This installation is for Micro Trains line Z scale GP35 and features the MZA4 decoder.

Important note!

Recently, Micro Train changed the chassis design and our MZA 4 decoder will no longer fit into new locomotive releases (including GP35).

Click HERE for more informations.

In case of any questions, contact or call (215)-453-9145


The pictures and information below is for the earlier chassis version only.


              Remove the body shell and handrails by gently pulling up on the shell. ┬áRemove the fuel tank.

First, using tweezers, remove the two springs located on either side of the Locomotive ( take care not to crush the spring's coils ) then slide the original lighting board out.

Above is pictured the Locomotive's chassis with its shell taken off and without the original light board. Loosen the six (three on each side) screws( circled in red) holding the frame halfs together about one turn, but do not remove the screws. Just slightly spread the top half of the frames apart, but do not take them completely apart. Spread them just enough to fit the MZA4 decoder between the post.


Gently fit the MZA4 so that all four decoder contacts (circled in red) contact the four chassis posts. Track power connection to the decoder is achieved by a pressure fit between the frame post. Do not attempt to slide the decoder into the slots in the posts the way the original board was. The decoder should be level with the slots but not in them. After the decoder is in place re tighten all six screws.


Attach the half-circle end of the spring to the decoder, and the semi-circle side to the motor tab. Follow spring direction as shown in the photo above.


This pictures shows electrical contact between the MZA4 and the frame.


Optionally we recommend using Magnet Wire to replace the "hard to work with" springs that come with the Locomotive.


Here is the picture of MZA4 decoder installed using Magnet Wire