SC133, v1.0, Assembly Guide

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.


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

Fit and solder the 470R resistor R1 (shown below in red).

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

Resistors 4k7

Fit and solder the 4k7 resistor R2.

Diode 1N4001

Fit and solder the 1N4001 diode D1.

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)

Fit and solder capacitors C1 to C11, and C102.

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

Fit and solder capacitors C101 and C103.

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

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

Toggle switch

Fit and solder the toggle switch SW1.

Light Emitting Diode (LED)

Fit and solder the LED (LED1).

It is important to fit the LED the correct way around. LEDs usually have a small flat side to indicate the cathode (the negative end). This should be positioned to match the flat side shown on the circuit board (illustrated to the right). Also, the cathode pin on the LED is usually shorter than the other pin (the Anode).

Reset switches

Fit and solder the two reset switches.

SW2 faces straight up.

SW3 faces forward.

Voltage regulator 7805

Fit and solder the 7805 voltage regulator U1.

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)

Fit and solder the pin headers P1, P2, and P3.

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

Bus socket (horizontal)

Fit and solder the right angled female header, 1 row x 40 pin, SK12.

Power connectors

Fit and solder the 2.1 mm power jack socket, J1.

Fit and solder the two screw terminal blocks, J2 and J3.

Ensure the the wire entry holes face the edge of the PCB.

Bus sockets (vertical)

Fit and solder the straight female headers, 1 row x 40 pin, SK1 to SK11.

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.


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.

LabelSignal name
TXSerial transmit
RXSerial receive
U1User #1
U2User #2
U3User #3
U4User #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.


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.

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