Chipping the Alco F units

I mentioned before that I had ordered some Southern Digital frames and Digitrax DZ126 decoders for the FA1/FB1 loco set that I want to put DCC in. I only ordered two frames, enough for one set, just in case they didn't work out. I could have gotten DZ123 decoders a bit cheaper, but the 126 has BEMF and better motor control, so the added cost was more than justified.

They arrived and I set to work to put them together. I'm happy to say they worked out great, I did make one modification that I will show to connect the wires and I did have to deviate from the instructions a bit for the motor wire length, but overall they were well worth the purchase price.

The first thing I did was strip down one of the locos and compare the frames.

 The left half of the frame is virtually identical to the stock frame, about the only difference (not pictured) is the tab that contacts the upper motor brush is missing on the Southern Digital frame. The right side is very different, having the relief cut out for the decoder. The pocket that the motor fits into is also deeper to allow room for the decoder wire to run to the bottom brush. This becomes important when modifying the stock frames to use on the B units.

I assembled one of the frames as per the directions and discovered that the decoder wire lengths that are specified are too short for the motor leads, they both needed to be another inch longer than the instructions said so that they would reach to the relief where the decoder sits.

The instructions also said the white magnet on the motor went to the top, but both of my motors had the white magnets on the bottom. I left the white magnets on the bottom and when I was done the locos went forward when the NCE PowerCab had forward selected and backwards when the PowerCab said reverse, so they must have been right.

The second thing is the way the wires connect to the frame. The directions say to solder the wires to the frame, but I found the solder just would not stick to the frames. So I figured out another way to do it.

On the left half there are indents cut in for some brass clips to fit in, these clips hold the plastic bearing blocks for the worm gears in place. Being brass they were easy to put some solder on for the black decoder wire.

I had noticed some indents down the sides of the frame and thought maybe the red wire would fit in the one closest to the rear of the frame. I checked, and sure enough it did. So I took my rotary tool and a cutoff disk and cut a wire channel in the top of the frame.

Next, I inserted the truck pickup strip into its spot on the right frame half and marked it where the slot in the frame was. Then I tinned the contact strip.

With the contacts figured out I soldered the wires to the motor, put some electrical tape in for added insulation, and put it in the frame with the gears.


The frame was then reassembled and the black and red wires soldered to the frame tab and truck pickup strip respectively.
 

 The red wire was then tucked into its new slot in the frame;

 and the decoder was nestled into its new home.

The trucks were put in and the headlight wired up to the blue and white wires. The directions say to just hook the white wire up but I did them both.

A note of caution, if you ever do one of these be sure to cut the traces on both sides of the light PC board. They are both connected.

I then put the assembled loco on the track and tested it out, and it all worked swimmingly. This completed chassis then went under one of the A units.

I then took a close look and noticed that with a bit of judicious filing the old frame would work for the B unit, I just had to take off enough material for the decoder to fit in the depression where the cab would be on the A unit. I used a rotary tool and cutoff wheel to accomplish this. I then cut a slot for the red wire, on the front of the frame this time, and then while holding the frame halves together cut a slot along the spine of the frame from the front to the top motor contact tab to clear the motor wires. Lastly I cut out the top motor contact tab on the left frame half.

With these modifications the decoder fits on the front of the frame with no problems. The light wires were just clipped short and taped off. The contacts were soldered on the same way as before, and the finished locomotive was tested and put under a B unit shell.

That left me a spare Southern Digital frame. As luck would have it I had another set of locomotives to modify, so the work was done and I now have not one but two FA1/FB1 sets in Erie paint.

All I have to do now is speed match them and I'll be all ready to go pull some freight.

UPDATE: When I went to speed match the locos I found the chipped units were much much slower than the non-chipped units. The non-chipped units ran a max of about 106 scale MPH (prototype top speed was about 65) while the chipped units were fortunate to find themselves above 35. I took the units apart and found the decoder wires were causing the motors to bind on the modified stock frames. So I had to cut a relief in the modified stock frames for the decoder wire and I also had to adjust the tightness of the screws holding the two frame halves together. The screws have to be tight enough to hold the frames together to slip inside the shell but no tighter otherwise the motor binds. Screw tightness also accounted for the slow speed of the Southern Digital framed units.

With those adjustments and modifications made the chipped units once again ran at the same excessive speed as the non-chipped units. I set CV's 2, 5 and 6 on each  individual unit to give each loco a starting speed of about 2 scale MPH with a top speed of 65 and a mid speed of 35. Now they all run together as they should.

I now have four chipped units and two DC only units. I'm thinking of selling the two DC units because they have the same numbers as one set of chipped units, but I may just keep them for DC only operations.

But I have them all the same.