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Component Identification

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Electrolytic capacitors (cylindrical shape) are marked with a band and ‘-‘ to indicate the negative lead.


The band on the diode shows polarisation, this must match the marking on the board.

Integrated CircuitThe top picture is an IC holder placed into the PCB, below are ICs. The notch on the holder should line up with the notch on the PCB.
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There is a flat edge on the LED, this should line up with the flat on the PCB.


These can go in either way around.


The D shape of the transistor, needs to be lined up with the D on the PCB.


Capacitor Values

The larger electrolytic capacitors tend to have the value printed on the side of them. Other capacitors, which are often smaller, may not have enough space to print the value in full and can use a 3-digit code. The first 2 digits are the first part of the number and the third digit gives the number of zeros to give it’s value in pF. Therefore '101' is a 100pF capacitor and '104' is a 100,000pF capacitor. See understanding ceramic disc capacitor values for a more detailed explanation.

Resistor Values

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This resistor has yellow, purple, black, gold bands has a value of 47 with no extra zeros so is a 47ohm resistor. The gold band indicates that this is accurate to ± 1%. A red, red, red, gold resistor would be a 2200 ohm (1k = 1000 ohm, 1M = 1000 k). See how to calculate and understand resistor values for a more detailed explanation.
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thanks very much

Rob Haywood

Rob Haywood

Hi Galen, If you email we'll have a look for you. Rob



Trying to identify a 3 legged component that I don't believe I've ever seen before. Schematic not available but I have photo. Thanks, Galen

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