Getting an Atom up and running...

discussion of games, software, hardware & emulators relating to the Acorn Atom and Acorn System machines.
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danielj
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Getting an Atom up and running...

Post by danielj » Sun Oct 11, 2009 4:01 pm

I've found one in a box in the loft, I can't remember where I got it from but it's missing the processor. A couple of questions really:
What do I need by way of power supply?
Where can I get an appropriate 6502? Will a 65SC12 work too?

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IanS
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Re: Getting an Atom up and running...

Post by IanS » Sun Oct 11, 2009 4:07 pm

Depends if it's still got the voltage regulator wired in. If it has then an unregulated 8V was what Acorn supplied.

If you follow the instructions on page 13 of the TRM http://www.xs4all.nl/~fjkraan/comp/atom/atm/atm.html to bypass the regulators you should us a 5V regulated supply.

Not sure on the 6502 replacement.

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danielj
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Re: Getting an Atom up and running...

Post by danielj » Sun Oct 11, 2009 4:10 pm

Thanks for the link, exactly what I needed... It seems to have the voltage regulators installed. 8V seems a bit of an odd number...

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IanS
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Re: Getting an Atom up and running...

Post by IanS » Sun Oct 11, 2009 4:22 pm

danielj wrote:It seems to have the voltage regulators installed
Be careful. Mine still has the regulators installed but they are bypassed by fitting the links. You need to check if the Links on the board are made.

5V will always be safe, but may not work if the regulators haven't been bypassed.

Ian.

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Re: Getting an Atom up and running...

Post by danielj » Thu Oct 22, 2009 1:54 pm

Hello!
So, thanks Ian - it was running on 5V and I have got it up and running...

However, within about 10 minutes the keyboard stopped working :( - break key still seems to reset it but it doesn't respond to any other key presses.

So, I'm not sure the best place to start... Replacing the electrolytic caps? I have a scope, but I'm *really* not sure where I'd start with that.

Best,
Daniel
atomworking.jpg
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IanS
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Re: Getting an Atom up and running...

Post by IanS » Fri Oct 23, 2009 6:46 pm

Not sure what to suggest. As it basically works, I'd try re-seating all the chips, I dont think I've seen an atom that didn't have all the chips in sockets (did they ever make any?).

I know mine that was stored for a few years became much more reliable after re-seating all the chips.

Ian.

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Re: Getting an Atom up and running...

Post by Prime » Sat Oct 24, 2009 12:02 pm

danielj wrote:Hello!
So, thanks Ian - it was running on 5V and I have got it up and running...

However, within about 10 minutes the keyboard stopped working :( - break key still seems to reset it but it doesn't respond to any other key presses.
As IanS said, re-seating the chips is probably your first course of action, you might want to carefully clean the legs of any that appear dirty, Maplin do a polishing block suitable for this :

http://www.maplin.co.uk/module.aspx?moduleno=2109

The ICs that are involved in the keyboard scanning are IC25 the 8255 and IC26 the 7445. As reset is working and the machine is starting in text mode, I guess the 8255 is probably OK.

Whilst building the cone, I did have flakey keyboard behavior at one point which turned out to be the 7445. It is worth noting that the 74145 is also a compatible replacement.

Cheers.

Phill.

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danielj
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Re: Getting an Atom up and running...

Post by danielj » Sat Oct 24, 2009 4:40 pm

Good to know that if it's an IC it's got a replacement. I also noticed that C27 appears to have one broken lead - don't know exactly what the repercussions of that are.. Anyway, I'll pop to Maplin tomorrow and get the polishing block and a couple of those whilst I'm at it. Many thanks for the help!

Best,
Daniel.

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Re: Getting an Atom up and running...

Post by danielj » Sun Mar 27, 2011 11:17 am

Hello,

Resurrecting this thread after quite some time - arrival of child and a major bathroom renovation rather put paid to any time I had to spend tinkering with old hardware. I spent the last few days cleaning up all the ICs in my atom, slightly melting the corner of the 4 key with the soldering iron :( and replacing all the old electrolytics and the poorly soldered and twisted transistors etc. Anyway, it now functions properly and the keyboard is behaving itself (For reference, I did end up replacing the 7445).

I'd like to add the floating point rom, I have a couple of images I've dug off the net and burnt onto 27C32s but neither seem to work. I wondered if anyone would have a known-to-be-proper copy? And what would be the ROM of choice for IC24?

Very strange to think that this computer is a good 30 years older than my offspring and still behaving itself for the most part. Same can't be said for the once-working zx81 I've been trying to beat into shape.

d.

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Re: Getting an Atom up and running...

Post by Prime » Sun Mar 27, 2011 11:54 am

danielj wrote:Hello,
I'd like to add the floating point rom, I have a couple of images I've dug off the net and burnt onto 27C32s but neither seem to work. I wondered if anyone would have a known-to-be-proper copy? And what would be the ROM of choice for IC24?
You need either a 2532, or to make up a little patch board to adapt a 2732, IIRC it's just the swap of a couple of pins.
Very strange to think that this computer is a good 30 years older than my offspring and still behaving itself for the most part. Same can't be said for the once-working zx81 I've been trying to beat into shape.
Depending on what the fault is it may alas be the ULA that is dead, I had a couple of boards that where like that.

Cheers.

Phill.

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danielj
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Re: Getting an Atom up and running...

