Adjusting the Lighting on a Eureka Models D50 Class - A Bit of a Re-wire.

Eureka Models D50 Class 5274 pauses at Wollar

Taking a rest in Wollar back platform road

D50 with cab light and crew

The Eureka Models D50 Class NSWGR steam locomotive is very nice and sounds good however the Chinese manufacturer changed the originally specified 8 pin tender to locomotive connection to a 7 pin JST one. This was found when the running engineering sample arrived, so short of costing a lot more to have the chassis dies reworked to fit an 8 pin JST style plug/socket the final production has the 7 pin JST.

Now what this meant was that the headlight and the white front marker lights were then tied together electrically.

I decided that there should be a way to correct this situation and what follows is how I did it.

I will say though that this is no easy exercise and you will need very good soldering skills if you attempt it.

I take no responsibility if you end up with a dead QSI Titan decoder as a result of doing this, you will see why later in the post.

I have to say that the D50 comes apart very easily but is engineered almost too well in that I needed to get a single wire for the white front marker light LED into the locomotive from the tender and there is almost no way in. But, the white 7-pin JST connector sitting in the rear of the die-cast chassis has just enough wriggle room to allow a single fine decoder-size wire to enter the locomotive.

To remove the locomotive body I will refer you to Marcus Ammann's web site where he shows how.

The first step once the body is off the chassis is to remove the smokebox from the boiler to give access to the front lighting. The smoke box is plastic and was made this way to reduce the weight forward of the front driving wheels so that the traction would not be affected. First, the funnel must be removed and this is plugged into the smoke box so just carefully pull it upwards. Note that the plug-in arrangement is rectangular and is offset so note which way yours is as the funnel can go on two ways. One way makes it represent a Beyer Peacock locomotive and the other makes it a North British one, very clever.

Next, carefully pull out the handrail posts from the smokebox, they will remain on the handrail. Once all handrail posts are out lift the handrail at the front enough to clear the headlight, you won't bend the wire as it is springy. With the handrail clearing the headlight slide the smokebox upwards off the boiler then out to the front.



Removing the smokebox

In the smokebox there is a small circuit board for the front lights. This board sits in a slot on each inner side of the smokebox and is held in place with a small amount of glue. The board needs to come out so carefully use a jewellers screwdriver under the board on each side and gently lever the board upwards and it will come away. Slide the board out carefully and note that the headlight LED is wired to the board. There is just enough wire to give access to the board.

Now, as shown in the following photo, cut the trace to the middle resistor marked R4 I guess it was, sorry that I didn't take note. I simply used a scriber to cut through the existing trace which insulates it from the headlight.

Smokebox lighting circuit board - L-shaped trace cut

The wire for the front white marker light will be soldered to the rear of the resistor that was just insulated from the headlight (where the R number is missing). The SMD (Surface Mount Device) resistors on this front board are 102 which is 1K Ohm. But the resistors in the tender are 150 Ohm. I think that this might have happened as 1K Ohm is normally used on a +12v common but this decoder is wired using a +5v common even though a +12v common is available on the decoder. Very odd?

The three large soldered contacts on the left-hand end are for three plungers that contact a small circuit board on the chassis when the smokebox is in place. This is a clever way to get the power to the front lights and allow access but unfortunately, we need to bring the wire for the front white marker lights onto this board. This will be done by adding a small plug and socket into the wire close to the smoke box to allow disassembly later if required. I made the plug and socket from an integrated circuit socket that I got from Jaycar Electronics. This IC socket strip can also be used.

Making plugs and sockets

Use a pair of transistor nippers and clip away the plastic leaving two metal pins. The pin on one fits into the hole on the other one so we just need to solder the wire into the hole on one and the pin on the other then insulate with heat shrink tubing and we have an in-line plug and socket.

Using purple decoder wire cut enough wire to run from the rear of the tender to the front of the loco, it can be trimmed later. Now solder the plug and socket into the wire with about 50mm going to the white front marker light resistor on the small front circuit board, add heat shrink tubing as per the following photo, and solder the short wire to the resistor.

