Testing for shorts...

[tetters]

So.

I've been filling some "holes" in my track work using some PCB ties that have an isolation gap in them. When I power up the layout, everything is fine, no shorts. Power Cab boots up, locos run, Torts are just peachy. When I do a test by dropping a piece of rail across the rails I get hard short...which is good. Its what you want to happen. I've heard it called the quarter test in couple of different places... anyways...

When I use a VOM on the rails with the DCC off (or even on for that matter) the VOM reads a dead short. Is there any particular reason for this? Is it because that even when powered off the sum of the parts, i.e. layout wiring, track work, decoders, electronic tidbits, DCC system create a circuit that allows the VOM to see (perhaps what it "thinks") is a dead short?

Does that make any sense? I've just never tested the track work installed and on the layout like this, only on the bench, and wonder if there is a logical explanation for it.

Otherwise, I'll keep plugging ahead and accept it as normal.

[nachoman]

disconnect (not just unplug or turn off) your power supply, then test

[Gary S]

Tetters:

Are there any locos sitting on the track duirng your VOM test? They'll most likely read as a short.

Other than that, you may be reading something in the DCC unit itself. Try disconnecting that from the rails/buss and see what you read. Also, is anything else connected to the track or buss? Electronic stuff?

Anyway, try to isolate any loads that are connected across the track.

[BR60103]

Second what Gary S said. Then, just for fun, unplug your DCC from the wall and read the resistance over its terminals.

[tetters]

disconnect (not just unplug or turn off) your power supply, then test

I was just unplugging it....I'll try disconnecting the power supply completely.

Tetters:

Are there any locos sitting on the track duirng your VOM test? They'll most likely read as a short.

Other than that, you may be reading something in the DCC unit itself. Try disconnecting that from the rails/buss and see what you read. Also, is anything else connected to the track or buss? Electronic stuff?

Anyway, try to isolate any loads that are connected across the track.

There are a couple things that did not occur to me last night that I could have checked. Yes, I have two locos sitting on the track right now, and they were there last night when I used my VOM to test for isolation. It also never occured to me that I should disconnect the Power Cab and then test for continuity. I have a nice collection of electronic tidbits (decoders for the Torts, Hex Frog Juicer board...) wired to the track buss too, however it did actually occur to me that these little gems even when powered off could allow a meter to sense continuity in the rails.

Second what Gary S said. Then, just for fun, unplug your DCC from the wall and read the resistance over its terminals.

I'll try that and see what reading it give me. Interesting stuff to learn and know about for future reference that's for sure.

Thanks for the ideas and suggestions guys!