Acorn Atom not working

[John Ferguson]

After nearly 40 years I have returned to my first love which was the Acorn Atom which I built in 1980 from a kit and added the colour board.

I have always regretted leaving it behind when an Atari and other home computers and PC came available. I tried various emulators but they did not capture my attention and restore my experience in the same way.

So in recent years and getting older I started to look around on the internet and on Ebay to see if I could buy one and get it working with only a limited amount of electrical knowledge. I know how to use a digital multi-meter but have no knowledge about the use of scopes. I have the technical manual, user guide and the circuit diagram.

Then I bought one on Ebay but this did not have a power supply. All the keys appear to work but on powering up no signal is received on a TV or monitor. Pressing break does nothing.

I bypassed the existing regulators by putting in the links 6 and 7 and fitted a new socket on the PCB. Then I connected a 5v DC SMP power supply.

Having just discovered this forum I am wondering whether a member could give me some advice on what to do next. It would be much appreciated.

John

[DutchAcorn]

Welcome to Stardot, John! You have come to the right place for help

How far have you got in powering it up and connecting it to a TV/monitor?

If you type a few random character and then press return, does it beep?

*edit: now see that you do not get any output on a TV

Do you realise that the port on the Atom is UHF out and you need to tune into the right frequency on the TV? Newer TV's may have trouble finding the signal.

[hoglet]

Why not start by posting a couple of high resolution photos of the insides?

Here's a link to the schematic (the best quality scan I'm aware of):
https://acorn.huininga.nl/pub/docs/circ ... iagram.gif

As Paul said, if you are connecting a TV via the UHF modulator, then make sure your TV has an analog tuner. What model is the TV?

A good first step is to make sure you can measure 5V across the GND and VCC pins of the 6847.

You can also get a composite video signal out of the Atom on PL4 pins 9 and 10. Pin 9 is the video and Pin 10 is GND. This should work with the composite video input of most modern TVs.

(It's actually quite rare for an Atom to produce no composite video output, as really all that has to be working is the 6847 and a couple of transistors)

Dave

[hoglet]

Oh, and Welcome! (above post edited a bit)

[danielj]

Welcome John the good news is almost every atom can be fixed!

d.

[John Ferguson]

Thank you very much for the comments received.

Its really good belonging to this forum.

There is no bleep after typing say line 10 test and pressing return. Break already pressed before.

Monitor connection to pins 9 and 10 of PL4 already made.

TV is a modern Samsung one. In addition to the monitor connection via component on the TV I connected the TV aerial to the modulator and set the channel on the TV to 36.

I will check some voltages on the 6847 and the 6502.

I imagine that as there is no bleep something major is not happening hence no output.

I will post some images.

John

[CMcDougall]

welcome John

typing 10 junk, would be ok until RUN
try CNTL G ,this should Beep.

have fun getting it going!

[hoglet]

Even if the 6502 processor is removed (i.e. no code at all running) you should still get some video output like this:

What you see here is the 2114 Video RAM chips initialized to random values on power up.

I would start by checking there is power to the appropriate pins of the 6847.

Also, do post some photos!

Dave

[Multiwizard]

Hi John,

welcome to this great Forum...


Greetings from my little Dutch Acorn Attic, Wim...

[martinw]

Welcome John

Might be worth a read ...

viewtopic.php?f=44&t=13531

... I was in a similar position not so long ago.

Martin

[oss003]

Hello John,

welcome and enjoy the forum .....

Maybe this post can help you: viewtopic.php?f=44&t=6318&p=60505&hilit=minimal+configuration#p60505

Greetings
Kees

[John Ferguson]

Well after the advice about checking the voltages sure enough when I fitted a new PCB connector for the power supply I had failed to connect one of the 2 0v connections.

The Atom is now working satisfactorily using component video only. Nothing via the modulator but I do not need it.

Only thing outstanding is that the loudspeaker is hardly audible.

Can you tell me how to fix this? Do I need a new speaker.

Next is the cassette recorder for saving programmes again from Ebay.

I assume that the connections for the microphone and earphones provided on the cassette recorder plus a ground connection common to both will do the job. Is this okay?

The encouragement I have received really helped.

John

[martinw]

These are ace

http://www.stardot.org.uk/forums/viewto ... mc#p170971

Martin

[hoglet]

Can you tell me how to fix this? Do I need a new speaker.

It's possible that capacitor C5 needs replacing.

If you look at the speaker circuit on the schematic (linked in my post earlier) it's quite simple.

Dave

[John Ferguson]

Thanks Dave for your comment about the speaker.

Does anyone know where I can get a list of commands for the floating point Rom?

John

[hoglet]

Does anyone know where I can get a list of commands for the floating point Rom?

Atomic Theory and Practice, Chapter 22 (Extending the Atom):
viewtopic.php?p=62322#p62322

Code: Select all

Floating-Point Statements
COLOUR, FDIM, FIF, FINPUT, FPRINT, FPUT, FUNTIL, STR

Floating-Point Functions
ABS, ACS, ASN, ATN, COS, DEG, EXP, FGET, FLT, HTN, LOG, PI, RAD, SGN, SIN, SQR, TAN, VAL

Floating-Point Operators
!, %, ^


Dave

[John Ferguson]

Outstanding issues for me now that the Atom is working are:-

How can I print from the Atom?

I see that there is an add on AtoMMC for solid state storage. How can I obtain this please?

John

[oss003]

To start printing type P.$2 and to stop printing type P.$3 but IC's 1 and 50 must be installed.

You can find a lot of Atomic expansions here: http://www.stardot.org.uk/forums/viewto ... cts#p86259

Greetings
Kees

[John Ferguson]

I thought I would show an image of my Atom's circuit board.

[oss003]

Hi John,

You need IC's 1 and 50 to print.

Greetings
Kees

[DutchAcorn]

Hi John,

You need IC's 1 and 50 to print.

Greetings
Kees

And you would need a connector fitted on PL5 to plug the parallel printer cable into the Atom.

[John Ferguson]

Thank you for the advice about printing.

John

[Multiwizard]

Hi,

don't we also need a little wire from pin1 of PL4 to pin17 of the PL5 for the 8th bit?

Or something like this?


Greetings, Wim...

[oss003]

That's only of you want to send 8 bits to the printer instead of 7.

Greetings
Kees

[John Ferguson]

I believe the Atom printer routines only output 7 bits. Is this a problem?

John

[oss003]

It will work for ASCII but you have to write a special 7 bit graphic print routine to make a screendump.
This is much easier with 8 bits.

Greetings
Kees

[John Ferguson]

Thank you Kees.

I remember that when I owned the atom way back I did write such a routine.

Perhaps I will make it one of my projects.

John

[Multiwizard]

This is much easier with 8 bits.

Ahaaa... LOL


Greetings, Wim...

[John Ferguson]

I am wondering whether it is possible to get some games for my Atom.

Could someone comment please.

John

[Multiwizard]

I am wondering whether it is possible to get some games for my Atom.

Could someone comment please.

John

On cassette, floppy or SD files?


Greetings, Wim...