Improving Power Pickup



There is a small board in most Aristo steam tenders.

The function(s) of this board vary from loco to loco, and more importantly, it is often miswired.

Here are  the functions as much as I can discern:

  1. Provide power pickup from the rails (track power), and feed it to the loco through the first of the two 2-wire cables between the loco and tender.
  2. Connect battery power from a plug on the board to the loco via the 2nd cable between the loco and the tender.
  3. An alternative configuration is to feed the power from the loco to the backup light on certain tenders, which is needed in installations with the Aristo plug in Train Engineer (TE) modules, or the QSI DCC decoder. This is normally the 2nd cable.
  4. A tie point to feed a battery/mu cable out the rear of the tender.

How does the possible miswiring of my tender/loco affect me?

This is an interesting subject, and has ramifications depending on how you are using the locomotive.

If you run DC track power only:

The tender is often wired in such a way that the track/battery switch selects pickup from EITHER the loco drivers OR the tender pickups, BUT NEVER ALL OF THEM. Therefor the loco runs poorly because it does not have all available pickups connected.

Many people have "solved" this by jumpering the "battery" leads to the "motor" leads.

The nice thing about this is that it solves your problem easily. The DANGEROUS thing about this solution, is that if you ever use a decoder that runs from track power, like the plug and play QSI, or any other DCC decoder, you will DESTROY it because you have jumpered the motor to the track pickups, the #1 no no in DCC.

I strongly recommend against this possible solution. Be forwarned. 

My suggestions below avoid this situation, of course.

My suggestion if you want to run DC track power and/or DCC or even battery power:


Another method to solve a miswired situation is to rewire the power from the tender pickups to be in parallel with the locomotive pickups. This is the most logical way to solve the problem. This also leaves the "motor" power wires coming from the locomotive "free" to power a backup light on the tender.

This has a further benefit of ensuring that when using battery power, you NEVER feed voltage from your battery to the rails.

I strongly recommend this course of action.

 If you want to run battery power only: 

I recommend you use the "motor" leads via the small 2 pin socket, and then ensure that no battery power reaches the rails. If it does, you can use a combination of battery/track switch settings and unsoldering the tender pickup wires.  

 To check if your tender board is miswired:

Put the track/battery switch in "track", put the locomotive on track by itself, not connected to the tender. Not if it moves, and what direction.

Now power the loco from the tender only. Put the loco beside the rails, connect the 2 cables between the loco and the tender. If the loco moves when you power the tender, and it moves in the same direction as the loco did by itself, then you are ok.

If not, then the tender board is most likely miswired.

Note that the battery/track switch is sometimes this switch is miswired, or mis-labelled, either on the loco or in the manual. More on this later.


An explanation of "typical" wiring:

Again, there are 2 sets of 2-wire cables going from the tender board to the loco.

One set is the "motor" leads, which connect to the motor. These are also used to power the backup light in some tenders.

The other set is the "battery" leads, which bring the track power from the tender pickups to the locomotive. (This will make sense later) 

Here is just one example of a tender board. This board includes a backup light in the tender (this is a Mallet)  (Up in this picture is towards the loco.)

(I will label the wires with track, batt, spkr, light, mu, pickups)(also find better picture)

  • There are 2 black wires coming down from the top to the upper right side of the board top edge. These wires that bring "rail power" from the tender to the loco. These are the wires that should be active in "track" mode of the "battery/track" switch. Often this is not true.
  • Likewise attached to the upper positions on the board are 2 orange/yellow "polyfuses" which are little self resetting current limiters. Connected to the polyfuses are the leads to the front truck pickups. The right wire is for the right hand rail, and the left wire is for the left hand rail.
  • Following these 2 traces on the circuit board down, there are 2 wires connected to the bottom of the board, these are to the MU plug that comes out by the tender coupler. (note that often these wires are reversed at the factory in the tender and also reversed in the locomotive).
  • There are two more black wires on the top left, in this picture with spots of red and yellow/orange paint. These wires connect to the "motor" wire that goes to the loco, and to the small 2 pin socket immediately below these 2 wires.
  • These 2 connections also connect to the bottom of the board where the thin black and red wires are shown. In this example these 2 thin wires connect to the backup light. One of the 2 leads goes "through" the diode you see on the board, the little black cylinder with the silver band near one end. This makes the backup light come on only in reverse under dc power.
  • The last 2 black wires in the bottom center of the tender board go to the speaker. These 2 leads go "up" to the white 3 pin plug immediately above. Only the 2 outer pins are used in the connector. Note that this design assumes the sound unit is in the tender, since there is no way to get the speaker connections to the loco.


