Memory test for Atom?

discussion of games, software, hardware & emulators relating to the Acorn Atom
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roland
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Re: Memory test for Atom?

Postby roland » Fri Jun 30, 2017 9:56 am

roland wrote:First of all, to measure voltage the red plug of the meter should go into the right socket with µA,mA,V,Ω. The black plug goes into the middle socket with COM.

You can now check the voltage of the IC's. In many cases the 0V is located at the lower left pin and +5V is at the top right pin. The image below probably makes clear what I mean. Pin 1 is often marked with a small dot next to it. Use the black probe for 0V and the red one for 5V. Like Mark said, the voltage on each 2114 should be between 4.75 and 5.25V. This goes for almost every chip in the Atom.

2114A.gif
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mattd
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Re: Memory test for Atom?

Postby mattd » Fri Jun 30, 2017 10:48 am

Thanks all - I've learnt a lot this week. I think the problem is that my atom is slightly under powered. All the V checks on all the chips apart from the 6502, etc are around 4.48 - 4.51v. Nothing closer to 5v

Am I on the right track here?

Matt

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roland
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Re: Memory test for Atom?

Postby roland » Fri Jun 30, 2017 11:06 am

Yes, you're on a right track. Although many things will work you can get unexpected and unpredictable results when the IC's don't have the input voltage they need.

What is the voltage of the power supply when the Atom is not connected? If that is about 5V or higher then your power supply might be too weak for your Atom. The power lead to the Atom should not be too thin otherwise you might have too much loss in the lead. Keep it as short as possible.

Problems might disappear with a modern ram/rom board because these component are less power consuming.
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Re: Memory test for Atom?

Postby roland » Fri Jun 30, 2017 11:07 am

roland wrote:Yes, you're on a right track. Although many things will work you can get unexpected and unpredictable results when the IC's don't have the input voltage they need.

What is the voltage of the power supply when the Atom is not connected? If that is about 5V or higher then your power supply might be too weak for your Atom. The power lead to the Atom should not be too thin otherwise you might have too much loss in the lead. Keep it as short as possible.

Problems might disappear with a modern ram/rom board because these components are less power consuming.
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Re: Memory test for Atom?

Postby hoglet » Fri Jun 30, 2017 11:10 am

mattd wrote:Thanks all - I've learnt a lot this week. I think the problem is that my atom is slightly under powered. All the V checks on all the chips apart from the 6502, etc are around 4.48 - 4.51v. Nothing closer to 5v

Am I on the right track here?

The recommended minimum would be 4.75v, so it's certainly worth sorting the power supply before proceeding.

How exactly is it being powered at the moment?

My Atom will run Galaxians reliably at 4.40v, but will hang at 4.30v. However, it's using a modern RAM/ROM board, which is probably more tolerant than the original 2114 memory.

Dave

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Re: Memory test for Atom?

Postby mattd » Fri Jun 30, 2017 11:50 am

Hi all,

With my new found skills with the multi meter, the voltage coming is only 4.63v on the board (wife is a bit impressed to see me mucking around with a device :D :D )

here's how it's powered ..

How do i test the true voltage of the creative source - I tried shoving the multimeter prongs on the outside and the center prong but it's hard to get a read..
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oss003
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Re: Memory test for Atom?

Postby oss003 » Fri Jun 30, 2017 11:58 am

Do you have an USB power supply?
If so then you can try that supply.

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Kees

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roland
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Re: Memory test for Atom?

Postby roland » Fri Jun 30, 2017 11:59 am

Your power supply is rated at 1.5A For a full expanded Atom this is often not enough. I used a 5V/2A power supply for my Atoms.
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Re: Memory test for Atom?

Postby oss003 » Fri Jun 30, 2017 12:19 pm

You can measure the amps now ....... ;)

According to the Technical Manual, the original 8V Acorn Atom supply was 1,6 A.

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Re: Memory test for Atom?

Postby 1024MAK » Fri Jun 30, 2017 8:16 pm

Hi Matt

I would say that the power supply unit (PSU) you are using is unable to supply the power that the Atom needs. Hence why the voltage from your PSU is dropping below 5V (PSU often have output power limiting circuitry to protect themselves).

As suggested by others above, try with a 5V 2A regulated power supply.

Important: always test the polarity of any PSU you try before connecting to the Atom. Then double check it. Then triple check it. If you get the polarity wrong, it could kill most of the chips on the Atom :(

On digital multimeters, with the red probe/lead in the V socket and the black probe/lead in the COM socket, with the red probe/lead connected to the positive (+) PSU output connection/terminal and the black probe/lead connected to the negative (-) PSU output connection/terminal, the meter will only show the DC voltage. If you reverse the probe/lead connections to the PSU output connection/terminals, the meter will again show the DC voltage, but this time with a negative (-) sign to the left of the voltage display.

It's easiest to compare with your existing PSU.

Measuring the output of PSU on the mini power connectors is a bit tricky. A third hand would come in useful :P
Stuff one probe in the centre hole of the PSU output connector, then while still putting gentle pressure on it, hold the other probe on the outer metal "barrel" of the connector.

Mark
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mattd
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Re: Memory test for Atom?

Postby mattd » Sat Jul 01, 2017 3:10 am

Hi Mark,

Good advice and thanks. Now the only problem is that my underpowered supply has just 'popped' - I don't know if it was myself trying to get the polarity? Anyhow I have a new %V 3A supply. First I was told 3A is OK as current is drawn right? Bigger question is how do work out the polarity the Atom wants?
Just to explain, my atom came with no PSU so I had a mate cobble something together. He's put a wire - with one wire (white side) attached to the original dc connector on the atom, with the other wire attached to the resistor C12 (-ve end). My intuition would suggest the polarity is +ve right?


Matt

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Re: Memory test for Atom?

Postby mattd » Sat Jul 01, 2017 5:44 am

OK - I think we close this one off!!!! :D :D :D
I've fixed it!
Even after sourcing a new PSU (5v 3a) and getting the polarity right (phew!) , the voltage was still too low. So thanks to Roland's post, I shortened the lead my mate had soldered to the power connector and bingo! 4.8v across the ram and Galaxian and astro bird work just fine!

Thanks for all of your help - especially Mark to convince me to get the multimeter. I've learnt about some code, voltages, polarity and the Atom in general!
You're all a great bunch of helpful people - thanks again :wink:
Matt

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Re: Memory test for Atom?

Postby 1024MAK » Sat Jul 01, 2017 9:15 am

Hey, well done Matt :D

Good to hear that it now working well for you =D> =D> =D>

Mark
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roland
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Re: Memory test for Atom?

Postby roland » Sat Jul 01, 2017 9:52 am

Congratulations and well done =D>

There is still much to learn (for example that C12 is not a resistor but a capacitor) but you've taken the first steps into the world of the Atom.

Begin with the basics and build up your knowledge. We're here to support you!

Have fun with your Atom!
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Re: Memory test for Atom?

Postby oss003 » Sat Jul 01, 2017 10:17 am

Well done Matt, welcome to the club of working Acorn Atoms ...... :D

Greetings
Kees

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Re: Memory test for Atom?

Postby Multiwizard » Sat Jul 01, 2017 12:15 pm

=D> well done indeed Matt =D>


Greetings, Wim... :-)


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