Acorn Atom power connections on motherboard.

discussion of games, software, hardware & emulators relating to the Acorn Atom and Acorn System machines.
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apt-e
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Acorn Atom power connections on motherboard.

Post by apt-e » Wed May 15, 2019 8:01 am

Hi All,
This is going to sound a really stupid question, but bear with me...
I have just obtained an Atom, but the power lead is just a couple of wires soldered onto the pad where the power connector used to be. The power input seems to have been re-wired, as the voltage regulators have been removed, so I assume it needs a good 5volt 2-3amp psu.

The pads on the board are the original ones where the power socket was soldered on. Basically three in a triangle.

Problem is, I have no idea which is plus and which is negative on the pads, my board is 202,000 issue 5.

Can anyone please point out which ones are which, I don't want to take pot luck.

Any help, would be a great help from all you Atomizers!

Regards

Paul
Last edited by apt-e on Wed May 15, 2019 11:56 am, edited 2 times in total.

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Re: Acorn Atom power connections on motherboard.

Post by -B- » Wed May 15, 2019 3:02 pm

Do you have a multimeter?
Check for continuity between the large exposed area where the regulators used to be (this is GND) and the wires.
The pad furthest from the edge of the board should be +ve
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Re: Acorn Atom power connections on motherboard.

Post by 1024MAK » Wed May 15, 2019 4:33 pm

F3D8F94A-C517-4611-9F5C-9787E0948755.jpeg
Area of former regulators on an Atom board
Note that I did not notice that autocorrect had corrected “Vout” to “Volt”! [-X

BDB78E4F-04FE-46DF-94A9-6432A0474655.jpeg
Power socket on an Atom board
Where the voltage regulators have been removed, the +Vin and the +Vout/+5V connections are electrically connected via links on the circuit board (PCB).

The 0V/GND connection is under the power socket.

There are some hi-res photos of unpopulated Atom boards here :wink:

Mark
Last edited by 1024MAK on Wed May 15, 2019 4:49 pm, edited 3 times in total.

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Re: Acorn Atom power connections on motherboard.

Post by roland » Wed May 15, 2019 7:26 pm

Hi Paul,

Welcome to this forum. Enjoy your visits here. Please introduce yourself :)
If you're interested I have an original power connector for the Atom. Just P&P.

Greetings from the South of the Netherlands,
Roland
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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Thu May 16, 2019 9:38 am

Hi All,
Thanks for the information, now to see if the old girl works, I will keep you posted.

Hi Roland, if the old girl works, I would be very interested in the power socket you have , and will PM you.

Thanks again everyone.

Regards

Paul

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Re: Acorn Atom power connections on motherboard.

Post by trixster » Thu May 16, 2019 10:14 am

Hi Paul,

I have an Atom and am local to you. If you need a system to refer to at all when you’re fettling your new arrival, feel free to drop me a line and you can take a look at mine.
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Re: Acorn Atom power connections on motherboard.

Post by roland » Thu May 16, 2019 10:33 am

apt-e wrote:
Thu May 16, 2019 9:38 am
Thanks for the information, now to see if the old girl works, I will keep you posted.
Hi Roland, if the old girl works, I would be very interested in the power socket you have , and will PM you.

If the main board is in good condition we will certainly get it to work. Guaranteed 8)
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Re: Acorn Atom power connections on motherboard.

Post by DutchAcorn » Thu May 16, 2019 12:14 pm

apt-e wrote:
Thu May 16, 2019 9:38 am
Hi Roland, if the old girl works, I would be very interested in the power socket you have , and will PM you. ...
It’s would probably be nice if a matching plug can be included, that may well be your next challenge.
Paul

Image

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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Thu May 16, 2019 12:57 pm

Hi all,
Yes, the board is in pretty good condition, there isn't really any marks on it, so hopefully it will fire up.

Trixster, that brilliant, thank you very much for the offer, will maybe get the psu wires sorted over the next week, and if no life, I would be very greatful for you offer. Thank you.

Ive been after an Atom for years, so hopefully all can be made to work. The only thing I do know, is its expanded ram wise and has the A&F Utilirom fitted (not really sure what that does!)

I wil post some pics of my old girl, just in case anyone is interested in seeing another Atom (hopefully) come back to life.

Acorn rocks

Paul

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Re: Acorn Atom power connections on motherboard.

