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Atom Colour board by unknown manufacturer

Posted: Fri Apr 27, 2018 8:40 am
by John Ferguson
Here are some photos of the snapper game and colour board obtained when I bought the Atom last year. The colour is much more vivid than shown in my photo. I am using a TV for display.

The person who sold the Atom had no idea that there was a colour board present.

John
20180427_091355_resized.jpg
20180427_091554_resized.jpg

Re: Atom Colour board by unknown manufacturer

Posted: Fri Apr 27, 2018 9:49 am
by hoglet
Hi John,

Thanks for posting about this.

We spotted one of these a couple of years ago, but never got very far with understanding it:
http://www.stardot.org.uk/forums/viewto ... 13#p121013

How does the board output it's video, i.e. does it connect to the existing modulator, or does it output a separate video signal?

It looks like it might share some circuitry with the Acorn PAL Encoder, which also uses the MC1496P balanced modulator/demodulator:
http://stardot.org.uk/mirrors/www.bbcdo ... er_cct.png

This is something I would be interested in trying to reverse-engineer the schematic of.

What's the chip in the top left corner?

Do you have any photos of the underside of the board?

Dave

Re: Atom Colour board by unknown manufacturer

Posted: Fri Apr 27, 2018 10:16 am
by John Ferguson
Hi Dave

Will get back with chip details and photo of the underside.

It’s a pity we can’t find out who made it. Maybe underneath there is more information.

John

Re: Atom Colour board by unknown manufacturer

Posted: Fri Apr 27, 2018 3:39 pm
by John Ferguson
Hi Dave

Through a switch the output from the colour board and original negative end connection of C2 go to the switch with the centre pole as the output to C2 connected to the modulator thus switching from black and white to colour and vice versa.

The chip at top left is 74LS221N.

John
20180427_161515_resized.jpg

Re: Atom Colour board by unknown manufacturer

Posted: Fri Apr 27, 2018 3:47 pm
by oss003
John,

I think it's wise to clean the solderside to find out if there are some bad connections.

Greetings
Kees

Re: Atom Colour board by unknown manufacturer

Posted: Fri Apr 27, 2018 4:46 pm
by hoglet
Hi John,

Sorry to be a real pain, but is there any chance of a better photo?

The one above is a bit blurred and the resolution is quite low, so it would not be easy to follow the tracks on it.

Maybe try to get a bit more light on the board, or use a tripod?

Dave

Re: Atom Colour board by unknown manufacturer

Posted: Fri Apr 27, 2018 7:19 pm
by John Ferguson
Hi Dave

I will use my camera tomorrow and clean the board to get a better photo.

John

Re: Atom Colour board by unknown manufacturer

Posted: Sat Apr 28, 2018 7:36 am
by 1024MAK
If your camera has a macro mode, that's even better.
Bright daylight is the best for taking photos of boards. If not, try using bright diffused lighting.

Mark

Re: Atom Colour board by unknown manufacturer

Posted: Sat Apr 28, 2018 12:12 pm
by John Ferguson
Hi Dave

Try these better photos. I hope they give you the information you need.

The red wire is the video output to C2.

John
Underside of colour board.jpg
Undedrside of the colour board
Top side of colour board.jpg
Top side of the colour board

Re: Atom Colour board by unknown manufacturer

Posted: Sat Apr 28, 2018 12:42 pm
by hoglet
Those look excellent John, many thanks.

Re: Atom Colour board by unknown manufacturer

Posted: Sat Apr 28, 2018 3:37 pm
by John Ferguson
Hi Dave

Is it your intention to create a working copy from the photos?

It would be a wonderful project if it is possible.

Some of the components like the green boxes are not known to me but most I imagine can be identified.

John

Re: Atom Colour board by unknown manufacturer

Posted: Sat Apr 28, 2018 4:36 pm
by hoglet
I was going to start just by trying to draw up the schematic on paper over the next week.

It's quite a complex design, and colour composite video is not the best format to use on a modern monitor (sRGB is). So I'm probably not going to actually make one.

Dave

Re: Atom Colour board by unknown manufacturer

Posted: Sat Apr 28, 2018 5:09 pm
by daveejhitchins
The little green boxes are inductors . . . But you (Dave) probably know that :wink:

There looks to be a lot of different transistors!!

Dave H :D