Further understanding the board:

It's evident that while this might have been a clever design originally, it is not implemented in a manner that works for all situations.

Basically, you would prefer to have 3 sets of wires between the loco and the tender:

  1. Track power pickup from the tender to the loco
  2. Battery power to the loco when the batteries are in the tender
  3. "motor" power from the loco to the tender which can drive a backup light.

It's my opinion that the current implementation is often interpreted as "miswired" because Aristo's factory people are trying to combine these 3 functions into 2 sets of wires, combining functions 1 and 2 above. Thus the track/battery switch can NEVER operate properly.

So, once I understood this, I looked at what was the best way to utilize the hardware available. In my case, I need a track power setup, if you are battery only, just follow my recommendation mentioned above.



The main problem to be solved is getting the track power from the tender pickups to the loco correctly. 

Having the track pickups wired to the the large 2 traces on the right hand of the board make sense. Sometimes it becomes confusing which wires are used by the loco for power. No matter how they are wired from the factory, this arrangement makes sense for track power. What I do is wire it the way you see it, and then check that the loco can run from the tender pickups alone.

You will see that the 2 pickup wires from the front truck (one axle each, one to the right rail, one to the left rail) are also connected here, and go throught the polyfuses. So if the tender trucks derail, or get the wrong voltage polarity, you are protected. Keep all modifications this way!

Also notice that any power from the mu connecter by the tender coupler does NOT go through the polyfuses. This is good in that in a mu situation, since if the mu cable went through the polyfuses, they might get too much current from powering another loco, and "trip".

Rewiring for better operation:

Note: this discussion is for TRACK power only.

Test your system:

  1. See if the loco runs without the tender. Set your power supply up so that so it runs forward. Do not connect the tender wires.
  2. Now test it to see if it will run forward with just the tender. Put the loco beside the tracks, and connect the tender wires. See if the loco still runs forwards.

These 2 tests give you a base line for the basic operation of the loco. Now we are going to make sure of the polarity of the wires coming in. You need an ohmmeter to check continuity. It's easier to use one that buzzes if there is continuity (zero ohms), but any meter will do.

If you fail this test, try the same test with the track/battery switch in the other position.

If that fails, you will have to rewire the main board in the loco.

Assuming you have passed the above test, now we will check to see the wiring of the traces on the tender correspond correctly with the right and left rail pickup. 

  1. Take the loco and tender off the track, leave the 2 wires connected between them
  2. Test the continuity between one right hand side driver and the RIGHTMOST large trace. You need to look at the truck and see which one of the right hand wheels has the pickup wire.
  3. Likewise test the continuity between one left hand driver and the LEFTMOST large trace. Again, you need to look at which of the 2 left hand wheels has the pickup wire.

(Refer to the picture of the tender board for the traces, and the following picture of a stock truck)

If your tender was like mine, the right hand trace should connect to the right side drivers and the left hand large trace should connect to the left hand side drivers.

If all is well, then proceed. If not, you can trade things around to work properly, to match how it should be wired. (you might have to reverse the power wires in the tender and/or the loco)

Remove the 2 wires at the bottom right of the board. These are the wires in the cable going out the back of the tender which is used for interconnecting power between locomotives. I want to use this end of the board for better wiring.

Next, remove the right hand thermal breaker from the board. You want to put one lead it in the bottom right hand hole in the board, in the large right hand trace. Let the other lead hang out past the end of the board. This gives a good mechanical connection, since most are just "tack soldered" to the surface of the board, a no-no in electronics assembly practice. If this involves removing the wire from the loco plug, put that wire back in the hole in the circuit board right where the wires and breaker was soldered.

