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(Note: photo is of an Issue 1.0 Mainboard)
So this is my 'Electron Case' variant of an Acorn Atom computer, though you don't have to build into an Electron case.
Perhaps this is more a clone than a replica though ? It is functionally the same as an Atom, though I have made a few 'upgrades' to more available parts but tried to keep it in keeping with the original design:
the 24 2114 RAM ICs have been replaced by an 8K (video) and 32K RAM ('text' space)
the OS ROM is replaced by a 16K EPROM which has additional space for BASIC with Floating Point and DOS
the Utility ROM (e.g. for NFS) is replaced by a second 16K EPROM with links allowing selection from four different images (Issue V1.0 Boards have a 2732 fitted)
the YPrPb outputs have been beefed up with the addition of a video driver
the Alan Knowles screen noise eliminator has been incorporated
A complete replica Atom comprises three PCB's - a Mainboard, Keyboard and optionally a Floppy Disk Controller (FDC) Board.
The Replica Atom Mainboard will fit in an Electron Case in the space occupied originally by the Electron's mainboard, I managed to fit an Econet interface onto the board as well. The FDC Board fits where the Electron power supply board was and also includes a GOTEK.
There are three variants of keyboard, one that fits in the place of the Electron Keyboard, a second which is intended for a non-cased build (this will not fit in an Electron case) and a third which fits in an Atom case. The 'Electron' variant reuses the original Electron key switches (plus a few extra) , the second uses Cherry MX switches, so you don't need to scrap an Electron to build one of these ! The third keyboard uses BBC Computer key switches and can be fitted in an Atom case (please note this board is designed to accept the white Futaba switches, later types may not fit ?).
Here are a couple of pages with info on construction: