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Dissecting the first patient

A project log for Psioπ

Resurrecting a Psion Series 5 PDA with modern innards

rasmusbRasmusB 01/30/2015 at 18:240 Comments

Time to get to work!

As I wrote in the last log entry, I have two Psion units that I'm going to disasseble. One won't power up but is in good condition mechanically, and the other won't open but powers on correctly. I chose to start by taking the unit that wouldn't open apart. The goal was to at least extract the keyboard and learn something about the internal design.

I had already noticed some discoloration from leaking batteries in the battery compartment, but as I opened the unit closer I found out that it was worse than expected. The battery bay had cracked on the inside, and the leaking battery juices had crept up to the main circuit board. Oops.

Even the plastic had been attacked by the battery gunk. The metallized plastic (top of image) had been attacked to the point where the metal had dissolved completely.

Luckily, the circuit board itself seemed mostly unaffected though. In the lower left corner some corrosion can be seen on the exposed test points, but apart from that the board looks fine! From this point, getting the main board out was just a matter of removing three Philips screws and disconnecting the three FFC cables for the keyboard, LCD and speaker.

So this is what I have to work with. I have this crazy idea of keeping the CF bay intact, to be able to build some kind of expansion boards later on (using the CF connector with a custom pinout). That will of course depend on how compact I can make the new main board. The old board is 1mm thick and has 6 layers. Mechanically, it is a tigher fit than I had expected. The older Series 5 model had a daughter board installed, (see https://www.ifixit.com/Teardown/Psion+5+Teardown/1650 ) so I had expected some more room. I might be fooling myself though since it is very hard to estimate the amount of "air" inside the chassis.

Right now, I'm playing with the idea to make a cast of the inside of the chassis (using alginate or something similar) to find out the exact volume I can use. Ideas are appriciated :)

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