TROUBLESHOOTING 8-7:  Head Light Doesn't Always Work.

If this is your first locomotive and your head light doesn't work or it does some of the time, don't panic.  Your decoder probably has directional lighting and your locomotive may be set for reverse.

RECOMMENDATION 8-8:  ALWAYS Ensure That Neither Motor Lead is Grounded to Your Locomotive's Frame

That's right.  Don't trust me.  If I say that the motor in a particular locomotive is not grounded to the frame, don't believe me.  Who knows for sure that the motor that came with your locomotive is the same as the one in mine.  If you have a different motor, your decoder could be destroyed.  So always check that neither motor lead is connected to your locomotive's frame.  Do this by connecting an ohm meter between either motor lead and try every wheel.  Then do the other motor lead and all the wheels.  Note:  The motor frame in all likelyhood is connected to your frame.  This isn't a problem.  It's the leads to the motor, the ones you will soon attach decoder wires to, that are your concern.

Get Yourself an Ohmmeter for Installing Decoders

It is almost impossible to install a decoder into a locomotive without an ohmmeter. An ohmmeter is usually incorporated into a device frequently called a multimeter or digital volt meter (DVM). An analog multimeter (p/n 22-218) – one with a needle – is available from Radio Shack for $15.99. A DVM (p/n 22-810) is just $19.99. If you can afford a decoder for your locomotive, you can afford one of these meters. Let me put it another way, if you can afford to not have one of these and then "let the smoke out" of a decoder, you can afford one of these meters.

Once your purchase the meter, use the lowest ohms setting to determine if your motor is isolated from your frame and from your pick-up wheels. Also use the ohmmeter to trace out the wires – to figure out which is which and where it goes. Finally, use it to figure out which wheels are being used for power pick-up. Like I said, it’s hard to install a decoder in a locomotive without one of these meters.

For more on using one of these meters, read the section on “General Decoder Installation Instructions.”

General Decoder Installation Instructions

It is difficult for this website to help you with your locomotive decoder installations. This is because I don’t have your locomotive. It is not in front of me and I don’t know what is in it or how it was put together. Fortunately, decoder installation really isn’t hard. On this website you will find installation instructions for numerous locomotives. If you don’t see your locomotive listed, these step-by-step instructions below should get you through the project.

Before you start.

If you have an analog ohm meter, you must “zero” the meter each time you use it and after you change ranges. This is done simply by shorting the probes together and rotating the adjustment dial until the meter reads zero. Note that the ohms scale starts on the right side of the meter.

You don’t have to zero a digital meter. However, you will find that a digital meter never reads zero. Typically it will read 0.4 to 0.6 ohms. This is normal. There is nothing wrong with the meter.

These are general decoder installation instructions intended for older locomotives that have no electronic components inside of them or somewhat newer locomotives that may have a few electronic components in them, but do not have an 8-pin connector in them for a DCC decoder and probably were not intended to be DCC ready or were made prior to DCC.

There are three phases to installing a decoder in a locomotive.

I. Figure out how the locomotive was wired.
II. Disconnect everything in the locomotive.
III. Wire in the decoder.

I. Figuring out the locomotive’s existing wiring.

Locomotives that have no electronic components are all wired the same way. The headlight is wired in parallel with the motor. One side of this parallel combination will probably be connected to the chassis if it is metal. This in turn will be connected to some wheels for power pick-up.

You can confirm this by using your ohm meter. Touch all your wheels, including the tender wheels with one probe of your ohm meter. Attach the other meter lead to one of the leads on your motor. If you do all the wheels without moving the test probe on the motor, you should get two sets of readings. One set of readings will be from the motor lead directly to the wheels. The other set of readings will include the resistance of the lamp and motor. Don’t panic if you can’t tell the readings apart at this stage. If you figure out which wheels you are getting power from, you are doing fine. Note that some locomotives may be using tender wheels, in addition to or instead of, driver wheels to pick up power.

Disconnect at one wire going to the motor. Check with your ohm meter and determine if that wire is going to the “engineer’s side” (right side with loco facing forward) or “fireman’s side” (left side with loco facing forward). Note this for later. If you will have to take the motor out and may rotate it, put a mark on the motor so that you know which terminal the removed wire went to.

II. Disconnect everything in the locomotive.

If the locomotive has any kind of electronics in it (but was not purchased “DCC ready”), you will be removing them. This includes directional lighting, constant lighting, mars lighting, and electrical noise filtering circuits.