The lead that is "hanging out in space" now should have all tender pickup leads that pick up from the right rail. To faciliate this, I recommend both visual inspection and using the ohmmeter. In a stock setup, this is just one wire. In my modification (below) it is 4 leads. Take the weights off, and see how the wires come up from the trucks, test each one with the ohmeter. Insulate the connection to the thermal breaker with heat shrink, or tape.

Similarly, move the other thermal breaker into the bottom hole for the left hand trace and solder the lead(s) for the left hand wheel pickups to it. Note: if you are going to complete the next phase for improved power pickup, then do NOT solder the 2 truck pickup leads to the polyfuse at this time.

Now there should be just 2 wires in the upper 2 right hand traces, and these lead to the plug to the loco, and they are in the holes in the circuit board.

There should be one breaker each in the 2 holes in the bottom of the board, one in each of the 2 large traces, and the tender pickup wires should be soldered to these breakers.

At this point your locomotive should be able to be powered from the tender only.

This completes the modifications for improved mechanical and electrical connections to the tender board, and completes the prerequisites for the next step.

Increasing the consistency of power pickup:

"Stock" situation:

  1. The Aristo tender only picks up power from 2 wheels.
  2. The power is picked up from eyelets that are under the brass bushings the axles ride in.
  3. These bushings are not a close fit, so with the bouncing around, the consistency of the electrical path between axle and axle bushing is not very good.

Modification plan: 

My modification consists of:

  • Adding 2 more pickup wheels to total 4 pickup wheels (Stock 4 axle tenders only pick up on 2 wheels)
  • Rearranging the "pickup" wheels to simplify the wiring and avoid mistakes
  • and the "new" contribution: adding redundant pickups to each axle

These together resulted in a significant increase in overall power pickup.

Step 1: Remove trucks from the tender.
  • Remove the weights from the tender. They "trap" the wires underneath.
  • Remove the trucks from the tender. If the 2 truck pickup wires are still soldered to the polyfuses, unsolder them.
Step 2: Disassemble the trucks.
  • Keep the parts with each truck with that truck.
  • Turn each truck over, and remove the plastic spring from only one side of the truck. The "leaf spring" comes out and you can take the truck apart and remove the wheelsets.
  • Now is an excellent time to regauge your wheelsets, they WILL be too tight per the Aristo gauge and NMRA specs! Take my advice, do it.

(show pictures here of removal and disassembly)

  • You can now see the 2 eyelets (on the front truck only) that are behind the bushings. Since you are picking up from the axle only, the wire and eyelet only pick up power from the UNINSULATED wheel.

  • Remove the 6 bushings (leave the 2 with eyelets/wires
  • I use a pair of pliers with curved jaws to gently twist the eyelet out
  • Be sure NOT to crush the bearing from too much pressure, be gentle

(show picture of pliers on the bearing to remove it, and removed bearings in background)

Step 3: Assemble 6 more wire and eyelet assemblies

We are going to make 6 more wire/eyelet assemblies, so we pick up power from BOTH ends of every axle. Since we are picking up from the axles only, with 4 axles, all we get is 4 wheels, since only ONE wheel is connected to each axle. This is a point of confusion, because most people will naturally associate 8 wires with 8 wheels, but what we are doing is picking up from EACH axle TWICE. This is to improve the power pickup consistency, due to the small and inconsistent contact "patch" between the end of the axle and the brass bushing/bearing/journal.

Note: how you do this is dependent on your ability with a soldering iron. Notice the nice long "tail" on the stock Aristo "eyelets". It's easy to solder a wire to this eyelet terminal and keep the solder/wire "bump" far away from the axle.

I have used readily available crimp terminals, and have soldered a wire on the very short tab left by cutting the crimp part off. You might have to get "longer" terminals if you are not as handy. My method does address the clearance between this solder "bump" and the insulated wheel, which must NOT touch.

