Original C-16

We're did a QSI install on R.J.'s "original style" C-16. This is without an Aristo socket.

To disassemble the loco, you remove 3 screws, one on each side of the cab, and one long one through the steam chests into the smoke box.

Here's some pictures of the wiring in the loco:

The wiring is very simple, there is a small switch that lets you turn off the lights and smoke. It is a center off. Off is off, one way is lights and smoke and motor, the other way is lights and motor.

Notice the 4 pin plug and socket for the motor block hanging in the air between the chassis and the shell.

There is a bulb that lights the firebox, it's on the red wires, partially hidden by the chassis.

There is a pair of black wires heading off to the back of the loco and will connect to the tender, the standard 2 pin "JST" style connector Aristo uses on most of their locos.

There's a bunch of wires that go back up into the shell, this is for the smoke unit, the headlight and the marker lights.

The picture below shows the switch and wires in detail:


The this picture below shows the back side of the switch and circuitry:

So, using the above pictures we define all the wiring:

Track pickup and motor:
The group of 4 wires that are black, brown,  blue and black are the wires from the plug on the motor block. The black wires are the track pickups, the blue and brown wires are to the motor. (read the section below, sometimes this is not true) On the plug, the black track pickup wires are the outer 2 wires, in J4.

Ashpan light:
This is an incandescent bulb operating from track voltage, and is connected to the pair of red wires. Both wires are in J5

Smoke unit:
There are 6 wires left, the pair of black wires go to the smoke unit. One of these wires is in J2.

These are the 2 white wires, it is an incandescent grain of wheat type of bulb, running from track voltage.

Marker lights:
These are the 2 blue wires, one is in J3.


You can see from the switch and circuitry that one of the motor leads is always connected to the track pickups. This is the blue wire. You can see this by the trace between the blue wire and the black wire in the picture. For DCC or other conversions this connection must be broken. The simplest solution would be to unsolder the motor leads from everything else. (Note, read below about potential problems).

You can see that the healight and smoke unit are enabled by the switch, and the motor is connected in either direction. Only the smoke unit does not function in both "on" positions.

The headlight and marker lights and the ashpan light are all connected to the rails.

The 2 black wires at the bottom of the board go to the tender to connect the track pickups from the drivers to the tender pickups.

The centers of the wheels are insulated/plastic, so there are "clips" that connect the rims of the wheels to the axles, see the little finger touching the rims here?

Pictures of the tender. RJ had added a Sierra sound system, which will go in favor of the QSI and the magnet will go too. Just behind the man, you see the wires from the tender wheel pickups come through the floor, 2 black and 2 brown:

Note the front truck has 2 brown pickup wires and the rear has 2 black wires. Whatever happened to polarity?

Ok, so on to wiring.

First we removed the brown and black motor leads, and extended them back to the tender, using another JST style connector. (RJ will eventually get a 6 pin connector to use between the loco and the tender).

Test these 2 leads by applying DC power, make sure the motor runs.

Now you need to check the track pickup leads. Leaving the tender disconnected from the loco, check and identify which leads are to the firemen's side and which are the engineers side. Try the wire for the engineers side, make sure you have good conductivity with a meter (under 10 ohms) to the 2 wheels on the engineer's side.

Do the same for the fireman's side. Now make sure there is NO conductivity between these 2 wires. Label/identify one wire as engineer's side and the other wire as fireman's side.

Now connect the locomotive using the existing 2 pin JST connector.

Again, from the fireman's side wire you should only have connectivity to the 4 drivers on the right side, and NO connectivity to the left side.

Repeat for the engineer's side. 

Now also test for any conductivity between the 2 wires, and between either of these 2 wires and either of the 2 motor leads. There should be no connection, i.e. you have successfully isolated the track pickups from the motor lead.


Now this where we ran into trouble. There was continuity between one of the track pickup leads and BOTH sets of drivers. Pulling the loco apart shows the problem.

You remove the plastic "frame" from the metal motor/gearbox.

Then remove the drivers from the right (engineers) side. Remove 4 screws and split the halves of the motor block.

The picture below shows the 4 pin motor block connector and as it is soldered to the motor itself. On the end of the connector, you see a small brass tab. This tab will contact on half of the motor block, which is the track pickup.


Here is the problem! Look carefully, the outer ends of the board have a little U shaped piece of brass... the outer sides contact the motor block housing, and they are soldered to the outer 2 pins of the connector, so the power coming from the wheels goes to each half of the motor block, and the 2 brass tabs touch the motor block, and then are soldered to the outer 2 pins of the connector. OK, that makes sense.

The 2 inner pins are soldered to the motor leads. BUT WAIT! The picture below shows a blob of solder bridging the motor lead pin to the right side track pickup.

So we had an internal short between one of the motor leads and one of the track pickups. Apparently this is not a rare problem, George Schreyer notes this problem being reported long ago.

So, if you have this problem, you have to correct it.

Once you have corrected it, re-rest that the motor pickup wires in the tender (while connected to the locomotive) are connected to the correct wheels, and no connection to the other side, and NO connection to either of the motor leads.

OK, you have proved the track pickups are right, and isolated from the motor.

Connect the 2 motor leads to the QSI motor plus and minus... do not worry about the polarity right now. You will swap them later if necessary

Connect your track pickup leads to the correct terminals on the QSI, engineers side and fireman's side.

Plug in the QSI and test run it... test it on DCC and if it runs backwards,  swap the motor leads.

Now test on DC, and if it runs backwards from the way you want it, swap the track pickup leads.

You are done with the basic motor and track connections.

Lighting and smoke

Remove the 2 white headlight wires, and extend them to the tender. Connect them to the headlight, and the common/plus/unregulated pin on the QSI. The headlight will dim in reverse, bright in forwards. If it does not work right, reverse these 2 leads. LOOK CAREFULLY, many people do not notice at first that the headlight dims in reverse, and say "it's on all the time"... it is supposed to be this way.

The ashpan light and marker lights will be on whenever there is track power, and the smoke unit will be controlled by the switch. Center is off. Since I don't have it in my hands, I can't tell you which position is on, either up or down.

Here's the finished tender:

Weather Underground PWS KCACARLS78