Monday, 4 November 2013

Your ZX has evolved!

It seems I am never quite happy with the placement of my ZX Evolution board. This time I have placed the ZXevo inside a Spectravideo case. Previously, I have already changed the SVI keyboard circuit into a ZX Spectrum keyboard matrix, so it was not too much work to connect it to the ZXevo. Also the RGB and Joystick connectors were ready so I did not have to make them anew. (Fortunately the connectors could also be squeezed through the openings so I did not need to resolder them.)

With that old attitude of "trying out gets the things done" without pre-planning and measuring too much, I found that the evo board seemed to fit nicely inside the case. There never was any question about depth and width, but the height was a bit worrying. The keyboard block is rather bulky, and the pictured configuration leaves very little room between the board and the keyboard circuitboard.

It sure looks messy. The boards are fixed into place with screws, and for these I drilled new holes directly through the bottom. The SVI case is well elevated so it does not matter much if the screws stick out slightly. The board inside is slightly raised with plastic pieces, as the existing screw holders might otherwise get in the way. Besides, there's a metallic nut in each of the holders, and it would be a pity if these created some unexpected contacts with the board circuits... So I also put some cardboard between the case and the board.

To get all the connectors visible from the backside, some more cutting would be required, but here at least the VGA and the SD card are useable. Also, If I want to use a better PS/2 Keyboard, it's within reach.

Here's some of the details:

1. The joystick connector. This fits nicely into the existing opening, and screws hold it in place. The board end is shared with the keyboard connector. I made that part to be two separate chunks, so that the joystick wiring does not hang around uncomfortably when separating the keyboard part from the case.

2. The RGB connector. It's a bit pointless to use the ZXevo with a stupid VGA monitor, so RGB is preferable. I had to carve the SVI "TV" opening a bit to make the DIN fit. Now it fits so snugly it does not even need screws really. The SD card can be seen to the right, sticking out from the opening.

3.The Reset switch. This is the one almost absolutely necessary thing to make when working with Evo if you don't want to connect a PS/2 PC keyboard (=boring). Without a separate reset switch (to Jumper 6) it's not really possible to get at the service screen again without pulling the plug! This is just a simple microswitch that sticks out from the Spectravideo power switch opening. I used a separate plastic piece screwed in place to the bottom to hold the microswitch in place.

Only the basic keys are connected here, as connecting all the cursor keys and function keys and such would require a bit different kind of thinking. There's a possibility of using some of the keys for the Evo jumpers (such as the reset above), as they do not interfere with the keyboard logic, but dismantling the keyboard block gets a bit tiresome after a few times so I did not take this route.


  1. Seems to fit pretty well indeed. Do the keys work fine and all?

  2. The keys do connect, but my approach requires some hard work and could have been done smoother. The existing connections on the key circuit board have been first cut. Then two tiny holes have been drilled from the underside for each key contact. The new wires travel in the underside, and connect to the existing contacts. So, I think making a totally new circuit board for the keys would be better for those who have the skill/facilities....