If the headlight is connected to the chassis, remove headlight and replace with a grain of wheat bulb (for HO) or a grain of rice bulb (for N) in series with a 680 ohm resistor (Radio Shack p/n 271-1117). Do not connect any headlight wires at this time.

Disconnect both wires going to motor. If only one wire is going to the motor, than the motor is connected to the chassis. Even if you have two wires going to the motor, after disconnecting the wires, use your ohm meter to ensure neither motor terminal is tied to the chassis. Check and see if the chassis also connected to wheel pick-ups. You must isolate the motor from the chassis! Use your ohm meter to ensure that the motor is isolated when you are done. This is important! If you don’t do this, you will likely “let the smoke out” of your decoder. Once you let the smoke out, electronic devices never work again.

With the headlight and motor disconnected, you should now be able to use your ohmmeter to conclusively determine which wheels your locomotive is using for electrical pick-up.

III Installing the decoder.

1. Connect the red decoder wire to the “engineer’s side” (right side with loco facing forward) wheel pick-ups.

2. Connect the black decoder wire to the “fireman’s side” (left side with loco facing forward) wheel pick-ups.

3. Temporarily connect the orange decoder wire to one of the motor leads. If you noted which of the wires that were going to the motor were from the engineer’s side, attach the orange wire to the motor lead that you previously identified as the engineer’s side.

4. Temporarily connect the gray decoder wire to the other motor lead.

5. Very important! Test your locomotive on address #03. It should move smoothly and in the direction set on your throttle. If it does, you can permanently attach the gray and orange wires. If the locomotive goes in the wrong direction, reverse the orange and gray wires before permanently attaching them.

6. Connect the white decoder wire to one wire of your headlight (or to the resistor if you are using a grain of rice bulb).

7. Temporarily connect the blue decoder wire to the other wire of your headlight.

8. Very important! Test your locomotive. Function 0, with the locomotive commanded to go forward, should light the headlight.

9. Connect the yellow decoder wire to your rear headlight. Or connect the yellow wire to a resistor if you are using a grain of rice bulb.

10. Temporarily connect the blue decoder to the rear headlight.

11. Very important! Test your locomotive. Function 0, with the locomotive commanded to go in reverse, should light the rear light.

12. Your decoder may have other wires that control functions. Hook them up to your mars light or whatever as if they were a headlight. Be sure to install a 22 ohm resistor in series with any light to be used as a mars light, flashing, pulsating, or gyrating light. If you are using a grain of rice bulb and a 680 ohm resistor, you do not need to add the 22 ohm resistor.

13. Make all your temporary connections permanent and you are done!

SUGGESTION: Locomotives with Filter Circuits

The following was contributed by Mark Gurries

Many locomotives seem to come with some filtering electronics for the motor. This filter circuit often consists of a ceramic capacitor and one or two stick inductors. It exists because some locomotive manufacture are attempting to reduce the "Radio Wave" interference the motors can create when they run. Think motor noise & static noise you get on the TV or Radio type of thing. They add this filter to reduce the interference to comply with some regulation agency that regulates such things. To be clear, most locomotive manufactures have NO filter circuit at all.

The filter circuit was intended to be used with the engine while operating in DC mode as opposed to DCC. As people have found, DCC decoders were not designed to work with these filters. In many cases it has lead to erratic operation. The recommendation is that for DCC, at a minimum the capacitor should be removed completely (clipped out). Removing the whole filter is required if you use a decoder with BEMF (back EMF, load compensation, or speed compensation).

SUGGESTION: Thermal Wire Stripper for Delicate Decoder Wires

Decoder wires in particular can be delicate. So can wires in your locomotives. Sometimes your wires are very short. When stripping any wire you need to be able to hold onto the wire and pull on it rather forcefully. For delicate and short wires, you can't grip the wire and you might break off the wire. For these cases, you need a thermal wire stripper.

Unfortunately, the reasonably priced thermal wire stripper I posted here many years ago is no longer available. I've seen several on eBay. You don't need anything fancy. Buying the cheapest one is fine.

The one I have is shown above. It is the Teledyne; now DMC. It looks simple, but a new one is now about $585 from Mouser Electronics. It's Mouser part number is 654-TW-1. https://www.Mouser.com. I paid much less for mine many years ago. It might not be cheap, but it still works great.

I also found one that is less expensive at $438 and looks fancier. It is shown above. It is available from Hisco. https://www.hisco.com. The Hisco part number is FT802-03-3021. Note that you will need to buy a blade; available seperately.

INFORMATION 8-9: Where to Get Decoders Installed.