Post by hoglet » Thu May 16, 2019 1:33 pm

apt-e wrote:
Thu May 16, 2019 12:57 pm
The only thing I do know, is its expanded ram wise and has the A&F Utilirom fitted (not really sure what that does!)
Here's the manual for A&F Utilikit:
AF_Utilikit.pdf
(207.26 KiB) Downloaded 12 times
Dave

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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Thu May 16, 2019 2:06 pm

Nice one Dave, Thanks very much for the PDF.

Regards

Paul

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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Tue May 21, 2019 10:56 am

Hi All,
Whats the preferred way of posting photos on this from links only.

Paul

Wanting to post a few photos of my Atom while I restore it.

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Re: Acorn Atom power connections on motherboard.

Post by -B- » Tue May 21, 2019 11:42 am

apt-e wrote:
Tue May 21, 2019 10:56 am
Whats the preferred way of posting photos on this from links only.
I usually upload the photo into attachments (see tab below text entry box) then click [insert inline].
I use my phone mostly to keep up with forum posts and that's where most of my photos are so it makes it easy.

Neil.
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Re: Acorn Atom power connections on motherboard.

Post by 1024MAK » Tue May 21, 2019 3:19 pm

apt-e wrote:
Tue May 21, 2019 10:56 am
Hi All,
Whats the preferred way of posting photos on this from links only.

Paul

Wanting to post a few photos of my Atom while I restore it.
Please see the guidance in this post ;-)

Mark

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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Wed May 22, 2019 8:15 am

Hi All,
Here are a few pictures of my new Atom, not actually had time to do the PSU wiring yet, just checking the motherboard for any faults before hand.

Case has been reto-brighted, didn't come up to bad for my first attempt.

Hopefully, these pictures will show, thanks for the help with posting.

Paul
20190517_071640.jpg
20190517_071621.jpg
Last edited by apt-e on Wed May 22, 2019 8:16 am, edited 1 time in total.

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Re: Acorn Atom power connections on motherboard.

Post by trixster » Wed May 22, 2019 8:18 am

Very tidy :)
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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Wed May 22, 2019 10:05 am

Just noticed two parts of the motherboard have green corrosion on, would the vinger trick and IPA solve this? Section 1 & 2.

Section 3, there is a small bridge lead over these two pads, is this correct, and does the other ex-regulator pads need the same?

Thanks for all the help so far everyone.

Paul
pic1.jpg
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Re: Acorn Atom power connections on motherboard.

Post by roland » Wed May 22, 2019 11:29 am

Hi Paul,

The normal way to by-pass the 5V regulators is closing LK6 and LK7. With the wire bridge over IC54 (left regulator) and LK6 being closed, this is fine.

I wonder why the previous owner mounted PL6 (32p AB connector) because there are no VIA and no bus buffers installed in the Atom. This connector fairly useless here. However, if you need the buffer IC's (IC2, IC3 and IC4) I have several spares.

I have seen this kind of corrosion. IMHO it's only the varnish and it doesn't harm your Atom. Atom's don't have batteries that leak.

If you didn't already, just connect a 5V supply and bring her to life :D
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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Wed May 22, 2019 12:54 pm

Brilliant, thanks Roland.

Ive cleaned the case, keyboard. Will give the motherboard a wiz over and then give her a go at powering up.
I have a 5volt 4amp (regulated) PSU to hand, so I think that should do the job.

I have waited for years to get my hands on an Atom, so really looking forward to seeing what it can do.

Cheers

Paul

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Re: Acorn Atom power connections on motherboard.

Post by roland » Wed May 22, 2019 3:25 pm

Well, with some more memory (32kb) and an AtoMMC you can play 100 new games and much more old, classic games 8)

I really don't know why other computers were invented; all you need is an Atom :mrgreen:
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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Wed May 22, 2019 8:01 pm

Hi All,
Sadly, not all went to plan...

First power on, got garble and picture rolling with white lines.
20190522_181517.jpg
After a bit of poking around, machine booted, but then random characters appeared on screen.
20190522_182914.jpg
Seems to get worse the longer you leave the Atom powered up, until the screen garbles all together and then goes off....

Any ideas please people.........

Paul

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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Wed May 22, 2019 8:05 pm

Is the power in actually correct please...…………..
20190522_210207[1].jpg
Is there supposed to be a bridge between IC54 and LK7 ?

Thanks

Paul
Last edited by apt-e on Thu May 23, 2019 6:06 am, edited 1 time in total.

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Re: Acorn Atom power connections on motherboard.

Post by 1024MAK » Wed May 22, 2019 9:16 pm

The polarity of the power supply is correct.