Now the wire needs to be threaded under the motor and gearbox (yes, there is a way through just look carefully at the photos - too hard to explain) and out the rear.

Running the purple wire

The next thing is to unscrew the plastic cover and remove the small rear circuit board to gain access to where the purple wire needs to run under it so that it can exit the loco beside the white 7-pin JST connector.

Rear loco circuit board before rewiring

It was at this point that I decided to add a cab light - just to make it all a bit more complicated. If you don't want to do this then skip the next part.

If a cab light is being fitted then follow the next part.

For the cab light, I needed a blue common wire, so as can be seen, there is a connection on the rear circuit board. I soldered a short piece of blue decoder wire to the contact with the existing blue wire and threaded through the hole as per the photo following.

Rear loco circuit board rewired with a blue common for the cab LED

The rear circuit board can now be screwed back in place making sure that the purple wire exits next to the white 7-pin JST connector.

Rear view of loco - Blue common wire and purple front marker light wire

The cab has a removable floor and cab seat moulding that will just slide out the back of the cab so remove it.

In the cab, I used a 0603 SMD warm white LED that I obtained from ebay with leads already attached.

I glued the LED onto the inner roof in line with the rear of the cab sides. I don't know if this is the correct place or not as I couldn't find any photos showing the placement. I then glued the leads across the underside of the roof to the front corners (one corner each), then down the corner to under the floor. Be very careful not to get glue on the chassis as you don't want to glue the locomotive body to the chassis.

Once the glue has set I very carefully soldered the blue common to the correct LED wire.

Locomotive cab light wiring

I then soldered a purple wire that I had painted white bands on to the other LED wire. I then insulated the solder joints with some 'liquid electrical tape' from Jaycar. Once the insulation had dried I carefully curled the wires and pushed the floor and seat moulding back in place.

The locomotive body can now be reassembled.

The mounting of the smokebox is a reversal of taking it off but getting the handrail posts back into their respective holes can be a challenge as on the driver's side there are five in a row very close together. It can be done but you just have to persevere when four are in and the fifth is difficult and suddenly three come out! Refit your funnel the correct way as mentioned earlier.

Now it is necessary to make up two sets of the plug and socket in-line connections as made earlier for the purple wire at the smokebox. These will go into the purple wire and the purple and white striped wire (for cab light) but inside the tender out of the way. There isn't enough room for them between the locomotive and tender below the running board, I found out the hard way.

OK, that was the easy part, now comes the interesting soldering challenge.

Please study the following photo and note that there are three wires soldered onto the tiny contacts on the QSI Titan decoder circuit board at the rear of the JST connectors, one at the lower left (tender front and two at the middle of the back JST connector.

Extra Titan decoder wiring for the lights

The problem is that the Chinese manufacturer has only wired the JST plugs connecting to the Titan decoder with just the wires needed and because of this there are no metal contacts inside the JST plugs to plug the wires into. The other problem is all the wires are black!

Here is a wiring table I have drawn up that shows both the default QSI Titan decoder connections and the wiring additions and changes that have to be made. You MUST study and understand this wiring diagram.

QSI uses the term Port for the outputs that control lights, etc.

Please note that the QSI Titan decoder has a +5v and a +12v common. The D50 LEDs are using the +5v common not the +12v common normally used.

I initially tried to reprogram the marker lights to change the way they operate, e.g. by default the red rear markers are on when moving forwards with a train, but when trying to reprogram them I found an anomaly with the rear white lights that would be on at times when it shouldn't. It might have been my programming or QSI may have made a non-standard change to the programming. The way I fixed this was to rewire the white rear marker lights to a different lighting output Port.

View of rear circuit board in tender showing White marker light connection - W

The wire for the rear white marker lights connected to the W contact on the small circuit board at the rear of the tender is black as is all the wiring in the locomotive as it comes. This is very confusing but I have seen this previously in other locomotives from a variety of Chinese manufacturers.

