Illegitimate power feed!?

[centenary]

I think I have what's colloquially known as a 'bar steward feed' in one of my DCC power districts that is affecting an isolated track section.

Ive wired a DCC Concepts IP Analog point motor to switch off \ on the dcc supply to a section of track in front of a point. I tested the input and output of the dcc supply before soldering the relevant wire to the track. When I operated the IP A, the internal switch completed the circuit when the point was set for straight ahead and disconnected when set againt straight ahead.

Great! This is what I wanted.

I decided the red wire will power the cut, isolated rail. I soldered the (red) dcc supply from the switched side of the IP A to the rail then made an isolation cut in the same rail. The isolated length of track is now wired as follows: black rail continuous with the other rail, two red droppers with an isolation cut between them. Only the dropper in the isolated section of track goes to the IP A. This set up should cause the loco to stop once it crosses the isolation gap and the point is not set straight ahead. There's no stay alive in the loco.

When I set the point so it isnt straight ahead, there should be no power to the isolated section but there is and despite testing the switch operation previously. The loco doesnt stop and power is confirmed via my multi meter. Throwing the IP A to straight ahead or the diverging route still shows the isolated track with power!

There's only the one red dropper to the isolated rail and section. There's no other direct connection between the isolated section and the point rails. I dont use rail joiners and there's a small expansion gap where I can see clear separation.

It seems Ive a 'bar steward feed' to the isolated section? What's the best way to try and track down where this is coming from?

Hope Ive explained this clearly. I have wired roads in the storage yard the same and they switch off \ on power correctly.

[RFS]

Do you not need two isolation gaps - one next to the frog and one at the other end of your selected dead section?

[centenary]

Do you not need two isolation gaps - one next to the frog and one at the other end of your selected dead section?

Hi. No, because Im using Peco Code 75 Unifrog points. You dont need insulated rail joiners because the frog is isolated out of the box and all routes correctly powered.

However, I have sorted it. I dont know if this is an effect of DCC but, it appears power was crossing the isolation gap on the red dropper rail! I had disconnected the red dropper on the isolated section of rail & track from the dcc supply so there should have been no power across the left and right rail. But there was when tested with the meter and loco!

Admittedly, the isolation gap was only the width of track cutters 'cut' and I could see clear separation. That got me thinking was the gap too small and daft as it sounds, was the dcc power arcing the gap?

This time, I cut a bit more of the red dropper rail so the gap was about 2mm. Re check with the meter and now there was no power at all to the isolated section of track!

Restored the dcc power to the layout and tested all 3 points combinations. Success! All locos now stop short of the points as desired instead of crashing into them and causing shorts if the route isnt set for them.

I appreciate some might say should have used insulated rail joiner instead of relying on gaps. Unfortunately, Peco dont make specific IRJs for Code 75 bullhead. They suggested using their standard IRJ cut down but I found these didnt hold the bullhead track to my satisfaction.

[RFS]

Glad you've sorted it. Without IRJs there's a small risk that hot weather will cause the rails to expand and contract, and eventually touch. That happened to me once and it took a long time to track it down! You could prevent this by filling the gap with Araldite or similar so it can't close up.