SC119, v1.0, Assembly Guide

Click here for a list of the parts required to build an SC119, v1.0, Z180 Memory Module.

Experienced builders can just go ahead and populate the board. There shouldn’t be any surprises to catch you out.

This guide assumes you are familiar with assembling circuit boards, soldering, and cleaning. If not, it is recommended you read some of the guides on the internet before continuing.

First check you have all the required components, as listed in the parts list.

Before assembling it is worth visually inspecting the circuit board for anything that looks out of place, such as mechanical damage or apparent manufacturing defects.

If you have a multimeter that measures resistance or has a continuity test function, check there is not a short on the power supply tracks. Connect the probes to each terminal of one of the capacitors, such as C1. This should be an open circuit, not a short.

The picture below shows what a completed SC119 Z180 Memory Module should look like.


Fit and solder the 10k resistor R1 (shown in yellow below).

These can be fitted either way round, as they are not polarity dependent.

IC sockets

Fit and solder IC sockets for U1, U2, U3 and U4

Be sure to fit them with the notch matching the legend on the circuit board, so you do not end up fitting the IC the wrong way round too.

The sockets should be fitted in the positions shown below.


Fit and solder capacitors C1 to C4.

These can be fitted either way round, as they are not polarity dependent.

Bus Connector

Fit and solder bus connector P1.

You may need to cut the connector strip to length (if starting with a strip more than 39 pins long). Long nose wire cutters snip through the plastic quite easily.

Take care to ensure the pins are parallel to the circuit board so that the board will be vertical when plugged into a backplane.

Header Pins

Fit and solder the right-angled male header pins, P2.

Take care to ensure the pins are parallel to the circuit board.

Jumper Pins

Fit and solder the jumper pins for JP1 to JP2.

Each of these is a single, 1 row by 3 pin header.

Fit and solder the jumper pins for JP1 and JP2.

JP3 is a single, 1 row by 2 pin header.


Fit and solder electrolytic capacitor C5.

It is important to fit this capacitor the right way round. The negative terminal is indicated with a ‘minus’ sign, as illustrated to the right. The negative terminal also has a shorter lead.

The capacitor is fitted in the position illustrated below, with the negative terminal at the bottom (hashed area) and the positive at the top (marked with a ‘plus’ symbol.

At this component is quite tall, it might be worth bending the leads such that the capacitor lays flat against the board, in the position indicated below. This avoids the possibility of it touching the next board on the backplane.


Remove any solder ‘splats’ with a brush, such as an old toothbrush.

Visually inspect the soldering for dry joints and shorts.

Clean the flux off with suitable cleaning materials.

Visually inspect again.

Before fitting the ICs, plug the board into an RC2014 backplane with no other boards fitted. Power the backplane and perform the following check with a voltmeter:

  • Check the supply voltage on the memory module, between, say, U4 pin 8 and U4 pin 16. This should be 4.5 to 5.5 volts, preferably 4.75 to 5.25 volts.

If all is well, power down and remove the memory module.

Integrated Circuits

Insert the ICs into their sockets, taking care to insert them the correct way round, as illustrated below. Be careful not to bend any legs over.


Fit jumper shunts in the positions indicated below.

JP1 and JP1 shunts are positioned to write protect the Flash memory.

JP3 is fitted to select Flash chip 1 (U1). To select Flash chip 2 (U2), remove the jumper shunt.

The following assumes you are using the Z180 CPU module SC111 and have the Small Computer Monitor, configuration S5, installed in socket U1 of this memory module. Jumper shunt JP3 should be fitted to select Flash chip 1 (U1).

Fit this module to a suitable backplane, along with the Z180 CPU module. Connect an FTDI style 5 volt serial cable to the CPU module’s serial port A, with the other end connected to a computer running a terminal emulation program. The terminal should be configured for 115200 baud, 8 data, 1 stop, no parity. Flow control can be either Off, or hardware RTS/CTS.

Turn the power on to the system. The terminal should show something similar to the illustration below.

Homebrew 8-bit retro computing