Solving Common Bad Running Issues With Kato Diesels

Kato makes some fantastic N scale locomotives and they run very well, that is until they don’t.  In this post, I’ll share with you the three most common issues I find as to why these reliable locomotives stop working.

There are of course typical things such as dirty wheels and track, but the three issues I’m sharing with you take a little bit more to fix.  They’re also common on other brands of locomotives that have similar parts.

The first issue has become apparent on this Kato SD40-2, as shown below. This model was custom painted by Paul Begg.  This is a 6-axle locomotive that picks up the power on all 12 wheels.  The power is transferred to the chassis halves via copper strips and then into the circuit board.

With the shell removed you can see the circuit board. This particular locomotive is DCC fitted with a Digitrax DCC drop-in decoder, but I’ve had the same issue with DC versions.

The circuit board or decoder drops into the chassis and pushes forward which clamps it in place and at the same time makes electrical contact with the chassis halves and motor contacts.  Below, you can see the decoder has slid back exposing the electrical contacts at the front.

Close up you can see the electrical contacts, and the slots in the chassis halves they slide into.  Ideally, this should be a tight fit requiring a little force to push the decoder forward.  The friction then prevents the decoder from moving and ensures good electrical contact.  But sometimes the decoder is a loose fit; this may because the DCC decoder is ever-so-slightly thinner than the original circuit board or maybe the chassis has been affected by the pressure of clamping the decoder.  The consequence is the decoder slides in and out easily, and the electrical contact is very poor.

The electrical contacts or pads on the decoder are copper, which is ideal to solder too, so to fix this issue I flash over the pads with a soldering iron to put a thin layer of solder on top.

The layer of solder can’t be too thick, otherwise, it’ll prevent the decoder from fitting at all. To get a thin layer I first use the iron to put some solder on, then I clean the iron tip on a wet sponge and quickly run it over the pad again. Excess solder will be removed on the iron, leaving a thin flat surface.  This may take one or two passes with a clean tip each time.

The decoder can then be pressed in.  It will take a good press as the pads are now thicker, but if it feels like you need to press too hard, rather than risk breaking the decoder, pass a clean iron over the pads again to remove a little more solder.

Once fitted the decoder should not move and you’ll have a solid connection, because the solder is softer than the copper and the chassis will dig into it.

The second issue I see a lot is to do with the actual pickups in the trucks.  The AC4400CWs below, again custom painted by Paul Begg, suffered from this.  The first fix above has already been done. This is one of the older chassis where the chassis screws need to be loosened slightly to release the truck.

With the truck bottom, and side frames unclipped the pickups will fall out.  Each wheelset has a plastic axle and metal wheels with a spike on the outside of the wheel.  The spike fits into the cone of the brass pickup.

The issue is dirt and crud that builds up inside the cup.  Below you can see two pickups from the same truck. I’ve cleaned the cups on the lower one.

To clean these cups I use tiny cotton swabs dipped in Isopropyl alcohol. These fit perfectly into the cups to clean them out.  Another alternative is a small Philips/positive drive screwdriver of a similar size.  One note about using Isopropyl alcohol to clean contacts: if they’re from a 3D printed truck, clean the Isopropyl alcohol off fully before refitting the pickup because 3D printed materials and Isopropyl alcohol don’t mix very well.

As well as cleaning the cups the wheel spike should also be cleaned and for this, I use a regular cotton bud dipped in Isopropyl alcohol.

The last issue is also to do with trucks and is something I’ve come across several times.  Below is another SD40-2.  The decoder is not loose in the chassis and the pickup cups are clean, and as you can see below it’s receiving power as the light is on.

However, if the front truck is lifted off the track the power stops.

Lifting only the rear truck shows the power returns so one or both sides of the rear truck is not working correctly.

This is one of the newer Kato chassis and the trucks simply pull out and clip back in.  When removing the trucks the drive shaft will also fall out, so be extra careful not to lose the bearing on the end of the worm gear as they will also fall off.  Should it fall off note that there is a tiny plastic washer between the bearing and the worm gear.

