Bizzarre electrical problems...

[Anonymous]

I took some pics of the area that seems to be causing some problems, but I'll see how well I can describe what's going on in case it's enough to trigger some bells or bring to mind some fluke that I'm not aware of.

I have been working on and off (more off than on) for well over a year at building my layout, within the last month the rear activity started and with enough benchwork for my mainline, today I finally did some of my first running tests before fitting the final pieces and securing the last of the mainline track to the benchwork.

My layout is using all 0-27 Lionel track, mostly O-54 curves or O-42 where I am using a switch in the curve. I have two bridge sections, one is using newer bridges, the other is using some (3) older post-war steel truss bridges.

The section in question is where the steel truss bridges carry straight section track into an O-42 switch, which turns left.

A test run up to where the switch will be works fine without the switch connected to the main line, I can add the switch in and run over it just fine, I can also run over the straights in the bridge just fine without the switch connected to them.

When everything is connected, I have problems if there is electrical load on the bridge side of the switch and the power to the mainline is on the opposite side of the switch (I haven't tried connecting the power on the other side of the switch). It seems as though there is a short... If I lift the straight off of the bridge, there no longer is a short.

I can't figure out any logical reason for this... Is there something in my configuration that I shouldn't be doing?

I'll also note that I have my O-42 switches wired so they can be powered seperately from track power. I have swapped out this particular switch, and an ohmmeter does not show any shorts in any of the track sections, except when the straight section is on the bridge and connected to the switch.

[wrmcclellan]

Will_K,

Could be one of two things:

1. If you are using a separate transformer to power the switch (for constant voltage), did you phase this transformer with your transformer that supplies the track?

2. Where you wired the hot wire into the switch is actually a ground/common - thus when you attach the switch it puts the constant voltage "hot" line onto ground of the track. which is then shorting against the bridge (this leads one to ask what is the bridge connected to?). Use your ohmmeter to confirm that the "hot" connection to the switch is not actually the common.

Regards,
Roy

[Anonymous]

Actually, at this point my hot wire for the switch is not yet connected to anything. The bridge is not connected to anything either... Although now that you mention it, I think that I do have my transformer sitting on top of it (KW) for my test runs.

I'll check the hot wire for the switch, but I am pretty doubtful that's the problem since most of these switches used to be in use on my dad's layout and that's where I did the conversion, I'm pretty sure they're all set up right.

It could be something with the transformer, I'll give it a try with the transformer sitting on benchwork (wood) instead.

[Anonymous]

Yep, seems that was the problem. Once I took the KW off the bridge, the problem went away.

[wrmcclellan]

Will_K,

Thats good news.

You may want to check out your transformer. Setting it on the metal bridge should not have caused an electrical connection. I do not have a KW, but my ZWs, SW, and 1034 that I just quickly checked are completely isolated from the bottom metal plate.

Regards,
Roy

[Chris F]

Could it be the weight of the KW rather than its electrical connections? I've had problems with center-rail insulators on O-27 track, especially the long straights. Try placing a similar weight on the bridge ( couple of telephone books ought to do it!) and see if the problem recurs.

[Anonymous]

One thing you have to remember, KW's were a little different. There are 6 terminal connections, going left to right they are labelled C U C(?). The two C's (I'm guessing it's C, but half of the lettering is faded on mine) have a line going across them indicating 18V, and indeed there is a constant 18V across the 1st and 3rd terminals. Going from the 2nd (U) terminal to the 3rd gives you the controlled voltage, and that's what I have connected.

What I did, however, is connected the outer rail to the U terminal. On ZW transformers, that is the ground. I forgot the peculiarity of the KW in that U is not ground, the third terminal is electrically connected to the ground. When the power is turned up, there is a potential difference (voltage) from U to the base plate on the transformer.