Introduction
I left the Electron Clone with Jafa Mode 7 MK2 PCB with a small list of corrections and extras for this update and I have also given a bit more thought to a form of case that doesn't involve as much work as the folded aluminium/painted case I made for first version.Version 1.2
This version of the PCB will be red along with a couple of optional boards for the USB socket(s) and a switch for a MRB.
The changes are listed below
1) Correcting the RGB red/green error on the SAA5050
2) Fixing U28 silkscreen to read 74LS260
3) Mode 7 - change IC types and labels for U59 and U62 - ALS versions.
4) Mode 7 - change R91 to a multi-turn preset.
5) Remove IC14 - not required.
6) Remove Links 10 to 13 - not required.
7) Add mounting hole near slot 0/1 - not reliant on slot mounting holes to fix PCB to base.
8) Added USB header (power only) to power Gotek drive.
9) Added labels on LK9 - A & F for ULA type.
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The Case
My original thought was to sandwich the PCB between two pieces of acrylic, it could have a range of colours even clear if you like the look of the PCB. I set about designing the top piece of acrylic using Inkscape on the PC but before long I found that Inkscape was just not reliable enough to use so after a look for a simple freeware 2d CAD package I settled on the EasyEda PCB layout designer. At first I thought it would be a bit too basic but the more I worked with it I realised that I shouldn't use acrylic just a silkscreened PCB.
My designs so far for the top and base, the PCB's will come drilled and milled so it's a simple matter of using stand offs to mount everything.
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My colour of choice is black but there are other possiblities, red, green, white, purple and these..
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Assembly
And running out of parts...
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A pause until parts arrive, sockets, capacitors, switch, keycaps etc.
Two new small PCB's added for this build, one for up to 4 USB power outlets and the other for the MRB switch.
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2 or 4 USB sockets.
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While rummaging through a box I came across this heatsink..then I recognised it's shape..its for the Electron ULA! so I'll use it on this build.
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And restart - enough parts have arrived that allowed me to populate the board and start testing.
After the careful switch on of previous boards I went all in this time and populated the board with just about all of the components and switched on...it worked sort of!! I got the start up display but the text had chunks missing..I thought probably a duff RAM chip and it was.
Next I tried Mode 7, I tuned the new pot and it brought in a sharp picture but with random horizontal lines the size of the cursor flicking across the screen. The problem turned out to be the 74LS32 chip in the Mode 7 circuit.
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A nice crisp picture, much better than the prototype v1.1. A noticable improvement with all the superfluous tracks, links and IC removed from the PCB.
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Testing the new addition of a USB power outlet.
Assembling the boards into the case
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I looked at two materials for the top and base, acrylic and PCB. Both worked out more or less the same cost so I decided to use the PCB as it was much easier to place the holes and to include legends.
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Placing the spacers and mounting the PSU, the main PCB, the speaker, the USB sockets and the MRB switch.
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Test fitting of the keyboard to the lid and the lid to the base. I notice I forgot the legends for the composite video and audio!
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The connectivity..
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Testing the fitment of cartridges and keycaps. Wiring is finished but the main board will have to come out again as there are few components yet to fit.
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Interim testing, I still have the RGBtoHDMI interface to fit.
Fitting the RGBtoHDMI
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Fitting the RGBtoHDMI took a bit of time as it involved selecting the correct spacer, button and LED heights.
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First switch on of the RGBtoHDMI converter and a quick re-calibration to get a perfect picture. The improvements made around the Mode 7/RGB area of the PCB has helped the RGBtoHDMI to generate a good quality output in all modes.
![](/ElectronCloneM7/s_31_Clone_v1_2.jpg)
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I allowed for two different depths for the MRB switch, moving it deeper into the case prevents it from protruding and it's still easily accessable to use - I was concerned the corner pillar would get in the way. A close up of the cartridge slots and HDMI controls.
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Running nice and smoothly..
What's left to do is to complete the fitting of the LM324 and a couple of capacitors on the main board, fit the new white keycaps and finally screw in all the mounting screws.
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That's the last of the components fitted, the LM324 quad op-amp and the capacitors. The PCB is now fully screwed to the base.
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Plugged back into the monitors for final test..just waiting on the keycaps and that will be it finished.
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Keycaps on.
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One original and three new Electrons.