Just finished doing a HO Spectrum Pennsylvania K-4 Pacific Steam Locomotive by Bachmann.

Thought may be some of you might be interested in how the DCC conversion went, as well as adding a Starr-Tec Chuffer.

The full stall current for this loco is 900 ma. I selected the Digitrax DH140 for this loco, with it's 1.5 amp rating, it should be fine for both the motor and driving the Chuffer.

To remove the shell, turn the loco over, in the center of the post for the draw bar you will see a screw and a small metal washer with two ears to hold the draw bar on. Remove the screw and washer. Now lift the shell up from the cab end and slide forward and lift off the frame. If you look inside the shell you will see a PC light board, this and the 1.5 volt head light seem to work fine, so I decided to leave it as is and not used the decoder to power the headlight. No directional lighting, but does stay lit in both directions.

You will notice the loco has a typical split and insulated diecast chassis. One thing that is not typical of this loco, is that unlike most steam locos it has all wheel pickup on the loco and the tender just goes for the ride. I guess one could say this is a DCC friendly loco..<G>

Now comes the hard part, removing the motor so we can isolate the brushes. At first glance this does not look like to bad of a job. If you have the exploded view from Bachmann it will still look like a fairly easy thing to do. That is till you find out that the exploded view does not tell you what is glued to the frame. The steam cylinders and parts of the valve pivots are glued to the chassis and would have to be removed to completely separate the chassis. But fear not, I found a way to get the motor out without having to completely separate the chassis.

Notice the white tape down each side of the chassis, remove it and throw it away. This will expose two screws going through the chassis, one at the rear and one up front. Remove both screws and the plastic insulator nuts they screw in to. Notice that where these screws go though the chassis between each half of the chassis there are two contact plates and a plastic insulator between them at each end of the loco. The contact plates have wires going to each, these are the wires from the trailing and pilot trucks for each side of their pickups. Take a small flat bladed screwdriver and insert between the chassis halves, and pry apart the top half of the chassis, and with two fingers grab the contact plates and insulator and slide out from between the chassis halves.  Note which contact plate is on which side of the insulator and also note how they mate together with the pins on the insulator. If you cross these contact plates you will have a direct short across the rails when you put it back together. Now do the same for the other set of contact plates and insulator. Now turn the loco over again and notice the two screws in the center of the chassis underframe, they are located between the drivers, remove these two screws. Now comes your choice here, if you want to break the glue joins on the steam pistons and the valving pivots you can completely separate the chassis by completely removing the underframe, drivers, valves, pivots, and gears. Or you can just pry the back of the underframe down, do this by placing a flat bladed screwdriver between the underframe and chassis just under the firebox area. This will allow the drivers to drop far enough, so you can separate the chassis halves just enough to let you get the motor out. Do this by holding the loco upside down, take the screwdriver and pry the frame apart like you did for the contact and insulator plates just in front of the motor and worm gear, hold you hand under the motor and shake a bit, it will fall out in to your hand.

With the motor in your hand, cut off both the long tabs that are used to contact the chassis halves. Leave just enough to fold back over the brush holder. Notice the arrow on the side of the motor, this will go down when you re-install the motor. Noting that, solder a wire long enough to come up along side the motor to the bottom brush tab. Place a piece of electrical tape over the solder joint so it can not contact the chassis. Put a drop of Areo-Car motor bearing lube on each of the motor bearings, and a drop of Conduct-a-Lube on the commutator. Now just pry the chassis apart again and drop the motor back in, arrow down. Pop the sub frame back up in place and re-install the two screws back in the sub frame. Remember how those contact plates and insulators were assembled, put them back together and insert back between the chassis halves. Put the screws and the insulated nuts back in the chassis. Take a ohm meter and check the motor to be sure both brushes are isolated from the chassis, also make sure you got the contact tabs on the right side, do this by checking a again with the ohm meter and makes sure the right wheels of both the trailing truck and pilot are connected to the correct side of the chassis halves. Now remember that white tape we tossed out, replace it with a piece of electrical tape down both sides of the chassis, this is to keep the grab rails from shorting out to the chassis halves. If all checks ok we are ready to install the decoder. But test the decoder first.