Post by danielj » Tue Mar 29, 2011 9:21 am

Prime wrote:
You need either a 2532, or to make up a little patch board to adapt a 2732, IIRC it's just the swap of a couple of pins.
Brilliant, thank you, I hadn't noticed that.
Prime wrote:
Very strange to think that this computer is a good 30 years older than my offspring and still behaving itself for the most part. Same can't be said for the once-working zx81 I've been trying to beat into shape.
Depending on what the fault is it may alas be the ULA that is dead, I had a couple of boards that where like that.
Unfortunately I think this is the case, I can see the K cursor briefly and as everything warms up it disintegrates into fuzz.

Thanks for your help,

Daniel.

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sirmorris
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Re: Getting an Atom up and running...

Post by sirmorris » Tue Mar 29, 2011 9:37 am

Hi Daniel,

I can supply you with an FP ROM and possibly a replacement 4 key - though this depends what issue Atom you have. Issues 4 and less have different keys to the individually switched Iss. 5s.

C

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Re: Getting an Atom up and running...

Post by Prime » Tue Mar 29, 2011 11:20 am

sirmorris wrote:Hi Daniel,
I can supply you with an FP ROM and possibly a replacement 4 key - though this depends what issue Atom you have. Issues 4 and less have different keys to the individually switched Iss. 5s.
Indeed Issue 5 board use the same keyswitches as the Beeb A/B/B+, so those can be used to replace them.

Cheers.

Phill.

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danielj
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Re: Getting an Atom up and running...

Post by danielj » Tue Mar 29, 2011 12:10 pm

sirmorris wrote:I can supply you with an FP ROM and possibly a replacement 4 key - though this depends what issue Atom you have. Issues 4 and less have different keys to the individually switched Iss. 5s.
Ooh, many thanks. So it's just the keytop, the switch itself is fine. I believe it's an Issue 5 (I've stared at it long enough, but the question's suddenly made me doubt my memory!). I've just got the bits and bobs to patch the 2732 to the 2532 socket, so I think I should be OK on the FP Rom - I may come crying for an image if neither of the ones I have work though. PM with what you'd like for the keytop :) In future I shall be removing the tops near the soldering iron.

Best,

Daniel

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Re: Getting an Atom up and running...

Post by sirmorris » Tue Mar 29, 2011 12:55 pm

Sorry to bear bad news but I only have an Iss.4 keycap :(

I'll keep an eye open for you though.

If you need a PROM blowing though just let me know.


C

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Re: Getting an Atom up and running...

Post by danielj » Fri Apr 01, 2011 9:05 am

sirmorris wrote:Sorry to bear bad news but I only have an Iss.4 keycap :(

I'll keep an eye open for you though.

If you need a PROM blowing though just let me know.


C
Ne'er mind, thank you anyway. It's slightly melted on a corner, one of those "Doh." cag-handed moments. I've managed to get the FP rom working on a little patch board now, and the composite video out seems to be behaving itself properly, the RAM is toasty warm and the whole thing seems to be behaving itself rather nicely... Is it yourself who produced the AtomMMC? Do you have any available still?

Best,
Daniel.

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Re: Getting an Atom up and running...

Post by sirmorris » Fri Apr 01, 2011 9:27 am

Nice, sounds like you're on your way!

On my Issue 3 machine I've tapped the composite video and fed it into the modulator where I've desoldered the RF connection, secured it, and replaced it with the composite feed. Now I get CVBS from the modulator socket and everything's really neat. The mod is very light and can be undone - though the rest of the Atom is thoroughly modernised so a lead into the modulator isn't going to make such a difference ;)

I've made a second order for AtoMMC2 boards and there'll be a run happening soon. I've just made the leap and introduced subdirectory support. It's not fully bedded in right now but should be by the time the next boards are made.

C

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Re: Getting an Atom up and running...

Post by danielj » Fri Apr 01, 2011 9:56 am

sirmorris wrote:Nice, sounds like you're on your way!

On my Issue 3 machine I've tapped the composite video and fed it into the modulator where I've desoldered the RF connection, secured it, and replaced it with the composite feed. Now I get CVBS from the modulator socket and everything's really neat. The mod is very light and can be undone - though the rest of the Atom is thoroughly modernised so a lead into the modulator isn't going to make such a difference ;)
A few years ago I was encouraged (through purchasing a SCART lead on eBay) to snip out a load of components in my ZX81 modulator in order to create the same situation. Complete hatchet job, thoroughly regret it.
I've made a second order for AtoMMC2 boards and there'll be a run happening soon. I've just made the leap and introduced subdirectory support. It's not fully bedded in right now but should be by the time the next boards are made.

C
Sounds brilliant. I shall affix some pins to PL8 in eager anticipation. Whilst I'm firing off questions, you wouldn't happen to know who'd do a DC socket that properly fits the PCB? The one that I've got there currently is a bit of a bodge and all the ones I find have symmetrical leads.

Best,
Daniel.

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Re: Getting an Atom up and running...

Post by sirmorris » Fri Apr 01, 2011 10:09 am

**EDIT** GAH! I just noticed you said socket for the board not plug for the lead..

That'll be a no, sorry.

My atom has a socket on a flying lead. Not ideal.

But if you wanted a plug for the lead:

Maplin do one but it's short. It still works but I wouldn't recommend them as a permanent solution. Order code is L49AY - (dc plug, 5mm external dia/2.5 internal)

If you can find one of these with an 11 or 14mm shaft it would be perfect. There's a guy on eBay does them.

http://goo.gl/BiFV1

C

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