Atom Colour board by unknown manufacturer

discussion of games, software, hardware & emulators relating to the Acorn Atom and Acorn System machines.
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John Ferguson
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Atom Colour board by unknown manufacturer

Post by John Ferguson » Fri Apr 27, 2018 8:40 am

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

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hoglet
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Re: Atom Colour board by unknown manufacturer

Post by hoglet » Fri Apr 27, 2018 9:49 am

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

John Ferguson
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Re: Atom Colour board by unknown manufacturer

Post by John Ferguson » Fri Apr 27, 2018 10:16 am

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

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Re: Atom Colour board by unknown manufacturer

Post by John Ferguson » Fri Apr 27, 2018 3:39 pm

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

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oss003
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Re: Atom Colour board by unknown manufacturer

Post by oss003 » Fri Apr 27, 2018 3:47 pm

John,

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

Greetings
Kees

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hoglet
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Re: Atom Colour board by unknown manufacturer

Post by hoglet » Fri Apr 27, 2018 4:46 pm

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

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Re: Atom Colour board by unknown manufacturer

Post by John Ferguson » Fri Apr 27, 2018 7:19 pm

Hi Dave

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

John

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1024MAK
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Re: Atom Colour board by unknown manufacturer

Post by 1024MAK » Sat Apr 28, 2018 7:36 am

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

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Re: Atom Colour board by unknown manufacturer

Post by John Ferguson » Sat Apr 28, 2018 12:12 pm

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

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hoglet
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Re: Atom Colour board by unknown manufacturer

Post by hoglet » Sat Apr 28, 2018 12:42 pm

Those look excellent John, many thanks.

John Ferguson
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Re: Atom Colour board by unknown manufacturer

Post by John Ferguson » Sat Apr 28, 2018 3:37 pm

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

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hoglet
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Re: Atom Colour board by unknown manufacturer

Post by hoglet » Sat Apr 28, 2018 4:36 pm

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

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Re: Atom Colour board by unknown manufacturer

Post by daveejhitchins » Sat Apr 28, 2018 5:09 pm

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
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ARA III, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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