Page 1
Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
http://members.ozemail.com.au/~rossstew/rms/marklin.html 1
Hi All,
The 3748 E70 21 is a good candidate for Telex couplers as the coupling pockets are well supported to
avoid coupler droop. I replaced the original 6090 decoder with a LokPilot 4.0 decoder to get the un-
coupling shuffle/waltz in either forward or reverse using the F1 function key as designed by ESU.
The front and rear lights were upgraded to LED lights using “Rule 17” to dim the lights when the
locomotive is stationary. I also decided to add rear red lights that will change over when there is a
direction change.
If The Telex function is left on when controlling the locomotive manually from a command station the
lights will flash as a warning to remind you to switch off the F1 function.
I decided not to have cabin lights as there aren’t any interior details to light.
This conversion required a lot of planning and experimentation to get the final results shown below.
The photo on the left shows the red tail
lights without any light bleeding to the
centre top light.
The photo on the right shows the head
lights
Warning: - You undertake the following modifications at your own risk. Drilling holes and cutting slots
in the metal casting is required. A high level of soldering skill is required for the wiring of the LEDs.
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Main Chassis Modifications
The locomotive must be stripped down to its component parts making sure hand rails and steps are
removed to avoid damage. Care must be taken not to damage the parts as they are removed.
I spent a lot of time planning how the wires from the Telex couplers and four extra LEDs would be routed
to the decoder area (yellow rectangle) before drilling and cutting any metal.
For the rear there would be a total of 8 wires, main LED x2, extra LEDs x3, Telex x2 and the collector
shoe x1.
For the front there would be a total of 5 wires, main LED x2, extra LEDs x3. The front Telex coupler
wires would be routed under the locomotive to the hole shown by the red arrow.
Holes and Slots
Before drilling and filing I removed the motor.
A 2.5mm hole was drilled at the location of the red arrow and
deburred with a larger drill. At the blue arrow locations I cut a
2.5mm wide slot shown here.
The chassis metal was very hard so some effort to drill and file
was required.
Exit position of the hole from the decoder area.
Rear Front
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Non Drive Bogie Modifications
The orange line indicates where the gears have been ommitted and provides an access point to route the
Telex wires by drilling a 2.5mm hole in the direction of the yellow arrow. I pre shrunk some 3mm heat
shrink tube to fit into the hole to get past the axle position shown by the blue arrow to provide protection
for the Telex wires throught the hole and under the axle.
With the Telex mounted into the coupler pocket I made sure that there was enough flex in the wires to
allow full movement of the Telex coupler and that it would self centre.
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Non Drive Bogie Modifications continued
Note how the Telex wires fit close to the top of the chassis which is above the coupler pocket.
The Telex coupler wires and collector shoe wire exits as shown above. Care should be taken not to
damage the wires while routing them through the slots.
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Drive Bogie Modification
I pre shrunk some 3mm heat shrink tube flat to keep the profile low and glued it in place with hot melt
glue. The wires close to the Telex have a small loop to allow freedom of movement then are threaded
through the tube.
Wiring Diagram Telex and LEDs
The wiring diagram above shows the wiring for the LEDs and Telex couplers. Refer to page 8 for the
connection diagram.
All resistors are 1k 1206 size.
The top LEDs are 3mm warm white.
Marker LEDs are 0603 size
Yellow White
F1 Telex
Rear Front
+Pole
Telex
1k
1k
F2
1k
1k
1k
1k
Top
Marker
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Sub Assemblies
Main Top Lights
For the main top lights I used 3mm warm white LEDs and filed
the shoulder of each LED off to allow insertion into the original
bulb holder.
I soldered a blue wire (90mm) to the anode of the LED and a
black wire (90mm) to the cathode.
Marker Lights Red and White
These LED light assemblies were difficult as there is very little room to mount these in the main chassis.
Using 90mm length wire I soldered the blue wire
across the red and white 0603 LEDs on the anode side
by splitting the strands of the wire to form a tee
section. I wanted the wire to remain centred between
the red and white LED.
For the cathode of the white LED I used a black wire
and the cathode of the red LED I used a grey wire.
It is very important that the wires are centred between the LEDs and no wire
protrudes past the LED extents which would cause shorts with the metal chassis
hole shown by the red rectangle.
The LEDs were tested by using 1k resistors for current limiting before
proceeding to the next step.
To provide a self-centering mount for the LEDs I bent some thin clear plastic as
shown above that were a neat fit in the hole. Before gluing these to the LEDs I
had to tint them.
LED Tinting
The 0603 bright white LED’s I have show a blue tinge to the light
output. To cure this problem I used Tamiya Clear Yellow X-24
acrylic paint.
After the paint had dried I used Gel super glue to glue the clear
plastic mounts to the tops of the LEDs. I also cut some thin black
card, drilled a 1mm hole for the wires as this would be a light baffle
to prevent light bleeding into the top main light.
Once again the LEDs were tested by using 1k resistors for
current limiting.
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Decoder Insulator and Wires
Using thin clear plastic I foldered the shape shown with a slot for the
wires from the rear of the locomotive see brown arrow.
