Kit: MX644C; YouChoos Flame10 or IceCube18X13X10-1W speaker
Bachmann's Class 90 electric model is a UK first, with working servo-driven pantographs and a host of lighting options. It is
designed for a 6-function MTC decoder, with additional servo outputs - perfect for the Zimo MX644C. YouChoos have developed a
project specifically for this model, with control for all of these items out-of-the-box, as well as a dedicated sound project.
Locate the 4 screws on the underside of the locomotive, carefully remove them with the bogies slightly turned. Take care not
to damage the pantograph or the aerials on the top of the locomotive.
Another 4 screws further toward the centre also need to be removed.
Once the body is removed, carefully lift out the top cover to gain access to the decoder. Extract the blanking plug, ensuring
it is lifted evenly to avoid bending any of the 21 pins.
Insert the MX644C, ensuring it is the correct way up and carefully line up all 21 pins. Whilst installing the decoder, avoid
crushing the wires that run along the side of the 21 pins.
Bachmann have pre-fitted a SugarCube speaker, so there should be no need to add your own.
Once the decoder is installed, test the locomotive before replacing the top. Once tested and proved the locomotive is
operating correctly, place the top back in position, replace the screws underneath and tighten, but not so tight as to strip
**** WARNING: REMEMBER TO UNCLIP THE PANTOGRAPH BEFORE YOU USE THE LOCOMOTIVE, This will avoid damage to the pantograph
Having tested the locomotive for sound we found that the pre-fitted speaker vibrated considerably, therefore we decided to swap
it for something bigger and better...
Once the body has been removed again, unplug the three plugs - one for the pantograph servo and the other two for the cab
lights. The speaker is mounted on the top of the body, therefore remove the two screws holding the circuit board in place, and
prise the speaker out of the casing.
Cut the two black speakaer wires close to the circuit board and solder them onto the new speaker (It does not matter which way
round the wires go).
Clean the chassis inside the hole, then place two small blobs of Black Tack either side of the prop shaft, and finally place
the new speaker (metal side up) in the gap as shown. Our example here uses a Flame10, which is a pretty good fit for the
aperture, but an IceCube18X13X10-1W would also work very well.
Take the rest of the excess wire and loop it to the side of the speaker and place a piece of insulation tape over the top, to
give it a little protection.
Now take the body and carefully cut down the speaker housing to about 2mm from the top of the body using a drill and milling
bit. You will then need to clean around the edges with a knife.
When you are happy with the finish, reattach all the plugs and place the body onto the chassis, then replace the 4 screws,
remembering the short ones go in the front and rear, the longer screws go in the middle under the bogies.
That's it - you're ready to go! The YouChoos configuration of the MX644C decoder should work out-of-the-box with all of the
Class 90's lighting and the servo-driven pantographs.
Photos and words kindly provided by Robert Train of Robert's Railway Repairs, who is one of our longest-standing
accredited service/fitting partners.