Saturday, 13 April 2013

Evolution I, Part I

My ZXEvo has evolved!

I have to say, I never was quite happy with the ZX Evolution inside a plain mini-ITX case. Sure, it made it easy to get the computer up and running. Yet at the same time it seemed plain wrong, looking too much like a modern computer. Also, part of the fun of having this kind of computers is to build stuff on your own, so off I went to create my own case.  I hope this is not the last Evo casing I'll ever do, so optimistically I call it the "Evolution I"

I was already interested about re-casing my Evo when I came across the Schneider EuroPC. (See earlier post) I was very impressed with the simple layout of the case. In fact, I initially hoped to fit the Evo motherboard inside it, and even took some steps towards this goal. Here I used a keyboard part from an Apple II extended keyboard, and not the original EuroPC keyboard. This way it would be possible to rewire the keyboard to work with the Sinclair connector.

ZXevolution inside the EuroPC case. Also, a portion of Apple Extended keyboard.
As it is, I got bored with this idea although I could see it would work. Yet the EuroPC case is oversized and it would take time to build the keyboard connections, which was not my interest this time. But I got enough inspiration from this to make my own case. 

I started hunting for a small keyboard that would be compatible with the ZXevo without any additional work. I got a very good one from a net auction so I could start from the scratch. I removed the top of the keyboard to help the keys protrude slightly higher. (The keys are low, lapstop-style)

The small PS/2 keyboard, cover off.
The new case is made from bits of plywood that happened to be around. The plywood is 9mm thick so I could not just simply make a keyboard-shaped hole as the keys are too low. I used an electric router to cut the needed two-level opening for the keyboard, but a similar result could be achieved with two layers of thinner plywood.

This turned out to be a bit more hardcore than I expected...

When the keyboard was in place I glued a couple of plywood pieces to keep it there. I dared not use the existing screwholes as there was only about 3mm left of the plywood thickness.

When starting to work on this case, I had a couple of aims: First, the case top should be easy to remove no matter what, to get easy access to the evo board. Secondly, I want to be able to dismantle the thing. Thirdly, the important parts have to stay intact. This explains why I've basically left the keyboard as an external keyboard, cable and all. I did not want to break it apart at this point.

I did not have specific proportions in mind, but I knew I'd like the computer be generous in size, so it would be not too difficult to make. I'd be happy with something Spectrum+3 sized.

The underside, I don't much care about how it looks like.
In the end I had to saw off pieces to make the board fit.
The sides are hand sawn from the same thickness of plywood, and sanded. I knew I probably would make a second version of the case bottom so I did not do very precise work. The bottom part of the case is simply a plywood with the motherboard and the power-stuff screwed on. I put some rubber pieces between the wood and the circuit boards, so that the solders do not touch the plywood. The evo board is positioned more to the right hand side of the computer, as the taller parts of the board are at the right, and they should not collide with the keyboard bottom.

The first version of the case bottom, from 9mm plywood
When it came to connecting the power between the ITX-thingamajig and the zxevo board, I first used the ATX-style 24-pin connector. The cables protruded too much so I removed them and used the  ZXevo Molex connector instead. This connector is sideways, problem removed. The POWER ON pin on the ATX has to be shorted to the ground for the power to work. After that it's just a matter of connecting the appropriate pins to the Molex connector.

The first version of the case turned out a bit taller than I hoped for, because I was playing it safe with the dimensions. Of course, there are old computers that are very tall, like the C64, but I wanted this to look good and be comfortable for the hands.

For the second version, I could take almost a centimeter of height out from the front by making the sides slightly lower and using a thinner (about 3mm thick) cardboard for the case bottom. The case bottom needs some rubber feet so in reality I did not win more than about 5mm I suppose. I also had to carve some parts out of the case top so that it would fit with the lower configuration I now have. Obviously many of the connectors on the board are now unusable, but I don't see a need for them.

The second version of the case bottom was made of a thin cardboard panel.
The bottom part dimensions are 40cm x 17cm, whereas the keyboard part is bigger, 44cm x 19cm. This gives an illusion of lightness, a trick inspired by the Sinclair QL case design. A straightforward box was another option, but it would be a bit more demanding to do with all the visible seams and joinery.

The new bottom is not so sturdy as the first one, because the cardboard is this crappy thing I took from the back of a photograph display. 3mm plywood would have been ideal, but there was none around at the moment. Hopefully the cardboard becomes more rigid when I build a backside from the 9mm plywood.

Playing it to the last millimeter with the power cables...
There's some things yet to do: The back panel with proper RGB and Atari-style Joystick connectors.  Also, rubber feet for the computer. (Some of the screws come through the bottom...) I'll also have to think how to connect the top and bottom parts of the case in a way that the top could still be easily removed. The case currently works so that the keyboard portion is simply placed on top of the sides, with nothing to join it. It's ok on the table but for moving around this is insufficient.

I hope to continue this project to its conclusion. See you later! (Check the Part Two)

Previewing the backside. The RGB is still directly connected to on-board pins.

1 comment:

  1. Whoa, another interesting case mod coming up :) I was thinking if velcro would be a handy way of connecting the keyboard to the case.