Atom mystery photos

discussion of games, software, hardware & emulators relating to the Acorn Atom and Acorn System machines.
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jms2
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Atom mystery photos

Post by jms2 » Thu Oct 03, 2013 9:22 pm

I've recently joined the growing ranks of Atom owners on here - thanks Roland! :D

I'm trying to understand what add-ons are fitted to this machine. There seems to be some kind of 32k ram/rom card fitted, and its a Dutch one, but it doesn't resemble any of those on acornatom.nl. Here are some pictures. Does anyone recognise it?
P1030691.JPG
P1030695.JPG
And there was also this. It had fallen out so I am not certain where it is meant to plug in. It doesn't fit perfectly anywhere - there are always some pins which don't fit into any of the sockets.
P1030688.JPG
P1030690.JPG
Finally, why are the 6502 and the 8255 fitted into turned pin sockets which are then, in turn, fitted into the normal motherboard sockets? What advantage would this give?
P1030692.JPG
Thanks in advice for any advice!
John

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Re: Atom mystery photos

Post by jms2 » Thu Oct 03, 2013 9:33 pm

I should add - the ram slots on the right hand side of the machine are completely empty. It seems likely the handmade board fits in here somehow. But I can't see exactly how it fits in!
P1030694.JPG

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Re: Atom mystery photos

Post by CMcDougall » Thu Oct 03, 2013 10:35 pm

http://www.stardot.org.uk/forums/viewto ... 151#p71678
http://www.stardot.org.uk/forums/viewto ... 780#p71681
jms2 wrote:Finally, why are the 6502 and the 8255 fitted into turned pin sockets which are then, in turn, fitted into the normal motherboard sockets? What advantage would this give?
they are like that, so if the pins break, who cares! just put chip in another new turned pin socket, so hence won't have to 'try' and solder on a new leg to actual chip! 8)

I've also got 'homebrew' boards in mine, check the 'Recvd today' thread Saturday gone. Mine also had a board fallen out, but an educated guess and....

Just got mine on at the moment, after trying to get a proper D plug fast (£6 :shock: Maplin DC Power Plug 2.5mm / 5.0mm. Code: L49AY), so just soldered on a normal socket on a wire hanging out, so no pressure on motherboard, plugged into 5v from master compact PSU/Disc box, and, wait for it :
Image
:mrgreen:

also check the keyboard/solder side of the motherboard, as you may have two battery's ready to kill your Atom : https://fbcdn-sphotos-h-a.akamaihd.net/ ... 9631_n.jpg

Happy cleaning =D>

are all Atom case's bottom half really bad for yellowing?? just can't get mine as nice as top :?
https://scontent-a-cdg.xx.fbcdn.net/hph ... 3046_n.jpg
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Re: Atom mystery photos

Post by jms2 » Fri Oct 04, 2013 6:24 am

Thanks for the advice Colin - my Atom looks a lot like yours did prior to cleaning. It has a joystick port front left side like yours, and also the mysterious switch on the back and lots of orange wiring inside. But my 32k board "32kraam" is not the same as yours.

These two machines must surely have shared the same owner I think!

I will let you know about the case when I have cleaned it.

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Re: Atom mystery photos

Post by Prime » Fri Oct 04, 2013 9:23 am

The second board that had fallen out looks to me like a video RAM replacement board, it has an 8K SRAM on it.

At a guess I would say it probably connects to the sockets for IC27, 28 & 29.

Cheers.

Phill.

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Re: Atom mystery photos

Post by oss003 » Fri Oct 04, 2013 9:45 am

Hi jms2,

The first board could be this one:
Combikaart.png
It has following options:

- 32 kB RAM #0000-#7FFF
- 32 kB ROM #C000-#FFFF
- 8x 4 kB RAM #Axxx
- 8x 4 kB ROM #Axxx
- Write protect for RAM #Axxx/#1xxx (not on schematic)
- Battery backup for RAM

http://www.acornatom.nl/atom_nieuws/199 ... 913022.htm

The second board indeed looks like a replacement of the video RAM with buffers.

