General Construction Notes

Component Specifications

The BOM will provide, for each part, a description and a package. The package reflects the footprint used on the PCB and so also defines the optimum size/shape of the part for fitting to the board. Other package/size parts may be used but may require to be 'prepared' prior to installation. For example, a 0.3" pitched axial resistor may be easily used in place of the specified 0.4" axial part and will simply require the legs to be formed at the 0.4" spacing. A 0.1" radial capacitor can be used in place of a 0.2" radial capacitor but will require that the legs be formed before installation.

The description for a part, particularly resistors and capacitors will often indicate voltage rating and a wattage rating. Where given, these reflect the 'standard' parts supplied in our kits and does not necessarily stipulate the actual specification for the part.

For example, many electrolytics are specified as 35V devices but in most cases these can be rated as low as 16V (most of our designs use 12V rails so 16V is perfectly okay, for 15V supplies we would recommend a minimum of 25V). You could possibly also use larger voltage devices but inevitably they are physically bigger and so there may be issues with component spacing. As another example we specify 0.5W for resistors, but in most situations you can safely use 1/4W resistors and sometimes even 1/8W resistors will be okay.

Tantalum capacitors that are mounted directly across the power rails should always have a voltage rating that is 3x greater than the power rail voltage i.e. on 12V rails you should have, as a minimum, a 35V device.

Electrolytic capacitors should have a voltage rating that is greater than the power rail voltage i.e. on 12V rails you should have, as a minimum, a 16V device.

Using higher voltage rated devices will not have any impact on the operation of the circuit but willusually result in physically larger components which may cause issues with assembly.


For most wiring we recommend using 7/02mm (24AWG) wire with a maximum outside diameter of 1.2mm. When wiring power rails (busboards and power supplies for example) we recommend 16/0.2mm (20AWG) with a maximum outside diameter of 1.55mm.

Other wire gauges may be used if desired but builders should be aware that using a larger gauge for the general wiring my prevent wires being inserted through restrain-relief holes on some of our PCBs .

© Copyright 2000. All rights reserved.     Revised: December 9, 2023