Years ago I had presented an installation for the Athearn F59PHI on my old web site and later included it in this blog as a post. In that installation I had used the original PC board that was in the engine and the decoder I used was the Digitrax DZ121 which at that time was one of the smallest decoders available.
Here is a link to that post.
Recently I was asked to replace an existing installation of a Digitrax DN121 decoder with a new Lenz Silver Mini. The PC board had been removed from the locomotive. So this post will show a different method to install a decoder in this loco that was not available in a DCC version and that no after market decoder board has ever been offered for.
The original installation is seen in this photo. On this installation, the LED's were not in alignment to get any light into the lenses, particularly the ditch lights that are on this model.
For that reason I felt there would be an advantage to having the LED's and resistors mounted on a board of some type.
This is the Lenz decoder. Notice how it does not have any heat shrink over it. That means care must be taken in it's placement so it does not short on any part of the frame. Also, the wires are more easily broken off from this decoder than those with heat shrink.
My solution to the wire problem is to place a small length of 3/16 inch heat shrink over all the wires near the decoder as shown here. This acts as a strain relief and will protect the wires being broken off from the decoder during handling.
After removing the motor from the motor saddle and marking at least one of the sides of the motor to keep it's correct orientation, I removed the little tabs that would have held the board in place if there had been one.
A stock board from an Atlas GP40 fits just right into the top of the motor saddle and with some modification it can be used as a replacement board.
I aligned the board so that the front LED is at an equal distance from the front of the frame as on a stock Athearn F59PHI. The black line across the board and saddle mark this alignment.
Notice in the photo above that the little bars on the motor saddle that go across the motor contact wipers on the stock mechanism are gone on the saddle we are using. This had been removed in the original DN121 installation. If the loco you are working with is a new installation, this should also be cut. Too see this step refer again back to the
earlier post on this model.
This photo shows the modifications made to an Atlas GP40 board to make it fit into the frame of the Athearn F59PHI.
The polarity of the front LED is reversed so that the anodes of both LED's will be tied together.
I use E6000 adhesive from Tap Plastics to secure the board to the motor saddle and then the decoder to the board. Because there is no heat shrink on the decoder, it must be placed on a spot where there is no exposed circuitry.
The white, yellow, and blue wires are soldered to the board as shown in this photo and the other wires are trimmed to 2 inches in length. Keeping them long will make it easier to put things back together.
Route the wires down through the openings in the saddle. Remove the brush holders from the motor, solder the wires to the brush holders, then after they have cooled, re-install them in the motor. Then connect the red and black wires to the contact strip. Keep the solder joints small, if needed make the openings in the saddle a little bigger.
On this model the top of the shell is removable so in this photo the installation can be seen after the shell is re-installed on the mechanism.
Several areas to to watch out for are pointed out.
Done !
