Click here for a list of the parts required to build an SC133, v1.0, modular backplane.

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

Introduction

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 SC133, modular backplane should look like.

Resistor 470R

Resistors can be fitted either way around, as they are not polarity dependent.

Resistors 4k7

Diode 1N4001

Diodes must be fitted the correct way around. The light coloured band at one end of the diode must be fitted into the circuit board at the end indicated by the silkscreen.

Capacitors 100 nF (0.1 µF)

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

The exact value of this component is not critical. The use of very cheap capacitors within the range of about 30 to 200 nF is acceptable.

Capacitor 100 µF

The silkscreen has a plus sign for the positive terminal and a hashed area for the negative terminal

Toggle switch

Light Emitting Diode (LED)

Reset switches

Fit and solder the two reset switches.

Voltage regulator 7805

Bend the legs such that the hole in the heat sink part of the regulator lines up with the hole in the printed circuit board. Bolt the regulator in place with an M3.5 nut and bolt, then solder the pins.

Headers (straight, single row)

These header pins may need to be cut from longer strips using wire cutters to cut the plastic.

Bus socket (horizontal)

Power connectors

Bus sockets (vertical)

Quick Tests

Repeat the check made earlier for a short on the power supply tracks. Connect the meter probes to the terminals of J2. This should be an open circuit, not a short. If you are using a digital meter set to measure resistance it will likely take a few seconds for the reading to stabilise as there are now capacitors on the power lines. A reading of more than 100k Ω (100000 ohms) is acceptable. Repeat with the toggle switch, SW1, in the other position.

Optional

The backplane includes a set of isolation points between the module sockets, as shown below. These allow some signals to be isolated between modules.

The PCB is manufactured with thin tracks linking these isolation points such that these signals are connected to all the module sockets. If you wish to isolate some signals it is necessary to cut the appropriate thin track on the solder side of the PCB.

The table below shows the signals that can be isolated.

Label	Signal name
TX	Serial transmit
RX	Serial receive
U1	User #1
U2	User #2
U3	User #3
U4	User #4

Should you wish to reconnect the signals you can solder a link in the appropriate place. Alternatively, you can solder header pins and use jumper shunts to connect the required signals.

Inspection

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.

Getting Started

The SC133 User Guide can be found here.

Other information about SC133 can be found here.