Modeling Notes: S-Helper Service - F3

Product Review

(photo © S-Helper Service)

Bob Hogan did a product review of these engines in the November/December, 2001 issue of the S Gaugian magazine.


This model won the "S Scale Locomotive of the Year" in 2001, as voted on by the readers of Model Railroader magazine.

Lights Warning!

Don Thompson warns to not plug DCC decoders into this engine without dealing with the headlights first. The headlights are 5-volt bulbs, and they will blow as soon as the decoder receives power (usually around 12 volts). One option is to consider replacing them with LEDs and a matching resistor. The same applies to class lights, numberboards, and Mars lights, as applicable.

MU Cables

MU cables between these engines only synchronize the motor current; they have no effect on the sound of the engines.


Don Thompson says that to remove the shell, remove the four corner screws, and then wiggle the shell. Put a small screwdriver through the back door on the top of the floor to release the rear of the shell first.

See this web site for information about how to disassemble the engine's trucks. The F3 is done the same way as the NW2, which is shown on the site.

Locomatic to DC

Converting one or more engines with Locomatic factory-installed to a plain DC version requires the removal of the Locomatic unit and adding a DC-shorting plug to each of the engines. The MU cables are then no longer needed. Test each unit individually for proper starting direction (if running in a multiple-unit consist).

Locomatic to DCC

Converting these engines with Locomatic factory-installed to DCC, S-Helper Service used the QSI Revolution U F3A decoder. It provides the slightly higher power that the engine needed, and it also supported the 5-volt supply for the lights. See these supplemental documents:

Installation Document (PDF)

Installation Diagram (JPG)

DCC to Locomatic

You will need the Locomatic board specific to the F3. Do not use the Locomatic board of an F7, as they are not the same. For multiple-units (MU) hook-ups, you will need two sets of MU cables to connect between the engines. An alternative to the MU cables is to find an F3 Locomatic board for each engine in the consist. Don Thompson recommends only using the 10-button controller, because otherwise operation of the engines is not ideal. His advice is that since these are parts created around the year 2000, it might be cheaper and easier to buy a DCC system than to try to find the Locomatic boards, unless you already have them.

Sound Decoders

The original sound decoders were manufactured by Soundtraxx. Don notes that these boards had two tiny circuit-breakers that would be triggered any time more than 12 volts was applied to them, and they would require a reset by Soundtraxx.

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