Now where do we put the decoder, either in the loco or the tender. Well if you notice, there is no room in the loco for it unless we cut the frame. This loco is in need of more weight to start with so this is not a good idea. Also by installing the Chuffer, there is going to be a min. of four wires going between the loco and the tender no matter where the decoder goes. So I selected the tender. Besides the wires on a Digitrax Decoder are small and flexible any way. To open the tender, look on the bottom just behind each truck remove the screws and lift the shell off. If you are just going to install the decoder there is plenty of room, just tape it down and run the wires out to the loco. But if you are going to install a sound system or chuffer as I did you will have to remove things from the floor and shell, posts ,ect to make room. I installed the speaker in the floor, just to the rear of center, cut out what ever was in my way, and removed as much of the floor as I could in the area under the speaker, without removing any of the detail on the under carriage, then glued the speaker down with some silicon. While you have the silicon out, if you hold the tender shell up to a light while looking inside it, you will see a few areas that are not sealed. Seal these with silicon. The idea is to make the tender sealed as much as possible to improve the sound. Next just in front of the speaker I double sided taped the decoder to the tender floor. Cut a small notch out of the floor front, just big enough to feed the decoder wires out to the loco.

The Starr-Tec Chuffer I used uses motor voltage to sync the Chuff, and uses a 9 volt battery for power when there is not enough voltage going to the motor.. The Chuffer draws 50 ma from the motor leads and 20 to 70 ma pending the volume setting from the battery. It can be used on both AC and DC systems. The input from the motor is through a rectifier so we can hook it right to the motor leads, and there is no need for the 9 volt battery, we have functions on the decoder for that. <G>. There are two controls on the Chuffer, volume and sync. This Chuffer fits real nice over top of the speaker and the decoder. Just be sure the adjustments are under the coal portion of the tender shell, there is more height here for them. Just splice the two input wires one to the decoder gray wire and the other to the decoder orange wire. Inside the tender so the remainder of the orange and gray wires can continue out of the tender to the loco. Now remove the 9 volt battery clip and solder the red wire to the decoder blue wire, and the black wire through a 47 ohm resistor to the decoder green wire if you want to use function one. Feed the gray, orange, black and red wires from the decoder out through the notch you made earlier, coil up the rest of the decoder wires and tape out of the way.

Now back to the loco, the sub frame extends out under the cab beyond the chassis, just behind the chassis is a good place to drill a hole big enough to feed the decoder wires up through. Feed the gray, orange, red, and black wires up though the hole. Solder the red wire to the right contact tab on the rear of the chassis, and the black to the left tab. Be carefull you do not melt the insulator between the contact tabs. Solder the gray wire to the top motor brush and the orange wire to the wire you solder to the bottom brush. Use heat shrink tubing on all splices.

Once this is all done, you are ready to put the loco on the program track or PR-1. If you can read the factory defaults, everything should be Ok and you can program it up and put it on the layout. If not find out what is wrong before you put it on the layout. You can put the loco shell back on, slide the front over the frame, then slide it back to hook the front on the frame. Push the back down over the frame and replace the metal washer with tabs and the screw back into the draw bar post. For now leave the tender shell off. Hook up the draw bar and set the loco and tender on the rails. Set the throttle to the address of the decoder and if all is well it should start to move in the desired direction. At this point you may or may not have chuff. Turn on function one and read the directions for adjusting the volume and syncing the chuffer. Play with the sync control till you are happy with it. Once you are happy with the sync adjustment and volume, put the tender shell back on and enjoy your new loco.

NOTES:

<about the Starr-Tec Chuffer.>
It gets it's power from the motor leads and needs to have at least 5 volts to work. The 9 volt battery, or in our case the function lead, is only there for when the motor is being supplied less then 6 volts.
 

<couplers>
KaDee number 4 for pilot, 37 for tender.

<firebox flicker.>
There is enough room for a couple of small lamps between the back of the door and the chassis. Just feed the needed wires
out from the tender and set the FX on the function leads. Drill a few small holes through the door and a couple on the underside of the sub frame.

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