Building a System 1 Trainer

System 1 Trainer Front View Acorn


Although originally designed for the Centre for Computing History as an educational tool the System 1 Trainer is an ideal starter project and an excellent introduction to the world of real programming !

The original Acorn System 1 documentation is very good and provides useful guidance on the assembly process that is applicable to this project as well: Acorn System 1 Technical Manual.  I would suggest starting by reading that and then refer to my more specific information below.

Tools Required

Not many tools are required for this project - a decent electronic soldering iron, a pair of cutters & long nose pliers and some solder ! (I would recommend sticking with good old leaded solder rather than the lead free stuff as the solder flows much better for hand soldering.)

A voltmeter will be useful for e.g. checking the power supply.

Order of Build

Here is a suggested order in which to load the components:

EPROM Choices

You can fit either a 2716 or 2732 EPROM and this is selected by Links LK1 and 2.

The kit is provided with a 2732 EPROM so fit the links in the two holes to the left (nearest to the display).

Power Supply Choices

The board can be powered from either a 5V supply e.g. a USB power supply or an unregulated DC supply (7 to 9V).

To power the board from a 5V supply then just fit LK5.

To power the board from an unregulated supply fit IC13 together with the three capacitors C11,12 & 13.

Please check the power supply connection before switching on !, the centre pin of PL3 is the positive.

A USB power supply can be used as a power source with the supplied USB to power jack cable.

Switching On

Before switching on its worth spending the time to inspect the underside of the board for shorts or missing solder connections. Check the 6502 is fitted the right way around.

The board draws between 200 and 250mA depending on how many display digits are lit up.  If you have a bench power supply then you could initially power it from that and set the current limit appropriately, otherwise you'll just have to go for it !

When the board is powered up the processor is not reset and you'll typically just get one dot on the right hand display or garbage, press the RESET button and you should get 8 dots on the display, if you do all is looking good.  By pressing MODIFY and entering an address you can then press UP and DOWN to inspect memory.

Fault Finding

If you're unlucky enough to have problems then here are some basic checks you can do:

If you get really stuck then I can offer a repair service, please drop me an email.


System 1 Trainer Kit BOM

Here's what's included in the System 1 Trainer Kit:



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