If you have a multimeter, it would be good to check the voltage (should be between 4.75V and 5.25V) and then switch to the AC mV range (200mV range, or if the meter does not have this range, select the 2V range or equivalent). Post your results here.

It is also worthwhile checking each chip that is in a socket. Check that all legs are in the socket and press firmly on the chip to ensure it is fully in the socket. Do this for each chip.

After power on, if it does not reset, press BREAK, and see if that helps.

Again, it may be worthwhile testing the power supply pins on the major (large) chips with a multimeter. Be careful that you don’t let a probe slip and short anything out.

Mark
Last edited by 1024MAK on Wed May 22, 2019 9:18 pm, edited 1 time in total.

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Re: Acorn Atom power connections on motherboard.

Post by roland » Wed May 22, 2019 9:42 pm

You can also remove all chips and check the pins for corrosion. Clean them carfully with fine sand paper and put it back. I'd start with the 2114's in the video section (near the uhf modulator).
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Re: Acorn Atom power connections on motherboard.

Post by hoglet » Thu May 23, 2019 5:51 am

I suspect that some of the video RAM (possibly just IC42/IC43) are faulty. IC42/43 are of a different type to the rest, and are marked with blue dots, so are probably part of the original kit-built Atom.

Can you post a photo of what does the screen look like after CLEAR 4?

One thing you could try it to removing all the video RAM, and then just replacing IC42/43 but with two taken from elsewhere in the video RAM section.

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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Thu May 23, 2019 7:55 am

Hi All,
Thank you very much for your input into my Atoms problems, I did indeed plan to start on the video chips, I have managed to source some 2114s from the internet, just in case.

I am still not sure that the wiring to by-pass the regulators is correct, see above post about the bridges needed.

I will give everything a try in the next few days and post my results.

Fingers crossed

Paul

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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Thu May 23, 2019 2:42 pm

Can somebody post a photo of your Atoms power in section, to by-pass the regulators, maybe both sides of the board in the same location if need be.

Thanks

Paul

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Re: Acorn Atom power connections on motherboard.

Post by -B- » Thu May 23, 2019 3:08 pm

I added jumpers to LK6 and LK7 instead of a wire bridge...

267762CC-207D-424B-8BC8-35E9B6A0DE66.jpeg
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Re: Acorn Atom power connections on motherboard.

Post by apt-e » Thu May 23, 2019 3:54 pm

Brilliant, thanks.
On my motherboard ic54 and lk7 are not bridge, so will have to get that sorted, and then test again before I start re-seating chips and removing video ram.

Thanks again

Will keep you all posted.

Paul

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Re: Acorn Atom power connections on motherboard.

Post by 1024MAK » Thu May 23, 2019 3:59 pm

apt-e wrote:
Thu May 23, 2019 2:42 pm
Can somebody post a photo of your Atoms power in section, to by-pass the regulators, maybe both sides of the board in the same location if need be.

Thanks

Paul
Let me explain...

The Atom originally was designed to use two LM340T-5 5V 1A voltage regulators (IC53 and IC54)(the exact part number depends on which semiconductor manufacturer part was used, the more modern type go by the 7805 part number). These require an input of greater than 7.5V DC. Each one can then supply a regulated 5V DC supply at up to about 1A. If you have a circuit that needs more current than 1A, there were numerous options. Acorn went with just using two voltage regulators instead of a single higher current type.

However, you are not supposed to link the outputs of two different voltage regulator chips. As they may not have the exact same output voltage and therefore they will not share the current equally. But by using two independent voltage regulators, half the circuitry is fed from one voltage regulator. The other half is fed from the other voltage regulator.

Each LM340T-5 (or 7805) 5V 1A voltage regulator has three legs, hence the PCB has three PCB pads/holes: input, 0V/GND/ground/common, and output (+5V). Acorn also provided provision on the PCB for two wire links.

One wire link position, when linked across, by-passes one of the voltage regulators (IC54) by connecting the input and output circuits together. This is link LK7

The other link (LK6) connects the outputs of the two voltage regulators together. When both links are fitted, an external regulated 5V 2A (or higher current rating) PSU can supply the Atom circuitry.

Now on your board, all that has happened, is instead of using link LK7, they have instead linked one of the voltage regulator (IC53) inputs to the output. It does exactly the same thing as fitting link LK7.

So you don’t have to fit LK7, as the wire linking across the position where IC53 would have been fitted is doing the same thing.

Is this now making sense?

Mark
Last edited by 1024MAK on Thu May 23, 2019 4:01 pm, edited 1 time in total.

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