Lionel LW transformer shows voltage when off

Get rid of the digital meter and get one with a needle. It will give more accurate readings. Or put a light bulb across the posts and put your meter on that.  Tiny amounts of leakage or inductance will show up on digital meter. But there is no power there. It does not mean anything.

@David Johnston posted:

Get rid of the digital meter and get one with a needle. It will give more accurate readings. Or put a light bulb across the posts and put your meter on that.  Tiny amounts of leakage or inductance will show up on digital meter. But there is no power there. It does not mean anything.

This is the answer. It IS  your meter.

The Lionel transformer is a unique design and the LW,  like other multi-control transformers, when the throttle is 'Off' you still have about 5 volts on the track between posts A and U.  Pushing the whistle gives a surge of DC voltage to pull in the whistle relay, and then a holding voltage to keep it pulled in while the voltage coming from the throttle runs the whistle motor.  If you have the schematic available, you can determine what voltages to expect between each post.  Get Greenbergs Repair and Operating Manual for Lionel 1945-69.

Thx guys

FYI - found these pics of the LW manual. Says A to U is 8 to 18 volts, which was Lionel's design target. So as @CALNNC wrote, you should expect to see some voltage A to U when handle is at off position.

@CALNNC posted:

The Lionel transformer is a unique design and the LW,  like other multi-control transformers, when the throttle is 'Off' you still have about 5 volts on the track between posts A and U...

No, the LW is no different than any other postwar transformer. The wiper comes completely off of the secondary in the "off" position. Any voltage reading while "off" is due to the combination of a cheap meter and its reading of an unusable capacitance voltage. As soon as you put any load on it, there is zero volts.

@MED posted:

FYI - found these pics of the LW manual. Says A to U is 8 to 18 volts, which was Lionel's design target. So as @CALNNC wrote, you should expect to see some voltage A to U when handle is at off position.

No, the wiper comes completely off of the secondary in the "off" position. Any voltage reading while "off" is due to the combination of a cheap meter and its reading of an unusable capacitance voltage. As soon as you put any load on it, there is zero volts.

The LW is one transformer I do not own to confirm this, just reading the schematic and pictoral wiring, but from how it is drawn, if output goes to zero as you describe, the pilot lamp should go out too, and also increase in brilliance as you advance the throttle.  Does it? Or is there is something wrong with how Lionel drew the circuit?  Inquiring minds want to know.(The old National Enquirer promo)

WIth throttle at zero, the light bulb goes out.  And as you move the throttle up, the light intensity does increase.  Not to confuse the topic, but the meter itself is a Klein, so it's a decent meter. I'm sure you can find more expensive ones, but I know from experience that you can find a lot of cheaper ones (been there done that   )   Also, as I said, with throttle off and just plugged in, bulb is out, BUT I can hear a low hum from the transformer. So I believe that their is some voltage there. If that is considered 'normal', that is fine. I was just trying to figure out if it was proper or not.

The hum is normal. There is no on/ off switch for the transformer itself. When you plug it in, you get voltage to the primary coil. If the handle is in the off position, there should be no voltage from the variable output. As others have said, use an analog (needle) type meter. If you are reading a voltage with that, then the variable wiper is touching the secondary winding.

Chris P&O

@TJm posted:

...with throttle off and just plugged in, bulb is out, BUT I can hear a low hum from the transformer. So I believe that their is some voltage there.

You've just described all postwar transformers... the hum is always there when plugged in, some louder than others.  There is no technical term for "some voltage there", only that whenever the transformer is plugged in, the primary is energized, all fixed voltage binding posts are at their potential, and variables have no potential when "off". The wiper on the LW rests on a non-conductive, non-energized pad at the low end of the secondary windings. Contact with the first set of windings on the secondary should give a reading of 6-8 volts on A-U at 110-125 volts input at the mains.

Not an LW, but I have a rebuilt KW whose wiper doesn't quite come off the primary if you just turn it down to "zero". You have to push it hard to get it to turn off. This may well have been a consequence of the rebuilding--not original condition. Haven't tried to fix it.