Click here for a list of the parts required to build an SC141, 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 SC141, modular backplane should look like.
Bus socket (horizontal)
Fit and solder the right angled female header, 1 row x 40 pin, S13.
Bus plug (horizontal)
The bus header plug is a modified 2 row angled male header. The second row needs to be removed. A modified 2 row header is used instead of a single row header as the pin position matches the single row socket, as illustrated below, while the common single row header does not. Single and double row headers, and how to modify them, is explained here.
Fit and solder the modified right angled male header, 2 row x 40 pin, P1.
Capacitors 100 nF (0.1 µF)
Fit and solder capacitors C1 to C13.
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.
Bus sockets (vertical)
Repeat the check made earlier for a short on the power supply tracks. Connect the meter probes to either end of one of the capacitors. 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.
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.
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.
The SC141 User Guide can be found here.
Other information about SC141 can be found here.