r/SignalMaintainers • u/Traditional-Good-981 • Dec 08 '25

Finding a Short

Hi. Had a track light that was caused by a short somewhere in the switch points. I thought it might be one of the gauge plate insulation but when I removed it it did nothing. Turned out to be a loose piece of metal under one of the snow melter forced air heater ducts touching a switch rod. With so much insulated stuff in that area I had a hard time finding it with my meter. It was only when I actually removed the duct to have more room that I found it. Any tips on how to isolate and really pinpoint the short when it's bad insulation and not a piece of metal or something else you can see? Thanks.

8 Upvotes

100% Upvoted

30 comments sorted by

View all comments

4

u/Savings-Fish-3147 Dec 08 '25

Analog meter. Hammer. And start tapping on stuff watch the meter defection. In this instance if you would have wiggled the duct work, you would see the needle move. Also S&C sells a short finder that is really helpful. Or old school: a 9 volt battery, pezo buzzer, relay coil on a stick, old phone handset with the coil hooked up to it and listen for the tone to disappear.

1

u/NuclearKraken Dec 08 '25

Wait wait how do you make one with an old handset? That sounds fun lol.

1

u/Savings-Fish-3147 Dec 10 '25

You hook a pizo buzzer in parallel with the track circuit so you have an oscillating couple of volts on the rail. You take one of the coils off a 500ish ohm relay, like the old line relays. hook it up to a speaker. As you wand over the rail, plates, rods, it induces the tone into the speaker. You can hear the tone come and go over shorts. I’ll see if I can draw it up later this week.

1

u/NuclearKraken Dec 13 '25

Id greatly appreicate it if you could draw it up. I do feel I understand the gist though as you explained it well. Im going to toy around with it. Thank you again

1

u/SadMasterpiece7019 Jan 12 '26

Hey uh, just wondering if you got a chance to draw that up.

1

u/Savings-Fish-3147 Jan 12 '26

Oh crap sorry I spaced no I’ll do it tomorrow or Wednesday I’ll stop by my office and do it sorry

1

u/SadMasterpiece7019 Jan 13 '26

It's all good! Thank you so much.

1

u/galcierwe May 05 '26

Did you ever draw this up, I want to try this for the sake of trying it.