|[an error occurred while processing this directive]|
Fitting a Digitrax DZ121 into a Roco HO
Scale DR BR41 and BR50 (they use the same tender)
Author: Steven Skinner
This is intended to be a step by step tutorial for the uninitiated. Please don't be offended if sometimes I state the obvious as newcomers sometimes need detail that more experienced people do not. If you are experienced then skip the finer detailed instructions. First timers, do not be afraid. Take everything step by step and you will be just fine. If you come across a problem, or do not understand anything, Please do not hesitate to email me.
The Digitrax DZ121 is the most suitable decoder for these locos because of its small size and enhanced capabilities (see Digitrax Specs).
First, sit down at a suitable bench/table with a white piece of paper and the loco in front of you.
The paper is for putting all the small parts on and you can write where they go!
Separate the Loco and Tender by pulling gently with all the wheels on the bench therefore voiding twisting the drawbar. Put the loco back in the box for now.
Turn the tender upside down (in a foam cradle if you have one) and remove the two crosshead screws from the baseplate. DO NOT LOOSE THE SCREWS! Then holding the body and chassis together, turn right way up and put it wheels down on the table (if you don't, the motor will fall out). Remove the body and put the chassis to one side.
Remove the plastic coal holder from the top of the cast metal tender body by pulling. there are two hidden pegs inside the moulding force fit in two holes drilled into the casting so don't twist it you may break them off. If you wish you can remove the plastic ladders too so's they dont get broken at the next step. Between the two holes we need to remove enough metal to fit the decoder and the harness. I used a milling machine but a hacksaw and files will do. Tip, hold the body in a soft cloth in the vise jaws so's not to damage the paintwork. DO NOT RUSH THIS JOB! you will damage the paint!
The most important aspect of decoder installation is insulation of the motor brushes from anything but the decoder output. This is what we are going to do next. Gently lift out the motor from the chassis noting its orientation(fit) and put it back so you can see how it fits.Don't worry about the brass tang for now, we are going to remove it. When you are happy you understand where it goes, put the motor in front of you and put the rest aside.
Identify the brush holder with the red square washer under it and remove the hexagonal nut carefully. Pop out the retaining spring and motor brush and remove the brass tang.Discard the tang. Reassemble the brush, spring and nut in reverse order. This side is finished.
On the opposite side, again remove the nut, spring and brush, but this time there is a small brass washer. Discard the washer, but do not reassemble yet.
Grab your 20 thou plasticard and make a white washer exactly the same as the red one on the other side. Reassemble as before.
Continuity test that the brush holders are now both insulated from the frame of the motor. If not then suspect your new white washer first. Go over the modification carefully until they are. Check the motor spins freely and put aside. The motor modification is now finished.
[ last updated 31st Dec 2003 ]