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The Resistor Colour Code

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How to read old style resistors.
The body colour is the first digit.
The next digit is the Left hand end colour
The spot in the middle of the body is the multiplier.
The Right hand end colour is the tollerance ie Silver,Gold etc.

How to remember the colour code.

Something I picked up many years ago.

0=Black
1=Brown
(2) Red=Richard
(3) Orange=Of
(4) Yellow=York
(5) Green=Gave
(6) Blue=Battle
(7) Violet=In Vain
8=Grey
9=White

Richard Of York Gave Battle in Vain.

Remember that line and add Black = 0, Brown = 1, Grey = 8 or White = 9 (as above) to complete the sequence.

How to read Capacitor Codes
Large capacitors have the value printed plainly on them, such as 10uF but smaller disk types along with plastic film types often have just 2 or three numbers on them.
Most will have three numbers, but sometimes there are just two numbers. These are read as Pico-Farads. An example: 47 printed on a small disk can be assumed to be 47 Pico-Farads (47pf).
Now, what about the three numbers? It is somewhat similar to the the resistor code. The first two are the 1st and 2nd significant digits and the third is a multiplier code. Most of the time the last digit tells you how many zeros to write after the first two digits.

1 mili Farad is 1/1,000th or .001 times the unit. (10-3)
1 micro = 1/1,000,000 or 0.000 001 times the unit (10-6 )
1 nano = 1/1,000,000,000 or 0.000 000 001 times the unit (10-9 )
1 pico = 1/1,000,000,000,000 or 0.000 000 000 001 times the unit (10-12 )

Multiplier
Third digit Multiplier (Multiply the first two digits by this number gives you the value in Pico-Farads)
0 1
1 10
2 100
3 1,000
4 10,000
5 100,000
6 unused
7 unused
8 .01
9 .1

Now for an example: A capacitor marked 104 is 10 with 4 more zeros or 100,000pF which is referred to as a .1 uF capacitor.

Capacitor Colour Codes

In general the capacitor colour code follows that for resistors.
The following data is taken from cards issued with Practical Wireless in the eary 1970's.

Audio Reference Chart

The following pages are taken from a data sheet issued free with Practical Wireless in 1968.
The first sheet shows Stereo Cartridge Connections. And highlights the different pin and tag connections for cartridges used at that time.
Cartidges include: ACOS,BRS,DECCA,Empire,Pickering,Shure,Tannoy,Goldring etc.
The fourth sheet is of Tape Head and Track dimensions. And shows the layout of tracks and their dimensions.

This sheet shows Pick up arm and shell connections as well as the colour codes then in use.

Connections to DIN standard plug and sockets as well as Phono and Jack are listed here.

Loudspeaker Transformer Ratio Table

The following sheet is from Radio Constructor Magazine and covers both trainsistor and valve push pull output stages. Ratio values are given for the differing load impedences verses the speaker impedence.

With thanks to B Patten-Walsh who kindly supplied these sheets.

Last updated 5.12.2008

2003-2008 © Maurice Woodhead