And it is working!

Resources

• Story of the SG-1000 and SC-3000 (Wikipedia).
• General Information about the SC-3000 at SegaRetro.
• Sega SC-3000 Review on YouTube.
• Sega SC-3000 30 Games in 3 minutes, on YouTube.
• Lots of Sega documentation.
• Sega SC-3000 Pinouts.
• Sega SC-3000 Schematics.

Macintosh Classic

I am a Mac user since about 1990. I remember compact Macs being very popular with the staff in college: It provided an easy to use standard GUI, desktop publishing, and campus wide networking, that was unmatched by PCs until latter in the 90's. Back then I had a 2nd hand Mac II, later I got a Powerbook 165c.

I generally don't recommend buying old Macintoshes from the late 80s and early 90s, because they are often very damaged with battery and capacitor corrosion.

First run.

But last Fall I saw a Macintosh Classic listed as broken and very cheap. One of the pics in the listing shows the video working and the desktop, so, it there is any problem with the computer, it is probably something minor.

A corner of another picture showed the included mouse and an upside down keyboard. The keyboard was an Apple Desktop Bus Keyboard originally sold with the Apple IIgs. This is my favorite Mac keyboard, and alone costs as much as the listing, and maybe 3 times more if it is the version with Alps switches. The space bar seemed of a yellower shade than the other keys, this is a characteristic of Alps keyboards so chances were high that it was the better one.

Keyboard with orange Alps mechanical switches. The space bar and case are ABS plastic that yellows with age. The other keys are PTB plastic. The keys share the early snow white design language used in the Apple IIc keyboard.

I got the Mac Classic, it is surprisingly smaller than what I remember, and, YES! the keyboard is indeed the "made in Japan" version with Alps switches! However, one of the keys broke during shipping. This is not a big deal as it can be glued.

Fixing the Keyboard

To fix the key I first removed the key stem that was stuck to the switch using a very small drill bit (a very small screw also works). I then carefully super-glued it back to the key, using metal wires (trimmed resistors or capacitor leads) to line up the stem and to reinforce the connection. I let the glue cure for 24-hours. Finally, I trimmed the metal leads flush, and I installed the key.

Fixing the Computer

Unfortunately, there was nothing to fix as the computer started with no problem and there were no signs of faults. Even the SCSI hard drive was working. I disassembled it, and the logic board looked very nice, no visible corrosion or capacitor leakage. I removed the lithium clock battery to prevent future corrosion.

Logic board and Ram daughter board. No leakage around the lithium battery.

Extreme care is necessary when servicing a compact Mac. There are high voltages that can kill you. Remember to properly discharge the CRT and power capacitors.

A few months latter, it stopped booting, showing instead the following sad mac screen on startup. The error code points to memory problems. 

Sad mac boot screen.

I disassembled the computer, and noticed some goo on the memory Simms. It was not there before. I cleaned it and that fixed the computer. I am puzzled about the origin of the goo. There are no electrolytic capacitors nearby. Maybe some capacitor in the analog board somehow expelled it ?

Mystery goo on the SIMMs and connector.

Booting after washing the goo and drying the board.

Replacing Capacitors

A month latter, after replacing the capacitors in a broken Mac Classic II, I decided it was time to recap this Mac Classic logic board too. It was a good idea, as I saw signs of dried leakage under some electrolytic capacitors.

I do have most of the SMD electrolytic capacitors required, but I decided to use thru hole capacitors instead because they are much easier to solder, and there is sufficient space to lay then horizontally on the board to secure then properly. 

Recapped logic board with thru-hole capacitors mounted horizontally. I added a drop of hot glue to further secure each capacitor in place.

Resources

• Check out these Adrian's Digital Basement videos to see what to expect when fixing old compact Macs.
• Mac Classic II Service Source.
• Sad Mac Error Codes.
• Repair Mac SE/30.
• Troubleshooting_Your_Macintosh_1992.
• Macintosh Upgrade and Repair Secrets.
• The Dead Mac Scrolls 1992.

An Amiga 600 from the UK

I got a non-working Amiga 600 from the UK. The computer looked to be in good physical condition, it included the mouse, power supply and some other cables. However the computer was listed as broken, it seemed to be one of those very frequent cases of "it was working years ago when I put it in storage, but it is not working now." 

Amiga-600 in very nice condition. The keyboard shows initial signs of yellowing. 

Repair

The most common problem with non-working Amiga 600 is capacitor failure. The SMD electrolytic capacitors used in 1990's electronics usually fail after near 30-years, and when they fail, they often leak corrosive fluid that destroys the motherboard by slowly corroding traces and even getting into integrated circuits and other components.