Greetings
Kees

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Re: Atom mystery photos

Post by jms2 » Fri Oct 04, 2013 11:33 am

Thanks Phill and Kees, both of your posts are massively helpful!! :D
Prime wrote:The second board that had fallen out looks to me like a video RAM replacement board, it has an 8K SRAM on it.

At a guess I would say it probably connects to the sockets for IC27, 28 & 29.
I will need to look closely at how the various groups of pins underneath the board might fit into those sockets. So far, I haven't been able to fit a position where every pin fits into a hole!

But, as an Atom newbie, I have two further questions:
1) If the large board, correctly identified by Kees, contains 32k RAM, is it still necessary to have a separate board with video ram on it? I assume so.
2) If I were to get one of your colour boards, am I correct in thinking that I could chuck out this handmade video ram board?
oss003 wrote:Hi jms2,
The first board could be this one:
- 32 kB RAM #0000-#7FFF
- 32 kB ROM #C000-#FFFF
- 8x 4 kB RAM #Axxx
- 8x 4 kB ROM #Axxx
- Write protect for RAM #Axxx/#1xxx (not on schematic)
- Battery backup for RAM
Yes - it is definitely that one, the text on the PCB matches. Thanks - I would have had to have read a lot of Atom Niews magazines to find that!

The board actually sounds pretty good from that specification. I'll get the article translated.

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Re: Atom mystery photos

Post by oss003 » Fri Oct 04, 2013 1:18 pm

Hi jms2,
jms2 wrote:At a guess I would say it probably connects to the sockets for IC27, 28 & 29.
The buffers are on the PCB so my guess is that the pins which are connected to the 74LS245 goes into the databuffer IC29 and the pins which are connected to the 2x 74LS244 goes into IC27 and IC28. The rest of the pins should fit into some other holes of the video RAM sockets. Watch if the power signals are ok.
jms2 wrote:But, as an Atom newbie, I have two further questions:
1) If the large board, correctly identified by Kees, contains 32k RAM, is it still necessary to have a separate board with video ram on it? I assume so.
2) If I were to get one of your colour boards, am I correct in thinking that I could chuck out this handmade video ram board?
The 32 kB RAM is located at #0000-#7FFF and the video RAM is located from #8000-#9FFF so that's a different area.

The colourboard can be installed instead of the handmade PCB.

You can quickly search in the index page, this board is called Combikaart:

http://www.acornatom.nl/atom_nieuws/index-an.html

Greetings
Kees

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Re: Atom mystery photos

Post by roland » Fri Oct 04, 2013 2:17 pm

The handmade board is indeed the video RAM, I remember it because I checked the Atom before shipping. The main reason that the video RAM is not on the combikaart is that both the 6502 and 6847 need access to it. That's why we never put video RAM on a ram/rom/memoryboard.

The combi-kaart provides 32k RAM from #0000-#7FFF, up to 16 banks at #Axxx (8 in eprom and 8 in RAM) and the complete operating system roms at #C000-#FFFF.

My own Atoms did also turn yellow during the years, but I have seen what Colin did to his Atom, I'll try this at home.

Enjoy your Atom. Just try to get it back working with minimum ram/rom (2K + 12K) and then start expanding with the combi-kaart or a more modern RAM/ROM board and colour board. I'm sure you'll get it running :)


Greetings,
Roland


BTW ... one of the designers of that combi-kaart is now 86 years old and is still attending every month's Atom User Group meeting. Speaking about average age :wink:
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Atom mystery photos

Post by CMcDougall » Fri Oct 04, 2013 10:46 pm

jms2 wrote:and also the mysterious switch on the back
I thought it was for turning the rom/ram board on/off, but Kees said it's a read/write ram switch :shock: wonder what 4k rom images wipe themselves :? only found about five that needed it on my beeb BITD.

