Orion reports we have a potential dead block on B504, which is the block at the exit of the Stockton Station before it joins the mainline. That prevents the UP automated passenger train from running properly.

B504 is the track on the right after the turnout.

Block is controlled by a toggle on the Stockton Station Panel and the toggle appears to be properly set. The normal course of action would be to use a voltmeter and check either voltage or continuity (just remember to turn off power before doing a continuity check!):

• Check the toggle switch actually works -- I’ve had some fail on me, since, after all, some of these are 50+ years old, yet generally it’s only those actively used that fail over time (normal usure). This panel is seldom used, if at all, so I don’t expect the switch to be faulty. Anyhow, that’s easily verified with a quick ohmmeter check.
• Do a continuity check between the toggle switch and the terminal block. The terminal position we want is labeled “AW” (Approach West) on that terminal and IIRC is the left-most one (just ignore the fact the east-west direction is mislabeled on that panel & terminal).
• Do a continuity check between the terminal block and the track. In this section, the block toggles control the left rail (left rail as seen from the train’s default running direction when exiting the station). All the right rails are bridged together through a common rail “ground”.

That way, we can identify if the connection is broken, and where. Then we can narrow it down.

Schematics for the station and the terminal block. Click here for full PDF.

Remember that a continuity check can only be done when the track power is off. So if the DCC is off, set the multimeter to ohmmeter/continuity. If the DCC is on, instead use the multimeter in voltmeter mode in the AC setting and check for a ~14 V AC against any of the common rail references.

Orion did not have a multimeter at hand to check the connection. I’ll need to address that.

So instead, I suggested a crude way to check the dead block theory: bridge the positive rail gap with the previous block. A small screwdriver inserted in the track gap is enough to bridge it. Since that worked, I suggested a quick fix is to temporarily bridge the gap with something metallic such as aluminum foil or some stripped wire. And here’s the result:

That will do for now till we look at it together more closely next week-end. I also thought that this should not affect the automation -- we essentially merged B504 with the adjacent block B503a; however block B504 is not monitored and I don’t have specific timing requirements for B503a.

Update: Block B504 has been repaired. Details are available here.