Greg's web site!

USA trains EMD F3

General: 

These are nice looking, well proportioned locomotives. They are available in 2 road numbers for Santa Fe red warbonnets, with the prototype ABBA "LABC" numbering, L=lead, AB are B units, and C is the trailing A unit. They run well.

Earlier units have a small square "pancake" smoke units, and these burn out if they run out of fluid and are not great. The newer units have fan driven smoke units that work very well and have low fluid shutoff.

The wheels are 1.126" measured next to the flange. This scales out to almost 33" in 1:29. Mid-tread, the wheels measure about 1.110" diameter, flanges about 0.12".

Body General:

The first thing I noticed is that you need to be careful how you pick them up! If you do what I did, your fingers will either stress the nice grillwork on the upper sides, or you will hear a "pop" and "klink" as a clear plastic window pops loose and rattles around inside!. The windows in the doors are also not well glued in, and you can also dislodge the doors easily.

Pick it up by scooping it up by the "belly" / fuel tanks. Keep your hands off all the nice detail!.

Trucks:

To remove and replace the sliders, you need to remove just the bottom cover screws. Resist the temptation to remove the sideframes, it helps keep the wheelsets in place. You do have to remove them to remove the wheelsets.

When you remove the gearbox cover, the brass axle bearings will pop out. They are squared off, and go with the sides up and down. Of course as soon as they get loose, they turn 45 degrees and won't go back in. Put the sideframes back on first, then with a little prying up of the wheelset, align the bearings, and then the gearbox cover will go back on. If it does not pop back in place with light finger pressure, the bearings are not in right. Take the cover off and do it again.

Kadee Couplers:

Both the A and the B unit use pedestals to mount the couplers. You need to remove the pedestals with 2 screws, and then remove the stock coupler. You trim the end of the swivel "tang". Cut it just behind the round end at the tip. Use the standard 831 coupler, but you need to trim the end of the silver screw before you assemble it, otherwise the screw is too long, and sticks into the pedestal, and the coupler won't swivel. Note that the swivel "tang" is thinner on the A unit pilot, so your screw trimming needs to be more accurate. Trimming the screw gives you thicker thread diameter through more of the "tang", thus more strength.

The Kadee site says you need to do something special to the pilot on the A, but I used the same procedure. Be sure to re-engage the centering spring/wire into the little hole in the back of the swivel "tang".

From the Kadee site, you will probably want to make little "L" brackets to limit the travel of the coupler, they do swing too much from side to side, although running around corners and backing on my 48" diameter test loop has been no problem so far, but it looks bad at the minimum.

Wiring for DCC

The trucks have 2 sets of wires that come from each truck. They go to black 2-pin connectors and then to the circuit board. The connectors for each truck are opposite sex, so you cannot plug the wrong ones together.

The connector with 4 wires is the motor, and the one with 2 wires is the track power pickup. Since the motor is already isolated from the track pickup, these can be easily wired to the decoder. I pulled the wires from the circuit board, so I could unplug the trucks for maintenance.

There are 2 boards in the chassis, one is the primary power board, and the other is a regulator board for the smoke generators.

On the main board, there are 2 connectors for lights in the cab, number boards, leds above the number boards, and the 2 headlights.

The 2 pin connector gets track voltage, and is connected to the 2 bicolor leds just above the number boards. The wires are black and white. If the white lead is positive, then the leds are green, and if the black lead is positive, the leds are red. There must be a current limiting resistor on the small board in the nose of the F unit. At 20v DC, these drew 57 ma. OK, so fine, my AC is 20v rms. Hooked it to the decoder directly, 57 millamps, great.

Now to the cab lights and headlights.

The 3 pin connector uses the black wire for common, the red wire powers the cab and number boards, these are GOW, and I reversed the polarity to them, they still lit. (means no regulators or diodes on the circuit board in the nose to these). These were supplied a regulated 3 volts from the original circuit board. They drew 135 ma at 3 vdc. This would require a 126 ohm resistor at 2.3 watts.

The headlights are GOW also, and were supplied a regulated 3.57 volts (in the forward direction only) from the original circuit board. At this voltage, the 2 bulbs drew exactly 100 ma. That would make a 164 ohm resistor at about 1.6 watts.