Here is a different angle on mine, hopefully may give a little more light to your video board seating.
https://fbcdn-sphotos-h-a.akamaihd.net/ ... 1335_n.jpg

Hope you get it working John, it's a great feeling after all the cleaning! :D
Roland wrote:is now 86 years old and is still attending every month's Atom User Group meeting
:shock: =D> that will keep his brain very active, and live a longer life 8)
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Re: Atom mystery photos

Post by jms2 » Sat Oct 05, 2013 10:01 pm

CMcDougall wrote:
jms2 wrote:and also the mysterious switch on the back
I thought it was for turning the rom/ram board on/off, but Kees said it's a read/write ram switch :shock: wonder what 4k rom images wipe themselves :? only found about five that needed it on my beeb BITD.
Mine has two switches - one on the heatsink, and another one that is just floating about... When I've translated the dutch articles on the Combikaart hopefully I'll know what they both do!
CMcDougall wrote:Here is a different angle on mine, hopefully may give a little more light to your video board seating.
It might help a bit, but my board is completely different to yours so it'll have to serve as inspiration rather than something I can directly copy.

I'm itching to get the soapy water out and start cleaning the case! Also I'll look for an RTC board - if the two machines really did come from the same owner I half expect them to share a similar set of upgrades. So far my complete list for this one is:

5V power supply mod
Composite video port
Printer port
VIA
Bus buffers
32k RAM card
Joystick port
8k video ram

john

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Re: Atom mystery photos

Post by roland » Sat Oct 05, 2013 10:21 pm

Hi john,

I have another article / diagram about your combikaart at http://www.acornatom.nl/atom_nieuws/199 ... 911044.htm One of the switches (S2) is for write protecting the ram at #1xxxx and #Axxx. The other switch (S1) is for switching between two banks of rom at CDEF if you have a 27256 installed.

This switch is useless if a 27128 is fited on the board.

Regards,
Roland
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Atom mystery photos

Post by jms2 » Sat Oct 05, 2013 10:29 pm

roland wrote:One of the switches (S2) is for write protecting the ram at #1xxxx and #Axxx. The other switch (S1) is for switching between two banks of rom at CDEF if you have a 27256.
Pretty sure mine has a 27256, so that explains why there are two switches.

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Re: Atom mystery photos

Post by jms2 » Sun Oct 06, 2013 3:15 pm

I have cleaned the case and the keyboard now, and it all looks really good! :D
There is no RTC on this machine.

I think the next step is to replace all the electrolytic capacitors - I've measured a resistance of only 500 ohms between 5V and 0V, which doesn't seem right. Also some of the ceramic disc capacitors are chipped, so I might replace those as well.
roland wrote:One of the switches (S2) is for write protecting the ram at #1xxxx and #Axxx.
Thanks Roland, but what do you mean "ram at #1xxxx"?

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Re: Atom mystery photos

Post by CMcDougall » Sun Oct 06, 2013 3:51 pm

jms2 wrote:I have cleaned the case and the keyboard now, and it all looks really good! :D
There is no RTC on this machine.
some of the ceramic disc capacitors are chipped, so I might replace those as well
need photographic evidence! :) To be fair, my photos don't show a true likeness, even outside /without flash.
no RTC, what's the time?! time to get a AtoMMC to plug in there! 8) (mine ordered!)
one or two of my disc caps (light brown) are also chipped, but she works fine.
found this page :
http://wouter.bbcmicro.net/_archive/ato ... index.html
and mine does do a little of pic 1a, but not 1b, so I may fix that. Also explain's why my .WAV to tape don't show 100%, as only seen LOADER on when I tried to load Hyper Viper, but could be fine when I actually use my beeb/elk tape lead that's in another house :x
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Re: Atom mystery photos

Post by oss003 » Sun Oct 06, 2013 5:35 pm

jms2 wrote:Thanks Roland, but what do you mean "ram at #1xxxx"?
Hi Colin,

in Holland there was a patch in the Floating point ROM to install automatic #A000 ROM-switching software (Branquart) at #1000. Because in your configuration there's RAM from #0000 -#7FFF, there was a write protect switch installed to prevent writing into the #1xxx area.