While I did not see signs of capacitor leakage in the motherboard, I proceeded to replace the SMD electrolytic capacitors.

Extreme care is necessary to remove these capacitor, because it is easy to lift pads and traces from the board. The best technique is to use hot-air to melt both terminals of the capacitor, then carefully lift it with tweezers. Another technique, that is faster but riskier, is to horizontally twist the capacitor with long nose pliers, avoiding puling on it, until it breaks, leaving behind its terminals still attached to the board.  The terminals can then be easily removed one at a time.

Replacement thru hole capacitors on the left of the board.

I did not have SMD electrolytic capacitor in my parts bin, so I used thru hole capacitors modified with some wire origami to match the SMD pads. This is a temporary measure while I wait for proper replacements to arrive in the mail.

Example of wire origami for fitting a thru hole capacitor to SMD pads.

My plan was replacing capacitors a few at a time, stopping in between to test the computer. 

After replacing the first batch, C612, C303, C304, on the left side, the computer came to live. I believe that capacitor C612, which is used in the reset circuit, was preventing the CPU from starting. There was also some leakage under it that I promptly cleaned with a Q-tip soaked with white vinegar (to neutralize the caustic liquid) and then with 91% Alcohol to clean the vinegar residue.

Microscope view of capacitor fluid visible after removing C612.

At this point, I stopped recapping with thru hole capacitors until the proper SMD capacitors arrive. There is no point in stressing the motherboard twice. These thru hole capacitors are not mechanically stable and may rip the pads if something bumps into them.

It is alive!

Keyboard Retrobrighting

While the computer was in very good conditions some keys were starting to yellow. I bleached those keys by sous-viding then in a plastic bag with regular Oxygen Peroxide (3%) at 70C (160F) degrees immersed in water. After a few hours, the keys looked much better. It is necessary to monitor this process to prevent over bleaching.

Contrary to what is often suggested, the retrobrighting process does not reverse plastic yellowing, it only bleaches it, and does not, in general, restore the exact original color. Still, it can make the computer look much better.

Floppy Emulator

Floppies are expensive and hard to find these days. I usually replace floppy drives with a floppy emulator such as the Gotek. Floppy emulators allow you to use a flash drive containing floppy image files directly in your old computer. Flash drives are so cheap and large that they can easily store all the software ever made for most old computers. The Gotek emulator is the most popular one and it is cheap, around 20 dollars for a basic model. I recommend flashing it with Keirf's FlashFloppy firmware that adds support for many more old computer image formats, and can be improved with hardware mods such as an OLED display, rotary buttons, speakers, etc. I like adding the OLED display, as it makes it easier to browse the floppy image files. Some folks sell modified versions of the Gotek hardware already flashed and with hardware mods. These sell for more than 40 dollars/euros depending on the vendor and hardware mods.

Homemade Gotek

A long time ago, I bought 2 Goteks that I modded and installed in my Amiga-500 and Atari 1040ST. Then I realized that I was going to need many more for all my old computers. I love open source hardware that I can assemble myself. So I looked for open source alternatives, and I saw that some enthusiasts had created versions of the Gotek PCB and had made designs freely available. The variant designed by Sundby is particularly nice: its size is under 100mm x 100mm meaning that it costs about 1 dollar per PCB to be professionally made; it adds support for 3-inch floppy connectors, as used in Amstrad computers; its mounting holes match the original Gotek; and it directly supports the OLED display, rotary button, and piezzo speaker mods. Furthermore, Sundby made his design available in EasyEDA.com so that it can be easily modified. When I first tried to order PCBs, some trace spacings violated manufacturing constraints of my PCB vendor, making it much more expensive to fabricate (over 20 dollars, instead of 5 for a batch of 5 PCBs). Thanks to Sundby's open design, I easily rerouted the PCB to correct the problem. 

If you are looking for a nice Gotek, consider buying directly from Sundby's website.

I used one of those PCBs to assemble a Gotek for the Amiga-600.

My version of Sundby's Enhanced Gotek. I rerouted the board to make it cheaper to manufacture. I am using some thru hole components (2 capacitors, crystal, and USB socket) instead of SMD to use parts I already had.

To mount the Gotek in the Amiga-600, I 3D printed a bracket and a display housing, both designed by CrazyBob and available on Thingiverse.

Gotek installed in place of floppy drive. I sanded and spray painted the 3D printed display housing to better match the Amiga.

Final Result: Better than new!

Resources

- Amiga 600 schematics

- Amiga 600 capacitor location

- Gotek schematics

- keirf FlashFloppy Wiki

- Sundby enhanced Gotek EasyEDA project.

- Sundby Web Site.

- CrazyBob Thingiverse Bracket for installing the Gotek in the A600.