No, I don't install decoders as a service. I have my hands full trying to maintain this page! There are a number of people who will install decoders in your locomotive for a very reasonable fee. They advertise on my home page.

INFORMATION 8-10:  Locked Rotor Stall Current.

One manufacturer defines stall current as the locomotive stopped and the wheels spinning.  Others specify it as wheels being held from spinning.  This means the motor shaft is not rotating.  When a motor shaft is kept from spinning, it is called a locked rotor.  This is the highest current the motor will draw.  This is worse, or more conservative, than the current reading that will be obtained when the locomotive is held in place with the wheels spinning.  Therefore, I will report the locked rotor stall current.  You won't go wrong if you select a decoder based on this.

Suggestion 8-11:  Use Plastic Couplers on Locomotives with Metal Chassis or Bodies.

There are now plastic knuckle couplers by several manufacturers.  McHenry, Intermountain, Accurail, and Kadee.  Kadee's #30 is the same as their #5, but plastic.

The reason is not obvious.  It becomes apparent with cars that have metal couplers.  The chassis of the locomotive may be common to one rail or another.  The coupler trip pin can contact a rail when crossing a rail switch or crossovers.  Brass cabooses with lighting or passenger cars are obvious sources of trouble.

In the case of lighted cars, it is easy to say ensure all your hot chassis rolling stock and locomotives are attached to the same rail.  I don't know that this is an attainable goal.

I have been told you can use the #30 Kadee's on the Proto 2000 FA2.

Just because a locomotive has a metal chassis or body, doesn't mean that it is common to either rail or either motor lead.  Don't leave your motor leads common to your chassis!  Installing any decoder, you know this already.

I'm also told the Spectrum Fairbanks Morris H16-44 or E-8 don't have this hot chassis problem.  I have an E-8 that I plan to put a decoder in so I will have to check this out.  I'll start checking for this as I do decoder installations.

INFORMATION 8-12:  Using a Zimo Decoder.

I use the Zimo MX65 series of decoders for my G-scale locomotives because they have back-emf control (feedback, load compensation, speed stabilization, or whatever a decoder manufacturer wants to call it.)   They can be ordered from The Train Connection.  Unfortunately, it does not have special effects like Mars light, strobes, etc. useful to US modelers.

It also does not have flickering firebox effects.  Fortunately, most G-scale locomotives have this already built in.  Flickering firebox is also built into the Soundtraxx products.

These decoders have a ribbon cable connection.  But the ribbon cable does not come with the decoder.  

You can order the cable you need from Digikey.  The part number is C3AAT-1618M-ND .  It is a multicolored, 18"ribbon cable with tin plated contacts for $3.69.  Cut this cable in half and you will be able to do two Zimo decoders.  Since you will mate this connector one time and leave it alone inside the locomotive, you don't need higher grade connector.  Should you want one anyway, a gold plated  cable is $4.24; part number C3AAG-1618M-ND.

Note:  Ribbon cables will fail if it is flexed a lot, handled often, or if strain is placed on the cable.  Strain is particularly important to a cable that is inside a locomotive.  Be sure there is no strain on the cable.  It will fail eventually — and probably a lot sooner than either of us wants!  For the ultimate ribbon cable with strain relief, Digikey sells a gold plated connector with strain relief for $2.05; part number CSR16G-ND.  This is a single connector only.

The last thing you should know about the Zimo decoders is their non-standard numbering system for functions.  Zimo does not follow NMRA standards.  Their functions are labeled one higher than the corresponding NMRA function.  Example:  NMRA function F3 is Zimo function F4.  This does not affect how you use your locomotive once a Zimo decoder is installed.  It only affects how you wire it up.  If you want the F3 button on your throttle activate a feature in your locomotive, you have to wire it to the Zimo F4 output.

Pin #1 on the ribbon cable is the upper left pin when holding the decoder so the ribbon cable connector is on the right.  How do you know which wire coming out of the ribbon connector is #1?  Stick a small diameter wire into the hole on the connector that corresponds with the upper left pin.  Use an ohm meter or digital multimeter to find continuity (reading 0 ohms) between the wire and one of the wires on the ribbon connector.  Important Note: Do not force a large wire into the connector or you may damage the connector.  Use one that gives you a snug fit only and nothing more.

INFORMATION 8-13:  Locomotives with Connectors.

Some locomotives have this connector wired wrong. So look for a pin 1.

If you are to wire up your own harness, here are the NRMA colors that should be connected to the appropriate pins. Again, watch that pin orientation!

Miniature Connectors

This section is dedicated to miniature connectors useful for interconnecting steam locomotives with its tender or diesel A-B units. If you have a favorite connector, write-me for instructions on sending me your photos and information.

