MT F7 advanced information



This page has advanced tips on working on MT F7's


  • remove shell - use thin plastic shims between shell and chassis

  • remove the 4 screws holding the chassis together
  • remove the motor, truck assemblies, and the 3 "T" shaped spacers and the headlight spacer and the power pickup spacer at each end.

In the picture below notice the small plastic spacer that sits in one half of the fuel tank. Also notice the copper contacts that conduct power from the trucks to the chassis halves. They are most easily seen on the bottom chassis half, but you can see them in the top half. Notice that the left hand one in the bottom chassis half looks misaligned and bent?


The picture below illustrates the "cup gears" that are driven from the motor. Note also tie orientation of the plastic bearings on each shaft with the worm gear.



  • Remove the 4 small copper "swords" wipers to pick up power from the trucks. These look like little swords that press into the chassis halves. bend them back straight, and then use tweezers on as much as you can grasp and press them back in from the inside. Be careful.




Remove 2 screws on the bottom of the truck. Pull the sideframe casting off and pull out the wheels. Don't pull the pin that holds the 2 halves of the tower together.

Gauge the wheels and inspect. D

If you are removing the coupler, it's a good time to remove the flash from the face of the knuckle, and the face of the jaw (molding lines).

To put the coupler back in place:

  • tape the sideframe casting down

  • get the Kadee #1020 coupler tweezers, and grab the coupler, with the bent jaw on the bottom.

  • secure the tweezers with a weight on them so they hold the coupler down in the pocket

  • make sure the space for the spring is "right", align the coupler halves as necessary, push them towards the post

  • using tweezers on the last couple of loops, put the spring down in the pocket, and hold it down in place with a screwdriver

  • place the plate on top, and then drop the screw in place

  • tighten just enough to make it so the coupler does not come out

  • now pick the assembly up and tighten the screw until the free play of the cover just goes

  • test for the coupler to return to center from each extreme, if it doe not, then you have the screw too tight or assembled wrong

Chassis halves:

  • degrease and deburr

If you are going to DCC them:

  • mill out ends for decoder and lights

  • dress rectangular holes that allow
  • mill slots across tops for wires
  • use small flat ended diamond bit to clear the paint from the holes at both ends of each chassis halves (conductivity for new connections)

Pickup swords:

  • Straighten them
  • using a very small pair of needlenose, very close to the chassis, press them back through the chassis half. Push just enough to grab from the outside, don't get heroic or you will bend them.
  • These wipers will need to be straightened, flattened, and cleaned. I do this on a hard, smooth plastic surface, holding down by one end with a fingernail, and then smoothing the wiper with a flat plastic burnishing tool. Now clean the wiper by stroking with the fiberglas pen. Do both ends and both sides. Inspect.

Cleaning the motor:

  • I place the motor in a small vice that has copper foil on each jaw (plastic jaws). Now clip power to the foil and close the jaws on the brass brush holders. I shoot a squirt of Deoxit while running it at low volts, blow it out gently. Really cleans the commutator.

Cup gears:

  • glue back on, with end of shaft slightly recessed from being flush with inside of cup gear


Pickup Swords into chassis:

  • When re-installing the "swords", be sure to insert them perpendicular to the chassis. The reason is that when they are bent over to bear against the truck assemblies, they need to be parallel to the axis of the chassis, or they will not make good contact. If you don't get them "square" they will not line up properly when bent over.

  • To line them up, place in the hole, then grasp with pliers from the inside of the chassis. Now pull in when they are square.

  • Press them in with small rod or something so that they seat well, this ensures good contact between the sword and the chassis.

  • Note that the end of the sword may be recessed in from the outer surface of the chassis, don't just press them in flush.

Spacers to chassis:

  • pick one of the two chassis halves

  • add the "T" shaped plastic spacer to the fuel tank. If you did not mill for DCC, add the 2 other ones to the top of the chassis half

  • add the 2 spacers at each end. Be sure to put the one that holds the headlight in front, and the one that holds the capacitor in back.

  • If you are going to DCC, remove the capacitor

Add gears:

  • lay one gear set in one end

  • add in the motor, note the orientation:

    • make sure the hole in the motor frame is up.

    • The plastic end pieces on the motor are different, the one nearest the brushes will come off, the other is held captive by the gear.

    • Check with an illustration

  • add in the other gear

  • make sure the little fingers of the 4 bushings are in the chassis propersly



Add trucks:


Add other chassis half



DCC wiring

To add a DCC decoder, you need to mill at least one end of the chassis down to make room.



orange motor right, gray motor left

red right rail, black left rail


on the motor itself, there is a hole in the plastic brush housing that faces up..


Preparing the chassis for DCC


when drilling access hole on top, usually the the top pieces will bend down from the pressure. After deburring the hole, I used a 1/2" wide chisel bit and a punch hitting the bit to flatten it back to where it was.


F7 headlight board

  • normal wiring:
  • white wire is upper headlight
  • yellow wire is lower headlight
  • F02 (green?) is engineer side mars
  • F01 (purple?) is fireman side mars



reset decoder (use programming track only)

  • cv 8 = 8

set dimming level (use program on main, turn on headlight to confirm)

  • cv 60 = 40  (headlight will dim)

cv119 is low/high beam for f6 key

  • cv 119 = 3 (headlight back to full bright)

cv 114 is dimming mask, set to only dim headlights

  • cv 114 = 12

reverse headlight and reverse light outputs

  • cv 33 = 2
  • cv 34 = 1

set ditch lights (Mars Light Simulation)

  • cv 127 = 41
  • cv 128 = 45


and 128 to 33 and 37 respectively if ditch lights on in forward only

 zimo for the MTL F-7 headlight board


want top headlight off in fwd direction


set ditch lights (Mars Light Simulation)

127 controls FO1

128 controls F02


For ditch light type 1, set 127 and 128 to 33 and 37 respectively if ditch lights on in forward only

to set to work in forward and reverse use 32 and 36

For type 2, set 127 and 128 to 41 and 45

lower headlight is rear headlight wire (yellow).. to make it work in forwards only set 126 = 1


125 = 0

126 = 52

127 = 0

128 = 0


dim rear headlight in reverse = cv60 = 170

use dimming mask 114 to specify only rear headlight (bits 0 through 7 = 1 means don't dim that light  = 12


cv119 is low/high beam for f6 key


1 Note to ditch lights: Ditch lights are only active when headlights and function F2 (#3 on Zimo cab) are on, which is prototypical for North American railroads. The ditch lights will only be working if the applicable bits in CV #33 and 34 are on (the definition in CV #125 - 128 in itself is not enough but a necessary addition). Example: If ditch lights are defined for F1 and F2, the bits #2 and 3 in CV #33 and 34 have to be set accordingly (i.e. CV # 33 = 13 (00001101), CV #34 = 14 (00001110).


33 and 34 are 1 and 2 by default (fwd and reverse)



old stuff:

zimo programming

ditch lights
solder pads, one on edge is FO2
  one in from the edge is F01

by default fO1 is switched with function 1
by default f02 is switched with function 2

127 does fO1
128 does fO2
41 ditch light 2 right forward only
45 ditch light 2 left forward only





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