I am about to start wiring a new tube amp and did a search for "standard" wire color (or colour for us down under) codes. When I was an apprentice there was a very strict "correct" wire colour to be used for each tube pin and heaven help anyone who used the wrong colour to connect a grid or a screen or cathode or whatever. Of-course that was back in the day when Apprentice Masters indicated your mistakes/faults with a smack in the head.
I found this:
http://www.tpub.com/content/draftsman/14040/css/14040_91.htm
For the possible benefit of others I posted the link. It does make set to work and fault finding easier.
Cheers,
Ian
I found this:
http://www.tpub.com/content/draftsman/14040/css/14040_91.htm
For the possible benefit of others I posted the link. It does make set to work and fault finding easier.
Cheers,
Ian
When I was a teen 
I joined the Royal Navy where I was taught the following::-
Red - HT Wiring (B+)
Orange - Screen grid
Green - Signal Grid
Brown - Heaters
Black - Earth or chassis.
Any other odd wiring like to cathodes was Pink.
White was reserved for very high voltage or EHT wiring.
Blue was reserved for negative voltage supplies.
Not too far from the list previously given but I don't think the colour rules were ever 'hard and fast' and there were slight variations.
Surprisingly, I have serviced many old valve amplifiers since and many conformed to the above standard, specifically the brown heater wiring.
I joined the Royal Navy where I was taught the following::-Red - HT Wiring (B+)
Orange - Screen grid
Green - Signal Grid
Brown - Heaters
Black - Earth or chassis.
Any other odd wiring like to cathodes was Pink.
White was reserved for very high voltage or EHT wiring.
Blue was reserved for negative voltage supplies.
Not too far from the list previously given but I don't think the colour rules were ever 'hard and fast' and there were slight variations.
Surprisingly, I have serviced many old valve amplifiers since and many conformed to the above standard, specifically the brown heater wiring.
I have got this info:
EIA RETMA Chassis Wiring Color Code
In the 1950's the Radio Electronics Television Manufacturers Association (RETMA), now part of the Electronics
Industries Alliance (EIA), used color codes to identify electronic parts, such as capacitors and resistors. In addition,
there is a lessor-known EIA equipment Wiring Code that identifies the type of circuit each wire serves.
Color - Circuit
Black - Grounds, grounded elements and returns
Brown - Heaters or filaments, off ground
Red - Power Supply B-plus
Orange - Screen grids
Yellow - Cathodes
Green - Control Grids
Blue - Plates
Violet - not used
Gray - AC power lines
White - Above or below ground returns, AVC, etc.
Most electronic manufactures of that era, including the popular Heathkit , used this color code for chassis wiring.
When working on antique electronic equipment of that era, this color code can identify circuit wire functions
without a schematic or wiring diagram.
Reference verification: Popular Electronics Magazine 1958 July, page 78
EIA RETMA Chassis Wiring Color Code
In the 1950's the Radio Electronics Television Manufacturers Association (RETMA), now part of the Electronics
Industries Alliance (EIA), used color codes to identify electronic parts, such as capacitors and resistors. In addition,
there is a lessor-known EIA equipment Wiring Code that identifies the type of circuit each wire serves.
Color - Circuit
Black - Grounds, grounded elements and returns
Brown - Heaters or filaments, off ground
Red - Power Supply B-plus
Orange - Screen grids
Yellow - Cathodes
Green - Control Grids
Blue - Plates
Violet - not used
Gray - AC power lines
White - Above or below ground returns, AVC, etc.
Most electronic manufactures of that era, including the popular Heathkit , used this color code for chassis wiring.
When working on antique electronic equipment of that era, this color code can identify circuit wire functions
without a schematic or wiring diagram.
Reference verification: Popular Electronics Magazine 1958 July, page 78
Green. The power cord is likely to not be near grid circuits (you don't want a whopping big 120VAC source of hum close to a grid circuit!), so there won't be much confusion. But often inside audio amps the grid circuits are comprised of resistor leads to ground, and capacitor leads to the previous stage's plate. Thus no hookup wire involved. As driver tubes are usually mounted near their output tubes.
Often in consumer electronics of the day, they used whatever color wire they could get cheap, so don't get puzzled when the wiring colors don't make sense.
Oh, and violet wire codes to negative power supplies, like a bias supply for the output tubes.
When I was being taught electronics they made us just use one colour of wire to make things as difficult as possible.
Wiring 25 way connectors to each other was great fun !
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