  • Get some ring terminals that are close to the size of the brass bushing. I had to ream the ones I found to make a close fit. I prefer this method since the "flange" on the brass bushing is small, so I want the bushing to just BARELY fit into my eyelet assembly. That ensures a good electrical connection.
  • Ream the holes in the 6 ring terminals out so that a brass bushing JUST fits in. I used a tapered reamer, or you could use a rat tail file, or a sharpening file for a chain saw.
  • Now cut off the "crimp part" leaveing as much metal on your eyelet as possible.
  • Now tack solder a 12" wire to each eyelet as close to the edge as possible. You must not blob solder on the part where the brass bushing flange will sit. Try to find stranded wire about 20-22 gauge. To put it in visual terms, larger that what Aristo used for the 2 existing pickup wires, and slightly smaller than the wires that are in the 3 external cables. 

(show picture of ring terminal after reaming, with bushing test fit, and assembled wire/eyelet set)

Step 4: assemble eyelets and wires into trucks
  •  Press a bushing through each eyelet, leaving your solder connection facing away from the sideframe. Press the bushings all the way in.
  • Inspect each bushing so that you are confident they are completely seated and in straight.

(show picture of assembled trucks)

Step 5: reassemble the trucks
  • In the front truck, put all the uninsulated wheels on the right side.
  • In the rear truck, put all the uninsulated wheels on the left side.
  • Be sure to put a small washer on the axle tip of the INSULATED wheel side. This keeps the "lip" near the axle from touching the eyelet assembly on that side. This would cause a short. I used a metal washer, but nylon would be fine. The idea is to keep the insulated wheel from touching the sideframe/eyelet assembly. Just find something of the right thickness and a close fit on the axle.
  • Reattach the "leaf springs" to hold everything together.
  • Position the eyelets so the wires point towards the center of the truck.


Looking from the top down on the journal:

  1. The black plastic of the journal
  2. The silver is the eyelet with a wire soldered to it. These is a crimp terminal tin plated.
  3. The brass is the original brass axle bushing, pulled out and put through the eyelet and replaced
  4. The bottom silver is the small washer I added so that the projecting "lip" of the insulated wheel cannot touch the eyelet wire. I only add this small washer on the insulated wheel side.

This has the added benefit of reducing the excessive side to side slop in the wheelsets.

Step 6: dress the wires on the top of the trucks
  • From the top, thread the wires as shown, and secure with a dab of glue. This helps keep the wires away from the wheels.

  • Check your work, look for the wheels hitting the wires. You can usually bend the wire slightly as it leaves the eyelet to keep it away.


Be careful not to pinch the wires under the tender weights, notice that you dress the wires flat under the weights 



Step 7: wire the pickups to the polyfuses.

Note: The method presented here is a balance of performance and ease of modification. There may be layout track work quality circumstances that present operational issues that can be mitigated by alternating the wheel / axle orientation within each truck. However, the trade-off of doing so may introduce a wiring complexity that can invite the risk of mistakes.

Thus, the method presented here is to wire each 2 axle truck with both axles in each truck having the same orientation.

  • Thread all 4 wires from each truck up the large hole and measure out to the poly fuse leg.
  • Once cut, strip about 1/2" of each wire
  • Twist each group of 4 wires together and tin the group.
  • You should now have 2 groups of 4 wires, 4 from the front truck and 4 from the rear.
  • Solder the wires from the front truck to the right hand polyfuse.
  • Solder the wires from the rear truck to the left hand polyfuse.

Your assembly should look like this: (please insulate the wires on the polyfuses with some tape!)




Step 8: test.
  • With a voltmeter on continuity or ohms, ensure that there is no short circuit between the 2 large traces on the board.
  • Test that the right hand wheels on the front truck are connected to the right hand trace.
  • Test that the left hand wheels on the rear truck are connected to the left hand trace.
  • If this all checks out, then place the tender on the track, the loco beside, and see if the tender powers the loco in the proper direction.

If you have problems, go back and check your wiring for the pickups, and check for shorts between the front and rear truck, or between an eyelet and an insulated wheel. Also check that all the uninsulated wheels are on the right side on the front truck and the left side on the rear truck.

Other modifications:

For the QSI decoder install, I needed a wire to run from the loco to the tender for the speaker. Since there was no backup light in my mikado tender, and I'm running DCC, I have no need for the "motor" wire.

See the QSI install section for how I changed this. Basically I removed the other pair of wires (the "motor") from the top left of the board and connected them to the connector supplied, and plugged it into the speaker jack

Weather Underground PWS KCACARLS78