This black wire goes to Port 2 which is on Pin 4 on the front JST connector, Pin 1 is at the bottom of the left-hand (front of tender) JST connector in the photo above labeled 'Extra Titan decoder wiring for the lights'. From memory, the black wire goes under the Titan decoder to a resistor and the black wire then goes to the front JST connector to Pin 4. I cut the black wire on the decoder side of the resistor, removed the heat shrink, soldered on a red wire as that is what is the default colour (see wiring diagram), and slipped on some heat shrink to cover the exposed solder joint. This red wire (about to be the wrong colour!) was then soldered very carefully to Pin 8 (this is also Port 8) on the decoder circuit board inboard of the rear JST connector. Now these contacts are only about 0.5mm wide with about a 0.5mm gap to the next contact so you must use a fine point on your soldering iron and solder it quickly, you may need some extra non-corrosive flux to assist as the flux in the core of the fine solder you will use will burn away quickly.

Next is the purple wire for the front white marker lights, Make up the plug and socket, solder into the purple wire inside the tender and insulate with heat shrink (my photo shows the plug below the tender, later moved inside). Now, there is a 1K Ohm resistor in the small smokebox circuit board for the front white marker lights but I put another 150 Ohm into the purple wire (can't remember why now as it isn't really needed). I soldered the resistor directly to the Pin 1 (Port 4) connection at the back of the front JST connector.

The last connection is the purple and white wire for the cab light. Once again make up the in-line plug and socket and insulate with heat shrink. I used a 1K Ohm resistor in this wire to protect the cab light LED. Now, this wire is to be soldered to Pin 7 (this is also Port 7) on the inboard connection of the rear JST connector right next to the previously soldered red wire (see above photo). Here you must be very careful with the soldering, it is very easy to bridge the contacts with solder which must not happen. DO NOT apply any power to the decoder if any contacts are bridged with solder or you could "let the smoke out".

If everything is done correctly you can now put the tender back together.

With all the above wiring and Port changes the decoder has to be re-programmed to make the lights work correctly.

I have a QSI Programmer and I would suggest that you get one (or borrow one from a friend) as they make things a lot easier. The program that works with the programmer is CV Manager which can be downloaded from the QSI Solutions website.

Interestingly, the QSI CV Manager program can be used with an NCE Command Station as there is an option to choose between the QSI programmer and the NCE command station. I am not sure if it would work with an NCE PowerCab though.

Here is my modified Eureka Models D50 file for the CV Manager which you load into the CV Manager program and then write all of the CV tab pages one at a time, it will take a while but it is the safest way.

One advantage of using the QSI programmer is that there are sliders in CV Manager to adjust the brightness of the LEDs and this is useful due to the different resistors used on the locomotive and the tender and to adjust the cab light right down low if you have fitted one. If you use the resistors as I have then this adjustment is already done in the CV Manager D50 file of mine.

Of course, you will need to enter the long address locomotive number when you program that tab page.

If you use JMRI then the Eureka Models D50 is in the latest version but I found that not all the light outputs are available to program just the ones in the D50 as it comes. There are a few more actually available on the decoder as they show in the QSI CV Manager. I used the Rear Cab Light set to Port 8 (CV 115.118.0 set to a value of 8) but it is one of the missing light outputs so doesn't appear in the JMRI Eureka D50 file. I believe that Dave Heap did this D50 JMRI file so perhaps he could add the extra lighting outputs in case someone wants to do some more light outputs.

As there are now two wires running between the locomotive and tender they can't easily be separated (in-line plugs are out of the way in the tender). Using a button die set purchased from Jaycar in 2014, I used a 2mm button die to cut a thread onto the end of the metal drawbar post on the tender for about 1.5mm. I unscrewed the post from the tender prior to cutting the thread. I then screwed on a 2-56 nut (of course a 2mm nut will work) one of several that I have had for many years, this nicely keeps everything together.

Well, this is a complicated rewire so, good luck if you decide to take this on.

Eureka Models D50 5163 drifting downgrade towards Cox's Gap