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Transformer Lead Color Code

A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors — the transformer's coils or "windings". Except for air-core transformers, the conductors are commonly wound around a single iron-rich core, or around separate but magnetically-coupled cores. A varying current in the first or "primary" winding creates a varying magnetic field in the core (or cores) of the transformer. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the "secondary" winding. This effect is called mutual induction. - Wikipedia

The following table represents the most common color coding for transformer leads.

Power Transformers
Primary LeadsBlack
If it is tapped: 
                   CommonBlack
           TapBlack / Yellow
            EndBlack / Red
High Voltage WindingRed
(center tap)Red / Yellow
Rectifier Filament WindingYellow
(center tap)Yellow / Blue
Filament Winding #1Green
(center tap)Green / Yellow
Filament Winding #2Brown
(center tap)Brown / Yellow
Filament Winding #3Slate
(center tap)Slate / Yellow
IF Transformers
Plate LeadBlue
B+ LeadRed
Grid (or diode) LeadGreen
A-V-C (or ground) LeadBlack
Tuning Slug Color Codes
455 kHz    1st IFYellow
 455 kHz    2nd IFWhite
455 kHz    3rd IFBlack
     455 kHz    OscillatorRed
10 MHz    1st IFGreen
10 MHz    2nd IF
10 MHz    3rd IF		Orange, Brown, or Black
Audio Transformers
Plate Lead, PrimaryBlue
B+ Lead, Primary
(w/or w/o center-tap)		Red
Plate Lead
(center-tapped primary)		Brown (or Blue*)
Grid Lead, SecondaryGreen
Grid Lead
(center-tapped secondary)		Yellow (or Green*)
Grid Return, SecondaryBlack

* Push-pull only

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