Intermountain F3A & F3B F7A & F7B F9A & F9B

Scale:
N Scale


This installation uses the following decoder:


This installation documentation is for the Intermountain F3A/B, F7A/B, and F9A/B. This installation uses the IMF4-NF decoder, and was performed by TCS.

NOTE: This documentation shows the installation process for the 'A' unit first. The installation process is the same for the 'B' unit, with the exception of the headlight wiring.

The Intermountain F7A unit shown with the shell on. Be careful as you take off the shell because it is difficult to remove and can be broken easily. It is required to remove the front coupler in most cases.
The Intermountain F7A unit shown with the shell on. Be careful as you take off the shell because it is difficult to remove and can be broken easily. It is required to remove the front coupler in most cases.
Here is a picture of the chassis with its shell removed where you can see the original Intermountain light board. De-solder both sets of wires (red and black, both front and back) from the original lighting board. NOTE: If your model does not include wires, they must be installed. We recommend TCS part number 1216 and part number 1198 (30AWG wire). http://tcsdcc.com/accessories/wire
Here is a picture of the chassis with its shell removed where you can see the original Intermountain light board. De-solder both sets of wires (red and black, both front and back) from the original lighting board. NOTE: If your model does not include wires, they must be installed. We recommend TCS part number 1216 and part number 1198 (30AWG wire). http://tcsdcc.com/accessories/wire
Next, unscrew the two screws holding the lighting board in place and remove it from the chassis.
Next, unscrew the two screws holding the lighting board in place and remove it from the chassis.
With the original lighting board removed from the chassis, next remove the two screws holding both sides of the frame together. The fuel tank can then be gently spread out and un-clipped form the bottom of the frame. Both trucks will fall out once the frame has been separated. Along wither side of the frame are copper-brass strips which must also be removed. Be cautious not to bend or flex these strips, as it is critical they fit back into place correctly. Very carefully separate the frame halves, keeping the parts ordered for reassembly.
With the original lighting board removed from the chassis, next remove the two screws holding both sides of the frame together. The fuel tank can then be gently spread out and un-clipped form the bottom of the frame. Both trucks will fall out once the frame has been separated. Along wither side of the frame are copper-brass strips which must also be removed. Be cautious not to bend or flex these strips, as it is critical they fit back into place correctly. Very carefully separate the frame halves, keeping the parts ordered for reassembly.
Shown disassembled.
Shown disassembled.
Shown with half the frame removed. If you did not have wires installed on your motor, install them now by soldering to the clips on either motor terminal.
Shown with half the frame removed. If you did not have wires installed on your motor, install them now by soldering to the clips on either motor terminal.
With the frame halves apart, use a small piece of Kapton tape as shown to insulate the motor from the frame. It is recommended to cut a larger piece than necessary, and trim and fit it using a hobby knife.
With the frame halves apart, use a small piece of Kapton tape as shown to insulate the motor from the frame. It is recommended to cut a larger piece than necessary, and trim and fit it using a hobby knife.
Reassemble the two frame halves in the reverse order from earlier disassembly and insert the track pick ups into the frame channels as shown.
Reassemble the two frame halves in the reverse order from earlier disassembly and insert the track pick ups into the frame channels as shown.
Before screwing the frame together, re-install the forward light, trucks, and fuel tank.
Before screwing the frame together, re-install the forward light, trucks, and fuel tank.
With the unit reassembled, place a strip of Kapton tape covering the chassis as shown. This will insulate the frame from the new motherboard. In some cases, excess solder from the motor wires will flow through the hole in the board creating a short. This tape will prevent this.
With the unit reassembled, place a strip of Kapton tape covering the chassis as shown. This will insulate the frame from the new motherboard. In some cases, excess solder from the motor wires will flow through the hole in the board creating a short. This tape will prevent this.
Replace the lighting board with the IMF4-NF while taking care to make sure the motor wires come through the front two holes of the decoder.
Replace the lighting board with the IMF4-NF while taking care to make sure the motor wires come through the front two holes of the decoder.
Screw the decoder in place, solder the motor connections to the second row of holes, solder the LED wires as show below, and you are ready to run!
Screw the decoder in place, solder the motor connections to the second row of holes, solder the LED wires as show below, and you are ready to run!
For the installation of the 'B' unit, follow the same steps for disassembly as in the 'A' unit including the application of Kapton tape for insulation surrounding the motor.
For the installation of the 'B' unit, follow the same steps for disassembly as in the 'A' unit including the application of Kapton tape for insulation surrounding the motor.

Important Soldering Tip

Please do not use any flux either liquid or paste on the mother board. Over time, the acidic properties of liquid or paste flux will begin eating away at the fiberglass PCB and will damage it. Use only Rosin-core solder or no-clean flux approved for electronics use.

TCS recommends the use of Kester "44" Sn63 Pb37, .015" diameter Rosin-core solder. Kester part number 24-6337-0007.

You can order this solder from the following retailers:
Digikey - PN:KE1110-ND
Techni-Tool - PN:488SO6775

Other solder tips

When stripping wire, only strip a tiny little bit of the insulation. Strip no more than a 1/32 of an inch. When the wire gets tinned with solder, the insulation will shrink back more. Try to not expose any more wire than half the length of the solder pad at most. In no case should solder or exposed wire wire ever be outside the boundary of the the solder pad you are attaching a wire to.
Click here for important information on properly Stripping and Tinning wire