• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

(newb) Why no white (-) leads on power trafo


2008-03-31 12:08 pm
OK - "live" and "neutral". Same question though: since the trafo primary will get "live" on one lead and "neutral" on the other, and the secondary pairs will output "live" and "neutral", why not indicate the distinctions?

As a novice, the lack of distinction is confusing and I thought maybe there was a concept I was misunderstanding.

But perhaps it's just a legal issue - i.e. by requiring users to confirm "live" and "neutral" with their own test equipment, the manufacturer avoids liability if, say, your trafo leads were labeled backwards, causing you to wire your circuit backwards, leading to damage or injury.
I think you're missing the point. The colour white indicates neutral. White and neutral both have very specific guidance to their use in the NEC and CEC. White wires must only be used when there is an uninterrupted connection from that wire to neutral(and thus to ground at the breaker box). However, the transformer primaries can easily be wired in a manner that that does not have an uninterrupted connection to neutral, such as use of a 2 pole power switch. If using such a switch to switch both AC leads, the colour black would be correct for both wires leading to the transformer.