“not to get off topic, but if i'm correct, the hot and
neutral do make a difference, i have been told that if it is wired one way and then rewired opposite it will greatly reduce the life of the lamp.” - techieman33
There are 152 types of lamp
base currently in use ranging from B22d to
Wire Lead. Given this, a steadfast rule that applies to all will be not be appropriate. There is some basic principles about lamp bases and lamps however.
First, this is
alternating current. In other words, the
power heads
in one direction, than reverses itself and goes in the other direction 50 or 60 times a second. In other words, with AC
power, the
power does not go in from one end and out another though it’s easiest for wiring principals to consider it as doing this - one end in, one end out. How ever you consider it, a
filament lamp working under AC
power 99.5% of the time won’t matter which side you attach the hot to because the
filament will resist the
current flow no matter which side of it gets the
power first for 1/60th of a second as opposed to the other side of it getting
power for the other 1/60th of a second next. 120v
AC current works just like 208v currrent and other types of
current except instead of having two hot wires feeding the
filament 1/3 out of
phase with each other, the 120v lamp only has one hot. Both types of
current still have the
current going back and fourth in feeding the lamp.
This is not the case with DC
power where the flow goes from the negative to the positive. In cases like this while any AC lamp will work under DC
power, there can be at times DC lamps specifically designed for a direction of
current flow in preventing any
filament notching that might happen on the
power in side as can happen given the single direction of
power. You will probably never see such a lamp used on
stage and for general purposes such a consideration is not to be worried about.
So why does it matter at times which
wire is hot and which is
neutral on a lamp? This goes into the nature of the lamp
base design. Your medium screw E-26 or E-27 household lamp has a 1.1/16" dia. (26mm) for American lamps, Screw thread and a contact plate at the
base of it. Same with a
Fresnel’s Medium
Prefocus Single Contact P-28s lamp
base which is also about 1.1/16" dia (27.4mm Dia.) In having a wide
skirt at the top used to lock the lamp into place. You will also find that center contact plate on this lamp. For the most part, the screw
base be it from E-5 Midget Screw to E-40 European
Mogul Screw and
pre-focus single contact
point based lamps from P-14.5s to P-40s are the primary consideration for having a specific hot and
neutral. There are other types but these most explain the rule. When you remove one of these lamps from it’s lamp
base, there is a chance that you will touch or come into contact with the screw thread. Were this
pre-focus fin or screw thread hot, you would probably get shocked. Having a rule that the
neutral goes to the shell than makes sense in protecting the user’s of the lamp from
shock.
Most other lamp bases other than these two types will not matter which side is hot and which side is
neutral. Stick that GX-16d Extended
Mogul End Post/EMEP lamp into a
base, and both pins are the same side. Stick that
Leko lamp with a Medium 2-Pin G9.5 into it’s
base, and both pin holes are also the same size. Given both pins are alike, than wiring one side with a specific hot or
neutral will not matter because there is no way to ensure the lamp will be inserted
in one of the two specific ways. This also covers such lamps as
RSC / R-7s / R75 type Recessed Single Contact Double Ended Lamps such as many people would be using in
cyc lights or even construction work lights, down to the
wire lead lamp bases used on your Christmas Tree.
This said, there is like with the position orientated
prefocus Fresnel lamp bases above,
bi-pin and other types of lamp
base which use a position orientation
system to help ensure the lamp goes in in a specific way so as to optimize the
filament’s
layout in the
fixture. Such lamp bases as say a GY 9.5 Skirted Medium
Prefocus 2 pin which is similar to your
Leko lamp in style has one pin 3.2mm and one 2.4mm in dia. instead of both pins 3.17mm. In this case, besides having the pins of different diameters to help position the lamp in the
fixture, you would tend to want the hot
wire going to the larger pin because this has the primary amperage on it.
Given the specific pins, such lamps might also be optimized for
current fed from a specific direction in there being a possibility to what you were told, but not many of them would need to be. What ever the case of some very specific lamps, all
PAR lamps have two pins of an equal size and it will not matter which is hot and which is
neutral because one end of the
filament is the same as the other end of it.
Hope it helps..
Brian Shipinski
(
Festoon terminals would also be the wrong answer also.)
i don't use stagepins at the places I run lights, so I'm not too familiar with them anyways. but you seemt to know what your problem is anyways 
