Kit: Zimo MX645 (hard-wired) with SugarCurve8 in boiler; YouChoos SuperCap6800uF stay-alive (in bunker); SMD firebox glow LED; weathered crew
Donor model, pretty much the same as the 42XX...
Pop the top off, revealing 8pin DCC socket at the front and a little room in the boiler. Got to avoid that fly-wheel when routing wires.
Cab roof clips off very easily, so good access for inserting crew and other things...
Drill a hole for the SMD firebox glow LED, and create a shallow channel for the wires to sit in, to avoid snagging later when
the body goes back on.
The plastic frame comes off fairly easily too, making it simple to get access into the boiler and bunker.
Drill out enough space in the bunker for a SuperCap6800uF
Boiler is perfect fit for MX645 and SugarCurve8
Wire up the SuperCap and cover in electrical tape to protect (case of the cap is -VE connection, so mustn't touch anything metal!)
Drill small hole in back of cab to feed SuperCap wires through, along cab floor and out the hole where the firebox glow LED will be.
Glue in the SMD firebox glow, right into the hole and route all the wires (LED and SuperCap) together down the channel we made earlier.
Add resister on +VE (blue) wire of firebox glow LED.
Join everything up
MX645 goes highest in the boiler, with SugarCurve8 slotted in just beneath it - just fits. I usually cover the speaker with some
thin double-sided tape before slotting in, so it doesn't move around.
Add some dirty crew, paint the SuperCap wires on the cab flow with black acrylic, pop the roof back on (tiny dots of glue to secure
if necessary), add some lump coal in the bunker, and we're done!