Mini Connectors from Micro-Mark

I recently picked up these connectors from Micro-Mark, http://www.micromark.com. They are two terminals with red and black wires. The connectors are polarized — which means you can only plug them in one way. This enables you to paint everything black and still be able to hook them up correctly. You get 10 male, 10 female, and some heat shrink tubing for $12.95. Part number is 83858.

Mini Micro Connectors from Soundtraxx

These are about the smallest connectors I have run across. They are just a pin and a socket. To make the socket the smallest it can be, you solder the wire to the side of the socket cup. Unfortunately, I've misplaced my unused connectors and can't take a photo for you. Check back some other day for when I find them. These connectors are available from Soundtraxx dealers. The part number is 810058 and lists for $9.00 for a pack of 10 pairs of connectors.

Soundtraxx also sells a 2-pin micro connector for $3.50. Its part number is 810012 . I have never used these so I can't tell you any more about them.

JST Connectors from Advantage Hobby

These female and male connectors are available from Advantage Hobby.com . The female connector part number is EFLA243 and sells for $2.99. The male connector part number is EFLA242 and also sells for $2.99.

NMRA Connectors from Litchfield Station

Litchfield Station sells the 6-pin NMRA plugs, the 8-pin NMRA plugs and sockets, and 8-pin sockets with leads. Visit http://www.litchfieldstation.com/xcart/home.php?cat=174 to see all that they offer and pricing.

Socket Strips

I have saved perhaps the best for last. These were designed to be a universal socket for integrated circuits spaced on .1" centers. Because they can be stacked, they are useful in joining locomotives. They are inexpensive and available from most electronic suppliers, such as Jameco Electronics, http://www.jameco.com , p/n 212898 and Digi-Key, http://www.digikey.com , p/n A208-ND.

You can cut these connectors apart and make them any configuration you want. Since they can be stacked, you can use one as a socket and one as a plug. You can also remove the pins from the black molded strips. Care needs to be exercised when soldering to them as the plastic is easily melted.

Contributed by Jim Banner

Jim Banner, of the Saskatoon Railroad Modelers, shows the versatility of these socket strips. Jim can be reached at sask.rail@shaw.ca or visit his group's site at http://members.shaw.ca/sask.rail.

	Break-off integrated circuit sockets are easily converted into small plugs and sockets useful in model railroad work.  These hermaphroditic**  plug/socket contacts come in strips and are available from electronics suppliers.  For example, Digi-Key part number A208-ND is a 25 pin strip manufactured by Aries Electronics.  Price is about 10 cents a pin. ** hermaphroditic = having both sexes, male pins and female sockets, in one body.   They last through many insertion/withdrawal cycles, unlike unisex pins which tend to bend out of shape and lose contact fairly easily.
	The pins are 1/10 inch centre-to-centre along the strips with notches in between to allow breaking the strips into shorter strips.  I find it easier to cut them apart with a utility knife.
	Here a two pin strip is sitting on top of a Canadian cent.
	Soldering wires to the pins is easy if you sweat them on.  Sweat soldering involved tinning the pin, tinning the wire, and tinning the iron.  Then it is easy to hold the wire next to the pin with one hand while touching the iron to the wire and the pin to remelt the solder.  It helps if you hold the strip in place, in this case using a haemostat.
	In most cases, you will want to insulate the solder joints with short pieces of heat shrink tubing.  I use a disposable butane cigarette lighter for shrinking, waving the lighter back and forth under the shrink tubing.
	In some cases, you may want to add a  piece of larger diameter shrink tubing over the socket and the already applied tubing.  This extra tubing helps stabilize the wires, keeping them from breaking off.
	To make a matching plug is as simple as soldering wires into the socket side of a strip.  Sometimes the sockets get hot enough to distort the plastic body of the strip.  My solution is to plug the strip being worked on into a spare piece of strip.  This helps suck the excess heat out of the strip being soldered, and keeps it aligned even if it still over heats.  When tinning the wires, you may find the insulation shrinks back, leaving a lot of wire exposed.  One solution is to strip the wires only 1/32" or so.  Another is to trim the bare section to 1/16" after tinning.  Then reheating the solder in the socket and inserting the tinned end of the wire becomes a snap.
	With two pieces of small diameter and one piece of larger diameter tubing shrunk in place, your plug is ready to use.  The outer tubing is more important with the plug than with the socket as the wires tend to break off right where they are soldered into the sockets.  But if space is a problem, you can eliminate it.
	The plug and socket mated.  When made as above, the thicker parts of the pins are not protected by insulation.  Depending on your application, this may or may not be a problem.  Sometimes these bare sections make testing easier.
	In some applications, bare parts may be a problem.  If so, you can extend the larger diameter shrink tubing to cover the space between the plug and socket.  It does not matter which has the extended tubing, the plug or the socket.  But if you have two sets of identical plugs and sockets, you might want to extend the tubing on the plug in one case and on the socket in the other.  This will help avoid mismating them in the future.
	Separating the plug and socket shown above, we can see the extended outer tubing on the socket.
	To save even more space, you can make single pin plugs and sockets.  All that is required it to cut away the plastic body and work with the pin/sockets alone.  Here two pins are being held in a spare strip while wires are soldered into their socket ends to make two single pin plugs.  For single pin sockets, the spare strip and pin/sockets would be inverted.
	Single pin plugs made this way are narrow enough that they can be inserted side by side into a multi-pin socket.  One of many uses for this arrangement is shown in the photo below.  At top left of this H0 Proto 2000 GP-7 locomotive you can see a two pin socket with both pins connected to the black decoder wire.  Plugged into this are two single pin plugs, each connected to the left side of a truck.  With this arrangement, the power pickups can be easily disconnected from the decoder when it is necessary to remove the weight to lubricate the motor and gear towers.  At top right is a similar socket plus two plugs.  Just below it, four diodes and an LED create a third lighting circuit from a two function decoder, the subject of another article in this series.