The red arrow shows another
slot and small square cutout to
allow the heat shrink tube to
enter the decoder area.
The decoder is a neat fit seated
in the insulator.
Decoder Wiring Details
I soldered the wires (80mm) required to the correct solder pads as shown in the ESU manual for the
“54614 LokPilot V4.0” decoder. Please note the direction of the wires soldered to the decoder solder
pads.
Description Colour
Motor R Grey
Motor L Orange
Left Track Black
Right Track Red
+ Pole Blue
Head Light White
Rear Light Yellow
Aux 1 Green
Aux 2 Violet Decoder Top View
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Front Telex Wire Connection
The wires for the front Telex needs to be
extended, for this I soldered 90mm lengths of
grey and black wire to a very small piece of Vero
board.
LED Light Limiting Resistor PCB
All resistors are 1k, 1206 size. Under each resistor the copper foil has been cut using a 3mm drill. Please
note the two wire links for the Head Light and the Rear light shown with red dotted lines.
Direct connections from the decoder are F1 Green, F2 Violet, +Pole Blue, Head Light and Rear Light.
Locomotive PCB Original
Direct connections from the decoder are Left Track, Motor R, Motor L and Right Track. The collector
shoe wire is also soldered on this PCB.
F1 Green F2 Violet +Pole Blue Head Light Red Led Rear Light
Top Led Marker Led
Rear
Top Led
Red Led
Marker Led
+Pole Blue
Front
Left Track
Motor R
Motor L Right Track Collector Shoe
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Marker Light Assembly
From the top I inserted the marker light assembly and on the bottom you can see the assembly just below
the surface of the rectangle. I tested all wires to make sure there were no short circuits with the chassis.
In the top view the wires were routed through the cut slot and held in place with a 3mm heat shrink tube
and squeezed into the existing wire channel. I made sure the thin black card was fully seated in the
bottom of the existing light well.
Top Light Assembly
The original light holder is now placed as shown
with the wires routed in the wire channel
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Final Assembly
For the non drive bogie I refitted the wheels making sure that they rotated freely.
With the marker lights fitted and tested I reassembled the bogies to the chassis.
In the decoder recess I inserted a small length of 3mm heat shrink tube through the hole then placed the
decoder insulator over the tube into the recess. Finally I inserted the LokPilot 4.0 decoder into the
insulator.
The front Telex wire extension is shown in position with the wires inserted into the hole and held in
position with a small section of heat shrink tube super glued to the chassis.
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Wiring the Locomotive
The locomotive original PCB is fitted and held in place by two screws. The decoder wires for
Left Track, Motor R, Motor L and Right Track are soldered at this time, see connection diagram on page
8 and colour chart on page 7. The collector shoe wire is also soldered.
Wiring the Lights and Telex Couplers
The LED Light Limiting Resistor PCB should be a snug fit above the original PCB.
Solder the remaining wires shown above and refer to the connection diagram on page 8.
Please note I also placed some tin foil under the top 3mm LEDs to help reflect the light up.
Finally I place thick black card over the PCB to prevent any wires or components being
visible.
Front Telex Wires Front Light Wires
Rear Light Wires,
Rear Telex Wires,
Front White, and Rear Yellow Light Wires,
Collector Shoe Wire
F1, F2 and +Pole Wires
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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CV Values for the LokPilot V4
Warning: Make sure you read the ESU decoder instructions before programming any CV’s
Please note any Value = *xx means the default value wasn’t changed.
The Index settings CV31 and CV32 must be changed when doing direct CV programming.
Motor Settings [Index:0 (CV31=0, CV32=0)]
CV# Name Range Value Default
1 Primary Address 1-255 34 3
2 Start Voltage 1-255 *3 3
3 Acceleration 0-255 20 32
4 Deceleration 0-255 10 24
5 Maximum Speed 0-64 160 255
6 Medium Speed 0-64 55 22
13 Analogue Mode F1-F8 (F0 Lights) 0-255 0 1
51 Load Control Parameter “I slow speed” 0-255 *0 0
52 Load Control Parameter “K slow speed” 0-255 18 32
53 Control Reference Voltage 0-255 100 140
54 Load Control Parameter “K” 0-255 46 48
55 Load Control Parameter “I” 0-255 30 32
66 Forward Trim (1 x Voltage) 0-255 126 128
95 Reverse Trim (1 x Voltage) 0-255 124 128
246 Automatic Uncoupling Speed 0-255 80 0
247 Automatic Uncoupling Move Time (2 sec.) 0-255 60 0
248 Automatic Uncoupling Push Time (1 sec.) 0-255 60 0
Timing Functions [Index:4096 (CV31=16, CV32=0)]
277 Aux1 [1] Turn Off After Timeout (3.28 sec.) 1-255 8 0
285 Aux2 [1] Turn Off After Timeout (3.28 sec.) 1-255 8 0
292 Aux3 Time Delay Turn On/Off (1.64 sec.) 68 0
Mapping Functions to Outputs [Index:4098 (CV31=16, CV32=2)]
362 F1f (forward) mapped to Aux1[1] *4 4
363 F1f (forward) Rear Light[2], Aux1[1] mapped together 32 0
378 F1r (reverse) mapped to Aux2[1] 8 4
379 F1r (reverse) Front Light[2], Aux2[1] mapped together 16 0
394 F2f (forward) mapped to Aux2[1] (deleted) 0 8
410 F2r (reverse) mapped to Aux2[1] (deleted) 0 8
481 F5 Stop, Forward Condition on Aux3 6 4
490 F5f (forward) mapped to Aux3 16 0
497 F5 Stop, Reverse Condition on Aux3 10 8
506 F5r (reverse) mapped to Aux3 16 0
Function Control Settings [Index:4096 (CV31=16, CV32=0)]
Function
Output
Mode Select Brightness 0-31 Special Function
CV# Value CV# Value CV# Value
Head Light[1] 259 2 262 *31 263 132
Rear Light[1] 267 2 270 *31 271 136
Aux1 Telex 275 28 278 15 279 0
Aux2 Telex 283 28 286 15 287 0
Aux3 Cabin Light 291 2 294 6 295 144
Head Light[2] Flash 355 12 358 31 359 128
Rear Light[2] Flash 363 12 366 31 367 128
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Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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CV Values for the LokPilot V4 continued
CV13 has been changed so F1 Telex function won’t turn on but F0 lights will operate when running in
Analogue Mode.
