Resurrecting an Atom that has not been touched for years

discussion of games, software, hardware & emulators relating to the Acorn Atom
markjw
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Resurrecting an Atom that has not been touched for years

Postby markjw » Sun May 28, 2017 9:35 am

Been having a sort of of old stuff I have here and found I still have an Atom that I purchased used years ago - it hasn't been powered up since the late 80's and I don't want to risk just plugging it in and having a load of fireworks/smoke! (made that mistake with my Atari ST - needs at least a PSU rebuild)

The original PSU is labelled as 8 volts, 1.8 amps DC and putting a meter on it is giving an unloaded voltage of around 15 volts - not tested it with any load.

I've opened the Atom up and it is an Issue 4 board with all the RAM sockets populated with 2114 chips, but no IC24 Option ROM or IC1 6522 and around 4 other empty sockets (for TTL chips?) - board appears remarkable clean for its' age and from the overall condition I suspect the original owner never used it much. Only issues I could see were some minor imperfections on the case and one of the memory ic sockets not fitted snugly to the board (probably like that from when it was made)

Would like to see if working again and maybe see about getting some upgrades for it - any help, opinions or thoughts very much appreciated
Mark

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hoglet
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Re: Resurrecting an Atom that has not been touched for years

Postby hoglet » Sun May 28, 2017 9:50 am

I would do two things before switching on:

1. Check the power supply drops significantly under load (of say an amp). Use a 10R power resistor, or a old 12V bulb (15W ish).

2. Make sure the Atom has not been configured for a 5V power supply (by bypassing the regulators). See this nice post from Kees:
http://www.stardot.org.uk/forums/viewto ... 73#p160773

On many Atoms, you see a screen of garbage when first switched on and need to press break to get the Atom to start. This is quite normal.

If you don't get any video output, try pressing Ctrl-G, and see if the Atom emits a beep.

Dave

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oss003
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Re: Resurrecting an Atom that has not been touched for years

Postby oss003 » Sun May 28, 2017 10:09 am

Hi Mark,

Nice to hear that another Atom is resurrected.

If you have checked the power supply and your Atom isn't working, please check this post:
viewtopic.php?f=44&t=6318&p=60505&hilit=minimal+configuration#p60505

Greetings
Kees

markjw
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Re: Resurrecting an Atom that has not been touched for years

Postby markjw » Sun May 28, 2017 10:16 am

cheers Dave,

1. Will do the load test on PSU before anything else.
2. Machine was running on the 8v PSU when last used so no 5v mod done - however using a more modern 5v switched mode PSU does sound like a better long term solution for the machine - I have a spare Linksys PA100 adapter from an IP phone that is 5v 2a that should do the job if I can find the connectors to make up an adaptor

Kees - thanks for the link - will work though their checklist if I have issues

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oss003
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Re: Resurrecting an Atom that has not been touched for years

Postby oss003 » Sun May 28, 2017 10:43 am

You can also find more information about Atomic hard- and software here: http://www.stardot.org.uk/forums/viewto ... cts#p86259

Greetings
Kees

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1024MAK
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Re: Resurrecting an Atom that has not been touched for years

Postby 1024MAK » Sun May 28, 2017 5:26 pm

markjw wrote:2. Machine was running on the 8v PSU when last used so no 5v mod done - however using a more modern 5v switched mode PSU does sound like a better long term solution for the machine - I have a spare Linksys PA100 adapter from an IP phone that is 5v 2a that should do the job if I can find the connectors to make up an adaptor.

Two things: with any replacement PSU, triple check the polarity. Yes THREE times! Saves on Magic bang followed by magic smoke...
Second, ensure that your 5V PSU is actually a regulated type. Check the voltage with the output not connected (unloaded). Then check with a suitable load (6V cycle lamp of suitable wattage). At no point should the output drop below 4.75V or go above 5.25V. Although a quality design should have a tighter tolerance. If you have an oscilloscope (or access to one) you can also check the noise and ripple levels.

Did I mention about checking the polarity?

Okay three things :P The power plug on most Atoms does not appear to like modern 2.1mm/5.5mm power connectors.

Mark
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roland
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Re: Resurrecting an Atom that has not been touched for years

Postby roland » Sun May 28, 2017 8:55 pm

Also good to know: if you don't fry the main board the Atom can always be repaired. Most parts are still available (on Ebay or on *. ) Just check the polarity of the power supply :roll: . I often use a generic 5V 2A USB power supply with a custom made lead.
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