With the truck removed the problem becomes apparent; you can just about see it in the image above but it’s clearer below. The righthand pickup, with the cups in, has a post that stands up to make contact with the chassis copper strips and it’s bent.

Compared to the one on the other side you can see it’s pointing towards the truck rather than up.  This will prevent making contact with the copper strip and reducing the locomotives pickup by half on that side.  The solution is to bend it back into the right place and this can be done with a pair of tweezers or small needle nose pliers.

Now with the truck reinserted in the chassis, the locomotive should work with either truck on the track.  And with both trucks picking up power, clean pickup cups and a good connection to the decoder, the locomotive should run as well as new.

Clean wheels are also important, and a little lubricant on the gears is also a good idea while you have the trucks out.  If you’re wondering what oils or lubricants to use on the gears I’ve written a post about that which can be found here.

Cutting Out Etched Brass

Etched brass features in several of my model kits and has been used as a way to model tiny detailed parts for many years.  But how do you cut the parts out?

A sheet of etched parts, or fret, normally consists of a sheet of metal with all the parts attached by a half-etched tag.  This means the area around the part has been fully etched away except for a small tag which is only half as thick as the rest of the sheet.  Below is the etched brass ‘Additions’ sheet for my N scale Alco C-855B locomotive.  As well as the larger handrail section there are also several other parts, such as ladders and grab irons, which are much smaller and more delicate.

The half-etched tag serves two purposes; it marks where the part finishes and needs to be cut off, and it makes the actual cutting of it easier, as the material is only half as thick.

With thinner sheets and softer metal such as brass, the tags can be cut with a sharp knife.  I use what is commonly called a Stanley Knife as the blade is strong but sharp.

However, there’s a risk of damaging or bending the parts as the pressure needed to cut the metal is more than the force needed to bend the parts, particularly with tiny parts. Stainless steel etches are harder to cut than brass etches, because the material is harder. This is more noticeable especially on a metal or hard surface, and you may struggle to cut the etch at all. If you cut either material etch on a cutting mat the blade will drag the part down as you exert the force needed to cut through, resulting in bending the part.  The stainless etch below has some very small parts, the squares on the cutting mat are 0.5″ (12.5mm).

This stainless steel etch is from a kit by Keystone Details and zooming in you can see some of the tiny details.  Under the ladder is an electrical box that needs to be cut out and folded to make the box.

If I attempted to cut any of these parts out with a knife they would certainly get damaged.  So I use a special pair of scissors designed for doing this job.  Mine are made by Tamiya specifically for photo-etched parts.

The tips are small and curved which allows them to easily fit in the gap between the part and the fret so you can cut the tab releasing the part.

It’s not always possible to cut the tab off exactly where the part starts, so this little burr will need to be filed off.  Be sure to hold the part firmly between flat surfaces otherwise the filing action could also bend it.

Sometimes the fret is made from fairly thick metal.  The HO DT6-6-2000 etched brass Additions are made from 0.5mm thick brass compared to the N scale ones at only 0.25mm.  This was done to give the desired size of the handrail on the HO model, but it does mean the tabs are much harder to cut.

I use a much larger pair of scissors here with a strengthened set of blades for thicker metal.  These are ideal for removing sections of the fret to enable better access to the parts.

So I use a mixture of the Stanley Knife and scissors, depending on the part I’m removing.  It’s best to test cut a section of the fret that you don’t need, to gauge which tool is best.

This isn’t the only method for cutting parts from etched frets, there are also other tools for cutting photo-etch, however, I haven’t tried them yet because what I have works well for me. As modelers, we’re inventive in our use of tools and materials, but it’s helpful when we find a tool designed to get the job done, ie cut out parts that aren’t bent or burred.

Checking for Shorts when DCC Fitting A Wrenn Locomotive

The Wrenn Locomotives, despite being much older than most things you can get today, are still great locos and normally great performers.  They are not easy to convert to DCC but it can be done and I’ve previously written about the 3D printed sleeves I produce to allow you to do this.  But I sometimes get questions from customers who’ve done the conversions themselves, with my sleeves, and the loco runs very poorly even though it ran well on DC.  In this week’s post, I’ll show you what the most common reason for this is.