Greetings
Kees

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Re: Atom mystery photos

Post by Prime » Sun Oct 06, 2013 6:11 pm

oss003 wrote:
jms2 wrote:Thanks Roland, but what do you mean "ram at #1xxxx"?
Hi Colin,

in Holland there was a patch in the Floating point ROM to install automatic #A000 ROM-switching software (Branquart) at #1000. Because in your configuration there's RAM from #0000 -#7FFF, there was a write protect switch installed to prevent writing into the #1xxx area.
It think possibly what was confusing him was that Roland said ram at #1xxxx (1 too many x), so it looked like an address bigger than 64K :)

Cheers.

Phill.

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Re: Atom mystery photos

Post by roland » Sun Oct 06, 2013 6:17 pm

It think possibly what was confusing him was that Roland said ram at #1xxxx (1 too many x), so it looked like an address bigger than 64K
I can confirm that there's one x too many. I shouldn't be typing at 12:21am (after a day working in the garden and struggling with Windows 7 in the evening) - that causes errors :oops:
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Atom mystery photos

Post by jms2 » Sun Oct 06, 2013 6:24 pm

Prime wrote:It think possibly what was confusing him was that Roland said ram at #1xxxx (1 too many x), so it looked like an address bigger than 64K :)
That's exactly what was confusing me! :lol:

I did guess that it might be a typo, but I wasn't aware of the significance of #1xxx so I couldn't see why you might want to write protect that.

Wouter's Atom repair page has convinced me that I really do need to replace all the electrolytic caps, so that will be my next step.

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Re: Atom mystery photos

Post by 1024MAK » Sun Oct 06, 2013 8:52 pm

Changing 1980's vintage electrolytic capacitors is a no brainer :D

As soon as you see symptoms of one failing, I recommend considering replacing all of them.

Mark

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Re: Atom mystery photos

Post by jms2 » Sun Oct 06, 2013 9:03 pm

CMcDougall wrote:
jms2 wrote:I have cleaned the case and the keyboard now, and it all looks really good!
need photographic evidence!
Here's what the exterior looks like now...
Note that I employ the Beebmaster-approved computer storage system, ie stacking them on top of something else! The RiscPC has the curious effect of making the Atom look pretty big.
P1030705.JPG

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Re: Atom mystery photos

Post by CMcDougall » Sun Oct 06, 2013 11:42 pm

^going by that pic John, the bottom half is more 'yellowing', and on top flat bit left & right like mine.

Glad you never took a pic of it like the boards at the start of thread :shock: , you must of took them in your plant growing tent! :lol:
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Re: Atom mystery photos

Post by jms2 » Mon Oct 07, 2013 8:15 am

:lol: Those were taken using macro mode, in terrible light conditions, with no flash! Makes it look like the 1970s.

The yellowing of the Atom case seems different to that of a BBC. It is certainly more patchy, and theres possibly a kind of coating layer which has worn off in places. I am keen on Retrobright, but I wouldn't dare use it on an Atom - unless someone out there has tried.

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Re: Atom mystery photos

Post by roland » Mon Oct 07, 2013 7:25 pm

I would leave it this way. After all, it's a 30 year old computer. And it looks better than mine at the moment.

Greetz,
Roland
FPGAtom: 512 KB RAM, Real Time Clock and 64 colours
MAN WOMAN :shock:

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Re: Atom mystery photos

Post by jms2 » Tue Oct 08, 2013 10:09 pm

I have managed to fit the video board. I can see why it fell out - the base is hard up against the 6847, so its pins are only just fitted into the sockets. Any heavy vertical shock load will cause it to drop out.

My plan is to renew all the caps and then try to boot the machine in its current configuration. Returning it to standard would obviously be sensible, but it would be a lot of work to do it, and then putting the mods back in again would be even more work. So I want to see if it will boot as-is first.

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