	Sockets made this way can be used with more than just plugs.  At far left is a 3 mm white LED plugged into an insulated two pin socket.  At near left is a three lead red/yellow LED plugged into a three pin socket with the wires not yet attached.
	Here a three pin socket is mounted on a piece of 1/16" sheet styrene.  I did not have a ruler marked in tenths of inches handy so I used the socket itself to measure off the 1/10" intervals.  Use a 1/16" drill to drill the holes.
	On the back of the above assembly you can see where the wires were soldered on to the projecting pins, as usual, using sweat soldering techniques.  The black line is left over from laying out the holes.  In most applications you will not need to insulate the solder joints.
	In applications where the wires tend to move around you might want to insulate the solder joints if only to make the joints less susceptible to fatigue failure.

Another application, for which I could not find a photograph, involved epoxying two pin sockets into the ceiling of  a wooden large scale building.  Then the room lights, fitted with plugs, were plugged into the ceiling sockets.  The light fixtures themselves were made from plastic beads turned on an engine lathe and lighted with grain-of-wheat bulbs and warm white LEDs.  Doll house applications would be similar.

Contributed by Earl Hacket

Earl Hackett, who can frequently be found on the Wiring For DCC Q&A Forum, continues to show the versatility of these connectors as he uses the sockets to create a header block where he can plug in a decoder and then plug in the lights, motor, and wheel pick-ups.

Earl interconnects the pins by using circuit boards that have strips of holes in them.

Attached are some photos of a connector made with Jameco PN 212898.  A standard NMRA plug attaches where you see the silver mark on the side.  The circuit board is just cheap stripboard with the traces cut as needed.  In addition to the decoder, this provides connections for two tender trucks, the locomotive drivers (in the case of an articulated, one for each of the engines), and front and rear lights.

The photo of it in the tender also shows the connector pins made from contacts removed from the same connector type.

INFORMATION 8-14:  What decoder is right for my locomotive?

We get that question a lot on the forum. It is rare that we can answer it. New models of decoders and changes in the locomotives make it impossible. We can't keep up with all the features and combinations of decoders and locomotives.

Do this:

Try your local store. If they don't know, contact one of the national mail order places that deal in DCC. They get asked this question all the time. They are the ones that know what decoders are currently available. Maybe someone else has already called on the loco you are interested in.

If they don't know, they will work with you. After all, they want to sell you and everyone else with that locomotive a decoder! I can tell you that some of the decoders and their harnesses that you can buy are because I went through exactly this process! They will ask you some questions about the locomotive. How big is the space? Does it have a DCC connector? How long does the harness need to be? Then they will make up a decoder that fits. Then it appears on their website as a decoder specific for a particular locomotive.

You can certainly try asking on the forum. If that fails, call the people that sell them every day. I don't even bother asking others on my forum. Why? Simple. I need to call and buy a decoder anyway and I want it now — just like you! So call them up, tell them what you want. In a few days, you have a decoder! This is one of those cases where this is simply the best thing to do. Companies that can provide this service advertise on my home page.

Decoder Installation Tips for Specific Locomotives