Coincidently this week I’ve had two Wrenn locomotives in for DCC fitting so I can use them to point out the issue.  The two locos, as you can see below, are a former LMS Duchess 4-6-2 and GWR Castle 4-6-0.

As well as being very different models visually they are different mechanically as well; the Duchess chassis at the back has a vertical motor and I covered the DCC installation procedure for this here.  The Castle has the horizontal motor and that was covered here.

Before I go any further I should point out one other issue which can cause problems with DCC fitting these locomotives and that is the current draw.  Sometimes older motors, and worn-out motors, can draw lots more current than intended and the DCC decoder can’t handle it.  To find out what the amperage draw is for a locomotive a stall test should be done.  You can read how to do this here.  Both of these locomotives had a stall current of less than 1 amp, so they are ideal for DCC fitting.

So what is the main cause of problems with these?  Starting with the Duchess below you can see I’ve cut off the wires as per the DCC install instructions.  Both motor brushers are still fitted and you can see them touching the collector on the armature.  The left brush holder, which is at the front of the locomotive, is isolated from the chassis, and the right, or rear one, is not.  The problem is often that the left/front brush isn’t totally isolated.  The brush still fits inside a brass sleeve which is wrapped in a rubbery paper-type material to create the isolation.  Over time, remember I said these were old, this material breaks down.  It’s possible heat from excessive running has affected it as well.  The material hasn’t totally disappeared and it’s not a dead short, otherwise the loco wouldn’t run at all, but a very tiny intermittent electrical short happens between the brass sleeve and the chassis.  Running the locomotive on DC doesn’t really affect it too much.  Although it’s not good for the controller, the tiny short will affect the running, but the controller is able to push more amps through the motor to compensate. But under DCC, the decoders are much more sensitive to shorts and are not capable of delivering as many amps.  The result is the locomotive runs very slowly or has no pulling power.

To check to see if this is going to be a problem remove the brush cap, spring, and brush from the left/front sleeve and inspect the insulation.

If it appears to be okay, basically not falling out, an electrical test with a multimeter can be done.  A continuity test, setting the multimeter to the symbol shown below, will check to see if there’s an electrical connection between the meter probes.

With the brush removed and the brush cap replaced, check to see if there’s anything between the two brushes.  This doesn’t work with both of the brushes fitted, as there’s a connection through the motor.  If, when performing the test, the multimeter gives the slightest suggestion that there’s a tiny connection there, it will cause a problem.

The solution for this is to remove the brass sleeve and isolating material and fit a 3D printed sleeve to the left/front as well as to the right/rear.  As the new sleeves are plastic you are guaranteed to have no short.  The customer’s Duchess above is actually in very good condition and is perfect with no sign of a short, so I won’t change the front sleeve, but once the decoder is fitted, if there’s an issue it will be changed.

The Castle with the horizontal motor can suffer from the same thing although it’s not so common. Both motor brush holders are at the back on either side of the motor.  Again I’ve cut the existing wires off but left the heavy gauge wire on the right, which runs from the connecting point to the brass sleeve on the right.  This is because it’s a better connection than relying on the spring to deliver the power.  The right-hand sleeve has the isolating material.

To remove the brush simply pull back the spring and it will slide off and the brush should fall out.

You can then do the same test as shown below.

I originally supplied my Wrenn DCC conversion sleeves in pairs to provide a spare incase something went wrong and one broke, but in hindsight I see it was a good idea as you may need to change both.  The sets I sell are:

Two Wrenn horizontal motor isolating sleeves.

Four Wrenn horizontal motor isolating sleeves.

Two Wrenn Vertical motor isolating sleeves.

Four Wrenn Vertical motor isolating sleeves.

Two Wrenn Vertical & two horizontal motor isolating sleeves.

This vertical motor design was also used in the Hornby Dublo locomotives, 2 and 3 rail, so should you wish to convert any of the locomotives to DCC or repair a DC locomotive which is shorting, the 3D printed sleeves will work.

Using Second Hand Capacitors

This week’s post will be a how-to for a question I get asked a lot.  Can I use second-hand Capacitors?

