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The Randall Museum in San Francisco hosts a large HO-scale model model railroad. Created by the Golden Gate Model Railroad Club starting in 1961, the layout was donated to the Museum in 2015. Since then I have started automatizing trains running on the layout. I am also the model railroad maintainer. This blog describes various updates on the Randall project and I maintain a separate blog for all my electronics not directly related to Randall.

2021-07-06 - Repair for Turnout T450

Category Randall

The Bridgeport turnout needed fixing, and it is now fully functional again.

It uses a Fulgurex turnout, and recently this one had started shorting the entire turnout power supply intermittently.

This is a Fulgurex slow-motion motor. Connections have two wires for turnout power, and two sets of contacts (three wires each) that are commutated based on the position of the switch:

And here it is after the fix, when testing it:

As typical on this layout, the connections go to an intermediary terminal block, which makes it easier to unplug it:

On the bench, before fixing it:

Testing it on the bench, it draw twice more amps in one direction than the other one, and the motor seemed “reluctant” to move sometimes.

So how does one go about fixing a Fulgurex? Well I happen to have a left-over box from the GGMRC years full of mostly dead ones that seem like they have been removed from the layout (probably when they changed a good part of the mainline to Tortoise). Which means not quite dead. I think some of them are quite good. I carefully looked at many:

And here’s what I’ve noticed:

  • Some are missing the motor screw gear.
  • Some are missing the motor.
  • Some are missing the little spring that make the contacts click. These are used for the layout aux (top contacts) or the motor end-of-course (bottom contact), which means a single missing spring makes the whole assembly useless.
  • After close examination, the motor is held in place by 4 plastic clips, which means it’s trivial to change the motor.
  • And I found a couple motors in my box.

.

Based on this, I decided the most likely easiest way to fix this would be to swap the motor. I selected a motor that looked almost as good as new and seemed snappy when tested with the bench power supply with no load at all.

Here’s it after fixing and testing it:

For reference, terminal block wiring, from right to left:

Bottom row (to layout)

Top row (cable to Fulgurex)

Green - 12V DC turnout control

Green - to motor power

White - 12V DC turnout control

White - to motor power

Red - DCC

Blue

Orange - to frog power

Pink (Normal: to blue; Divergent: to Gray)

Black - DCC

Gray

3 wires going to a remote terminal block.

Likely for the signal on top of Tehachapi loop.

Yellow

Red (Normal: to Yellow; Divergent: to Orange)

Orange


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