2021 Nov 23

For many years now, I've had an IBM ThinkPad 760XL sitting in my closet. It was
brought into my workplace to be recycled, and I snagged it to take home along
with some other old laptops. Recently, I decided to see what would need to be
done to get it running and get modern software on it.

The cosmetic condition of the laptop is a little rough. There are many scuffs
on the top cover that I don't know how to remove. The top cover has a slightly
rubbery texture, so I'm afraid a standard cleaner might make it sticky. On the
back is a plastic flap that covers IO ports, and it is cracked. I could repair
it with some superglue, but the whole thing is flimsy so I think I'd rather
just remove it. Other than that, the machine is in pretty good shape. There are
two obstacles keeping me from using it right now:

First, I have no power supply. When I got it, I was able to borrow a universal
power supply from my workplace, and I was able to verify that it worked. It was
even able to boot in to the copy of Windows 95 installed on its hard drive. So,
as long as nothing has changed (it has been stored in good conditions since
then,) it is still probably working and I know potential "invisible" problems
should not show up. All I need to do is find a replacement power supply.

Unfortunately, finding the correct power supply was not easy. The 760XL uses
a 4-pin hexagonal connecter rather than a modern ThinkPad barrel or rectangular
plug. I haven't been able to find a proper name for it, though some sellers of
universal laptop power supplies refer to it as the "4 hole toshiba tip." I had
considered buying one of these universal adapters, but the ThinkPad wiki says
that some of these adapters short the G and S pins to the power pins, which can
cause damage to the laptop or the adapter.

Luckily, I was able to find the service manual for the laptop, and I learned
some interesting things. First, I found that the 760XL, as well as the CD, ED,
LD, ELD, and XD models can actually accept two kinds of power supplies: the 20V
50W supply, and the 16V 35W supply. This is in spite of the fact that only 20V
2.5A is listed on the bottom of the laptop. Second, I found that the part number
for the 35W power supply for my region is 85G6705, which allowed me to search
for it on eBay (previous searches for "ThinkPad 760 charger" and other similar
variations yielded nothing.)

So, if you need a charger for you 760XL, know that:
1. It can accept voltages between 14.5V to 17V and 18V to 21V
2. The G and S pins are not required, and you should be careful about what
   they connect to. They might be shorted to positive or negative in official
   power supplies, but shorting them to the wrong thing could cause a problem.
3. There are two official adapters made by IBM, a 16V 35W supply, and a 20V 50W
   supply.

I will order the 35W supply and see if it works. In the mean time, I will need
to solve the other problem: a lack of permenant storage.

The 760XL originally came with either a 2 or 3GB HDD. When I first opened the
laptop, I was concerned that the internal drive would not be easy to replace,
since it appeared to use a proprietary connector. However, when I disassembled
the drive module and removed the tape, I found that inside was a standard 2.5"
IDE drive, with an adapter to whatever connector the ThinkPad has on its board.

I don't trust spinning disk drives, especially in laptops, so I decided to
remove the drive. Besides, I want to see if there is anything interesting on the
original drive later when I get the chance. To replace it, I decided to use a
compact flash card with a 16GB capacity. I just need to get an adapter, which I
can also order from eBay.

Finally, I want to make a note to any other 760 owners: there is a NiMH battery
inside the palmrest, next to the right speaker. This battery is notorious for
leaking and causing damage to the keyboard connector and controller logic. To
remove it, you'll need to remove the top cover, disconnect the keyboard, remove
the palm rest, and remove the keyboard card. The IBM service manual has
instructions for all of these. Luckily, my battery was only just starting to
leak, and in an area away from the card, so no damage occurred. If you have a
760 of any designation, and haven't removed the battery, I recommend you do that
as soon as you can, since the possibility for damage is very high.

Anyway, I look forward to seeing what I can do with this old machine. I'm not
very interested in running it the way it would have been run in 1997. Other
people are better at that and I don't have any memories from that time anyway.
Instead, I intend to install a recent version of NetBSD and try to get it on the
internet, though I don't know how I'll do that yet. Hopefully everything else is
still working on the machine and my next update will be a successful "all went
as planned," but I'm sure *something* interesting will happen along the way ;)