The reason I often get asked this is modelers often want to use second-hand capacitors to make StayAlive units for their DCC locomotives, and these can be very effective.  But where are they getting second-hand capacitors from?  Most electrical appliances have capacitors in them of one form or another.  A good example of this is an old stereo system I took apart for the motor.  Below you can see the main printed circuit board (PCB) and it has lots of black cylinders which are mostly all capacitors, and ideally sized to fit into small locomotives.

Even the smaller secondary PCBs have capacitors on them.

The main power input board below is a bridge rectifier, the smaller black cylinders are diodes, and it turns AC voltage into DC for the stereo to use, the nice big capacitor is there to smooth out the DC.

These capacitors are all soldered onto the PCB.  With a good soldering iron the capacitor can be removed without damage by heating the two soldered joints, once you have figured out which ones they are, and pulling the capacitor out. 

This capacitor has a working voltage of 24v and a capacity of 1000 microfarads.  The voltage is important because it needs to be higher than the voltage in the DCC locomotive decoder.  This normally does not exceed 16v, so a capacitor like this is ideal. 

But I find the more important question is not whether second had capacitors can be used, its do the work?  Luckily there is a simple test to check this without any expensive equipment.  Some high-end multimeters have the ability to test capacitance but most do not.  Mine does not, but what it can do is test voltage and resistance.

One thing to do before the test is to remove the charge from the capacitor, a full capacitor could damage the multimeter.  This can be done with a metal screwdriver by shorting across the two terminals.  Please note, this is okay for small capacitors in the Microfarad range used in modeling, I would not recommend doing this with large capacity capacitors with capacitance measured in farads!

The two settings I use are both on the left of my multimeter.  Below it is set to 200k ohms and is used for testing resistance.  I will also be rotating the dial clockwise by three positions to 2 which is a DC voltage measurement.

The way this works is first you discharge the capacitor.  Then, with the multimeter set to resistance, connect the probes to the capacitor.  Black negative to the capacitor negative and red positive to capacitor positive.  The capacitor negative is normally clearly marked.  As the multimeter has a battery inside when the probes are connected to the capacitor it will start to draw and store power.  As the stored power increases the resistance will increase so on the display you will see a steady increase in resistance from 0 to infinity.  If there are any big surges or erratic readings, then the capacitor is not working.

The second part of the test is to set the multimeter to volts DC and reconnect the probes.  This will measure the stored voltage and you will see it decease as the capacitor discharges through the multimeter.  Again this should be smooth.

As it happens the capacitor I took out of the stereo was faulty, probably one of the several reasons it didn’t work!

But to show you the principle, I created a short video of me testing a new capacitor.

So the answer to the question “Can I use second-hand Capacitors” is yes, but I would recommend testing them before spending any time wiring them into your locomotives.

If you have a similar question you would like to be answered or explained in more detail, please contact me and maybe I can help.

Adding DCC To Older Locomotives With Smoke Units

Hello all, my apologies for the silence over last month.  It’s been a very busy time and I’ve been doing a lot of work away from home making it hard to work on trains, draw and generally model railroad.  But I’m back and to start with I have a ‘How To’ to share with you regarding adding DCC to an older steam locomotive with a smoke unit.

A perfect example of this is the Hornby Schools Class 4-4-0 as shown below.  This is not to be confused with the new Hornby Schools DCC-ready locomotives which are a very different model.

These earlier models were only designed for analog or DC operation only.  They are tender driven with the tender wheels picking up power from one rail and the locomotive the other.  Adding a DCC decoder is fairly easy but what makes it complicated is the smoke unit.

With the loco shell removed and you can see the smoke unit which has been pulled out of the boiler.  Normally this locomotive only picks up power from one rail, as previously mentioned, but when Hornby added the smoke unit they added a pickup to both rails but this extra pickup only feeds the smoke unit.  This is because, as standard, there’s only one electrical connection to the tender via the drawbar.

In the image above I’ve run four wires through the loco cab into the tender where the DCC decoder and motor are.  Two are from the power pickups bypassing the electrical connection in the drawbar to utilize the extra pickups for the decoder.  The other two are connected to the common DCC wire (blue) and the auxiliary wire (green) and go straight to the smoke unit.