For people that don’t have the LokProgrammer or the ECoS and have to rely on direct CV programming
you may find my article “Using LokProgrammer to Find Undocumented CV’s” really useful.
Please note some CV values may change in time once I have tried running the locomotive in a schedule
with TrainController to test the Uncoupling function. Any changes will be updated once testing is
complete.
Speed profile for TrainController with the maximum speed set at 80km/h
Left is the speed profile
showing all decoder speed
settings.
Bonus Time The bonus file 3748_zip (84Kb) contains the following listed files
3748.yra Icon for ECoS 50200 Icon for ECoS 50000
The file 3748_451.esux can be used as a starting point for a locomotive conversion similar to this loco.
This file overrides any CV values in the table on page 12. It can only be used with LokProgrammer 4.5.1
and above.
Page 14
Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Locomotive Control
Above is the ECoS command station window showing F0 lights on, F1 telex function off, F3 slow mode
off, F4 Inertia on. To the right is the TrainController Train window which has Telex Jog and Telex
Automatic macros.
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Small Problem with F1 Automatic Uncoupling
Using the F1 automatic uncoupling function on the ECoS controller works well for the first time but if
you forget to turn it off once the locomotive has done its uncoupling shuffle, then reverse the locomotive
the uncoupling function will start in the opposite direction which you may not have intended. There isn’t
an option to have a time delay before turning off the function button.
Small Problem with F1 Automatic Uncoupling Solved
Using a Train window in TrainController I have solved this problem by having a list associated with the
locomotive functions that ensures the train has stopped, performs the uncoupling function then turns the
F1 function off.
In the Engine functions window you
will notice the first Coupler “Uncouple
Auto Timer” associated with F1 is
Hidden and the second Coupler
“Uncouple Telex Jog” I have defined
the actions in a List... – On/Off Switch.
It is important that the graphics for the
coupler symbols are different when
triggering the actions from a schedule.
The List of Operations for the loco
is a message followed by a macro
Uncouple Telex(N) Jog
The Uncouple Telex(N) Jog macro
contains a List of Operations Stop
the locomotive, delay 2 seconds,
Play Sound file “train uncoupling”
then the hidden F1 “Uncouple Auto
Timer” is turned “On”, then after a
delay of 4 seconds the “Uncouple
Auto Timer” is turned “Off”.
This works well and is much safer
than operating the locomotive with
the ECoS.
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Tip: Märklin 3748 Electric Locomotive adding LP4.0 Decoder, Telex
Couplers, LED Lights and Telex Warning Light Date: 28-12-2016
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Parts required:-
As always enjoy your model trains.
Part Number Supplier Description Quantity
54614 ESU ESU LokPilot V4.0 Decoder 1
51940 ESU White cable, 0.5mm diameter, AWG36, 10m 1
51942 ESU Black cable, 0.5mm diameter, AWG36, 10m 1
51943 ESU Red cable, 0.5mm diameter, AWG36, 10m 1
51944 ESU Orange cable, 0.5mm diameter, AWG36, 10m 1
51945 ESU Green cable, 0.5mm diameter, AWG36, 10m 1
51946 ESU Grey cable, 0.5mm diameter, AWG36, 10m 1
51947 ESU Yellow cable, 0.5mm diameter, AWG36, 10m 1
51948 ESU Brown cable, 0.5mm diameter, AWG36, 10m 1
51949 ESU Blue cable, 0.5mm diameter, AWG36, 10m 1
E117 993 Märklin Telex Coupler (pkt of 2) 1
207 3877 Element14 1K Ceramic Resistor 0.25W, 1% 6
330PW04C Ledz.com Warm white LED 3mm 2
0603KRCT Ledz.com Red 0603 LED 2
0603LWCT Ledz.com White 0603 LED 2