Saturday, July 9, 2011

Detour #1 - The HX-20

I'm trying to get started on my Retrochallenge 2011 entry. It's already July 9, and I've only got until July 31st to finish. However, I have stumbled over two hobby-oriented detours on my way to the work on the PX-8 disk drive. The first one? Rejuvenating my dear old Epson HX-20.

The HX-20 is widely regarded as the world's first notebook computer. Epson introduced the system in 1981, and I sold them in retail when they were released. Later, when working for Epson, I had the pleasure of being on the portable computer tech support team.

Back in '07, I received an HX-20 system, along with accessories, as a gift from Bill, a Retrobits listener. Since then, I have used the computer from time to time, but it was somewhat hobbled by an old and flaky NiCD battery pack. I replaced that battery with a 4 AA cell NiMH homebrew pack, but there were two things wrong with this. One, the charging dynamic on NiMH is different than NiCD, and I was never quite sure if I would smoke the NiMH and cause it to leak inside my HX-20. Second, the 4 AA pack was a weird fit and thus, an unsuitable replacement for the 4 sub-C cells that ships with the unit.

I considered buying 4 sub-C NiCD cells and making my own pack, but this gets complicated. The soldering and heat-shrink work is pretty exacting, especially since the 4 sub-C cell pack fits really, really tight in the HX-20's battery compartment. So, after some research, I found out that Batteries Plus makes custom batteries, and I gave them a try. The result was very good.

Here is the HX-20 disassembled, ready for the new pack. Disassembling the unit is pretty easy, but there are flat ribbon connector cables to worry about. These can be fragile and brittle in older computers, so I was quite careful in working with them.

Batteries Plus obtained and used the right connector type, so the battery fit snugly but perfectly. This is the battery they made:

Here it is installed, with the battery holder back in place:

The flat ribbon cables I mentioned before were a little tricky to get re-seated properly when I put the two halves of the computer back together. At first, some of the keys on the keyboard didn't work. I needed to take it back apart and re-seat those cables, then all was fine. Here's the unit back together, and running from the charge the battery had as delivered:

Happy me - 1981 computer, 2011 batteries. As you can see, the system itself is in great shape. I've got all the manuals and everything. So, in a little while, I'm going to crank out some new BASIC programs.

Next post - Detour #2 - my PC/XT clone Frankenstein!

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