The smoke unit itself is an oil reservoir with a heating element in it.  It runs on 12v DC and sends out smoke when it gets hot.

Normally on DC or analog operation the smoke unit works very well, getting hotter as the locomotive goes faster because of the voltage increases.  But it also draws much more current than a headlight or other features.  So when connected directly to the DCC decoder, as shown above, the amount of smoke is restricted by the current capacity of the decoder.  The particular decoder fitted in this locomotive has a maximum current output of 250mA for its functions, which is not enough to make the smoke unit work.

To solve this some electronics can be added which will allow the smoke unit to draw power directly from the track, but still be turned on and off from the DCC decoder.  To do this I use a bridge rectifier and a relay.

The bridge rectifier, on the left, converts AC power to DC.  The DCC power in the track is basically AC with the DCC signal embedded. This device, which is a set of four diodes, will convert the power to a clean DC power supply that will drive the smoke unit as if it was on full power.  The relay is an electronic switch that can be operated by the DCC decoder and only draws a very small amount of power.  But the switch inside can be used to connect things that draw lots of power, such as the smoke unit.  This particular relay is a Double Pole Double Through (DPDT) switch, which means it can switch two separate wires between two contacts at the same time, but I will simply use it as an on-off switch.  I like it because it’s very small.

The two input connections on the bridge rectifier connect directly to the power pickups in the loco.  The outputs go to the smoke unit with one wire passing through the relay. The symbols on the bridge rectifier are shown below.  The two wavey lines are the AC connections and the positive and negative symbols are the DC.

The relay has 8 pins.  Pins zero and one are the two wires, common(blue) and auxiliary (green) from the decoder which turn the relay on and off. I used pins two and four for the smoke unit.  With the relay off they’re not connected, but when it’s on they are.

I soldered the wires to the components and used heat shrink to cover the bare wires as they could cause an issue if they touched the metal chassis.

Because the parts are small they can both be tucked into the boiler behind the smoke unit, so they’re out of the way when the locomotive shell is refitted.

This fitted DCC decoder has been set up so F1 turns auxiliary on and off.  When the locomotive is sat on a live DCC track pressing F1 will cause the loco to smoke even though it’s stood still.  This could never have been done on DC as the smoke unit needs to heat up and the train would already be moving before that happened.

These parts are readily available from places like Radio Shack, RS components or even some model shops and are an easy way to overcome the issue.   This can also be used when fitting an aftermarket smoke unit such as Seuthe.  I’ve fitted a pair of Seuthe smoke units to a double chimney locomotive using this method with great results.

Next week I plan to have some news on one of my upcoming 3D printed locomotive projects to share with you.

Adding Power Pickups by DCC Concepts

As well as the drawing I do for 3D printing I do a lot of train repairs and DCC installs, particularly sound installs.  These can sometimes be a bit tricky and I often have to use other products to make it work.  Normally I don’t do reviews of products but recently I found something that worked so well I wanted to share it with you.  In this post, I’ll show you what I did to add additional power pickups to a Hornby OO B17 with plastic wheels in the tender.

The B17 has been around for many years and every now and again it gets a facelift as parts are re-tooled and improved.  The most recent version is quite fantastic, but the previous one had, in my opinion, one major problem.  The tender was the same design from many years before, and still had plastic wheels.  The two pictured below are of this version; you can tell by the basic molded coal load in the tender.

This means although the locomotive had been re-tooled to include power pickups on all the drives, it still only had the pickup footprint of an 0-6-0.   For DC operation this is often just fine, but DCC, and in particular DCC sound, the decoder required an unbroken power supply and when you factor in dirty track, dirty wheels, and dirty pickups, the 0-6-0 footprint on this loco simply wasn’t working.

Looking under the tender you can see the plastic wheels and even the hole above the third one which allowed a strip of card with a rough surface to hang down.  A cam on the last wheel used to rub against the surface and make a kind of chuff effect; this dated back to the 80’s and Hornby called it their ‘Realistic Chuff’ effect.

The red you can see through the hole is a stay alive unit.  This locomotive is fitted with a Zimo Sound decoder, but even with the stay alive, if the loco stopped in the wrong place it wouldn’t start again without a push.

