Acorn Atom Replica build

[PhilC]

@rubber_jonnie Not had a chance check on my Atom but google and stardom searches reveal 1 millihenry being the value.

[rubber_jonnie]

@rubber_jonnie Not had a chance check on my Atom but google and stardom searches reveal 1 millihenry being the value.

Ah cool, thanks.

[rubber_jonnie]

Cool, a load of parts I ordered for the Atom all arrived today:

IMG20260220130039.jpg

In theory it should be pretty much all the remaining parts I need for the base build of the board before I add the keyboard and start populating with ICs. Fingers crossed I can get some of this done over the weekend.

@PhilC I'm looking at the schematics and I think the resistor pack should be 4.7K, did you find out what it was by any chance?

[PhilC]

Cool, a load of parts I ordered for the Atom all arrived today:


IMG20260220130039.jpg


In theory it should be pretty much all the remaining parts I need for the base build of the board before I add the keyboard and start populating with ICs. Fingers crossed I can get some of this done over the weekend.

@PhilC I'm looking at the schematics and I think the resistor pack should be 4.7K, did you find out what it was by any chance?

Just checked my Atom and it doesn't have any resistor packs, just a whole load of 1/4 watt axial resistors.

[rubber_jonnie]

Cool, a load of parts I ordered for the Atom all arrived today:


IMG20260220130039.jpg


In theory it should be pretty much all the remaining parts I need for the base build of the board before I add the keyboard and start populating with ICs. Fingers crossed I can get some of this done over the weekend.

@PhilC I'm looking at the schematics and I think the resistor pack should be 4.7K, did you find out what it was by any chance?

Just checked my Atom and it doesn't have any resistor packs, just a whole load of 1/4 watt axial resistors.

Thanks.

I found the resistors on the original schematics and they're all 4.7k so that's what I've gone with.

[rubber_jonnie]

Well, it didn't take long to get the remaining parts installed:

IMG20260221105644.jpg

And I followed it with a quick power on smoke test.

No shorts and I've tested all the RAM and LS sockets and power is in the right place on all of them. The only large socket I tested for correct power was the CPU, but only because I know which pin it is on the 6502 and that was OK too.

I need to ID the remaining IC's and ROMs and check power is good on those too next.

[rubber_jonnie]

So, progress today:

IMG20260221143903.jpg

And I was about to get going on stripping this for the switches:

IMG20260221143848.jpg

Only whilst trying to unscrew the collar to change to a larger tip, the plastic support for the iron tip broke on the desolder gun....

I've fixed it (Hopefully) as I had my old spare gun left over for bits, but it's set me right back. Very annoying.

[rubber_jonnie]

So, a big day for the Atom today. Whilst I'm waiting on the other parts I need it's getting it's keyboard :)

I started off by finishing desoldering the BBC B keyboard and harvesting then cleaning the keys:

IMG20260222114852.jpg

And from there started installing them according to images online and the silkscreen on the board:

IMG20260222154023.jpg

It's very reminiscent of installing the keyboard on the OSIO 600D in that there are pin holes for the switches, but there is enough play for the switches to move around, so I spent a lot of time trying to get everything aligned as I went.

I finally finished and I think it looks great:

IMG20260222160133.jpg

Of course the BBC is missing some of the Atom keys, so I've done my best to replicate, however I had to use the function keys for Return, Repeat and both Shift keys, as the Atom doesn't use full size Shift and Return keys and Repeat is not a key on the BBC. I now have spare BBC B key switches too, which is always handy.

I quite like the look of the red function keys, I think it looks like a halfway house between the Atom and BBC :)

Rather brilliantly the whole BBC B space/stabiliser bar fitted exactly as it did on the BBC and works perfectly.

[PhilC]

Looking good Jon. Hope those other bits have come in handy too.

[rubber_jonnie]

Looking good Jon. Hope those other bits have come in handy too.

I haven't done anything with the video board yet but I've used all of the RAM and logic ICs you sent :)

On question though, with Regards to the ROMs (You sent me two but I've not tried to read them yet) do you know what images are available for the 27C512's that this board uses?