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Replacing A Fried Circuit Board In A Repro Dorfan 3930 Wide Gauge Crocodile

By Jim Kelly-Evans


The wide gauge Dorfan 3930 in black was catalogued with freight cars in a set called the "All Star Freight Limited," set No. 894. I purchased a reproduction locomotive a few years ago to pull my original Dorfan wide gauge freights. I was happily running the set at an Standard Gauge Module Association event when the locomotive began to smoke and stopped running. A quick inspection on site revealed a hopelessly fried circuit board.

You can see the damage to the components after the event.

The loco sat in a box for a couple of years patiently waiting for repair. I finally got around to working on it after I saw a recommendation on the 0 Gauge Railroading forum for the reversing boards made by Dallee. I ordered the 12 amp version that Dallee offers. Installation proved to be easy once I figured out how to mount the board in the locomotive chassis.

The repro croc chassis halves have mounting slots for the manual reverse switch forward and spare slots aft that are not used. I don't know why they made the castings this way but I'm glad that they did. The Dallee board contains a large rectifier chip the base of which has to be mounted to the locomotive chassis directly for heat dissipation. Unfortunately, there is no place to do this on wither half of the croc chassis. The solution was to cut a piece of perforated steel stock and make it the same size as the reverse switch board. This steel plate would hold the Dallee board and mount in the spare set of slots in the loco chassis.

Silicone-based grease insures good heat dissipation

The Dallee reversing board sits on its own steel base which is held in place by the slots cast into the locomotive chassis.

There is ample clearance side to side and plenty of air space above the board.

The reversing board sits nicely in the chassis with the locomotive halves re-assembled

The story has a happy ending as the black 3930 is once again pulling Dorfan wide gauge freight cars on the layout.

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