The axle for the wheels is simply a bar and the plastic wheels are in two parts.  This design has been repeated on many locomotives of early design.

The first problem is to find metal wheels to use.  The reason why it’s a problem is just about all the current metal wheels come with much shorter axles with pointed ends.  But the old Mainline or Replica Railways (which is now Bachmann) locomotives had metal wheels in their tenders which were the exact same size on long axles.  Of course, this does mean sacrificing another loco but six axles from two tenders is enough to do three Hornby locos as I’ve only replaced two wheelsets in each tender.  An afterthought would be to see if the plastic wheels fit in the Mainline or Replica Railways tenders?

I found two types of wheelsets in the Mainline/Replica Railways tenders.  Some, as with the set on the left, have metal wheels but a plastic axle which doesn’t end in a point.  The center and right side wheelset both have metal wheels and a metal axle, electrically isolated, with pointed ends.

As the original Hornby axle measured  26.35mm I wanted to get as close as I could.  Any longer will cause binding and make it harder to fit the new wheels.

The set with the plastic axle came in just under and worked perfectly without modification.

The set with the metal axle was ever-so-slightly longer, but this was easily remedied by filing off the points on each end of the axles.

As you can see below both types of wheelsets fitted into the tender and they all rotated  very well.

The second issue was how to collect the power from the metal wheels.  Over the years I’ve built many homemade pickup systems, normally from strips of brass that rub on the wheels at some point, but it doesn’t always work well and the pressure of a flat strip rubbing on the wheel creates a lot of drag.

Then I discovered DCC concepts’ gold plated bronze wheel wiper sets.

The pack contains 12 sets of wheel pickups, each picking up from both wheels and a pack of screws for mounting.

The actual pickup is a strip of PC board with two folded brass contacts, both gold plated.  The contacts have a rounded section to provide a pinpoint contact on the wheel which will reduce drag.  Next to the mounting hole are two solder pads, one for each side.

The rear simply has the connection between the pickups and the solder pads.

As you can see below the pickups fit perfectly between the wheels and provide just the right amount of pressure to ensure a great contact with the wheel.

Now it’s time to fit them.  With the tender shell removed you can see the metal weight.  It will be important to keep this as it’ll ensure the wheels keep good contact with the rails, but it’ll need to come off for now.

The weight was held in place with a few spots of glue.

With the new wheels fitted the pickups can be moved around until the ideal location is found.  You need to make sure the rounded part of the pickup is in contact with the middle of the metal wheel flange and not the plastic inner.

Then using a pin vice I drilled a hole, smaller than the screw, in the tender chassis using the hole in the pickup as a guide.  The screw will cut into the soft plastic of the chassis.

The pickups can now be fitted in place.  I also fitted the wheels again at this point to test everthing worked properly.

The screws were longer than the thickness of the plastic chassis and protruded out of the top. That’s why I removed the weight, and they need to be cut and filed down to refit it.

I refitted the weight using some Black Tack, it’s very sticky and malleable, which is ideal for this job.

The solder pad can now be linked with wire.  If you have a large soldering iron you may want to solder the wires on before the pickups are fitted to prevent caching the chassis with the iron as it will melt very quickly.

Lastly, I solder on two wires to connect back to the main locomotive pickup points.  It’s important to ensure you match the tender wheels from the correct side with the loco wheels or it will simply short out.

With the tender reassembled and all the wires connected it was time to test the loco, and it ran very well.  The best test was to raise the loco off the rails, so it isn’t picking up any power and see if the tender pickups worked on their own, which they did, as you can see in the short video below.

I could’ve fitted three sets to the tender, but after testing two proved to be plenty, and both the B17 locomotives from the first picture are now running equally as well as the latest version of this locomotive, which comes with factory fitted tender pickups.

These pickups from DCC Concepts are very good and, I think, very well priced because you get 12 in a pack.  I’ll certainly be using them again. I just hope they bring this product out for N Scale.  You can get the pickups direct from DCC concepts or at a stockist such as Model Railway Solutions in Poole.

Next week I’ll share with you some of the 3D printed parts which arrived last week.