The Train Doctor


The information on these pages comprises a few (hopefully) helpful hints and maintenance tips gleaned mostly through my own experience. 

There are also some items that have come from various pieces of documentation that the hobbyist should have seen, but may not have, especially where equipment has been purchased second hand and original instructions etc have been lost.

And the inevitable disclaimer: If I'm working on your loco it's my risk.  If you're working on anyone's loco, whether or not you're following my hints, tips, or other advice, and whether or not your Preiserlings are sitting on your shoulder directing your every move, it's all your risk.  








Page 1.  General

Lubrication .............The perils of excess.

Wheels & Tyres ....Be careful you don't "turn a wheel" when changing tyres.

Pick-up Shoes ........Watch the alignment.

Field Coil Leads ....How to avoid breaking them off.

The "light pipes".....Don't glue the lichtkörpers in.

The 7072 control boxes....Boxes "warped" - buttons sticking? A cure perhaps.

Wiring Diagram for a simple analogue loco....not sure where that wire came from? This might help.


Page 2   Digital

Old Transformers ..A warning if you're using these to run digital locomotives.

Analogue/Digital Switching.... Another warning if you're switching back and forth from analogue to digital control

Decoder Leads ......How to stop the wire leads falling off your decoder at installation time.

Address Table for DIP Switch equipped decoders ....If you're DIY-ing

Decoder Wiring Colours  The standard Märklin decoder wire colours and their DCC equivalents

Decoder wiring harness...... Where the wire came from on that decoder. 

Lost MFX Locos...... A work-around for when your MFX loco won't self register.






























Warning: Use of old "blue" Märklin transformers

If you're just converting to digital operation you may be attracted by the fact that Marklin Digital locos can be run in analogue mode, thus enabling several engines to be converted before having to deal with the train control itself.

There is a "gotcha" though, and both Marklin and ESU warn against running digital locos in analogue mode when you're using the old "blue" Märklin transformers.    Apparently at least some models of those old blue transformers are prone to emitting high voltage spikes at the collapse of the 24 volt reversing pulse while others appear to be simply over-voltage at the output, and these high voltage outputs can be sufficient to destroy a modern digital decoder.  The new style (white or grey) transformers have spike suppression and if rated correctly for the input voltage, are OK. 

There's absolutely no problem with using those blue transformers in analogue mode to drive analogue engines, or use them for lighting, signals, points etc. but you shouldn't run your digital engines in analogue mode using such transformers.

The mains input voltages mentioned below relate to the New Zealand scene which is where I'm at, of course.

To check this out I did take some voltage measurements on a few old Marklin transformers chosen at random from some I could easily lay my hands on.  The particular 32VA transformers I have on my layout appear OK and output voltages are as rated (about 16v max "normal" output, and  24v reverse pulse).   Someone brought me an old 280A transformer to look at the other day though, and I measured that as well. It was rated for a 220volt input rather than 230, so one would expect that to inflate output voltage by 5% or so, but this one read up to 19volts on "normal" and the reverse pulse was a whacking 30volts!!  I've also noted that the smaller transformers (16VA and 10VA) tend to be worse than the 30VA ones, and I wondered whether Marklin boosted the output voltage on some of the smaller ones to compensate for voltage drop-off when the load increases, but the old 280A has a 30VA output, and that one I measured certainly had a problem.   

Check the input rating of your transformer (220, 230 or 240 volt)   I certainly wouldn't use a 220 volt rated one if it's going to be anywhere near digital anything.  Check the output voltages as well, but even if all appears ok, bear in mind what Marklin and ESU both say.  One way around the problem might be to put a couple of back to back Zener Diodes across the transformer output to limit the voltage, but I haven't tried playing with this, and it's probably a lot easier just to restrict their use to analogue devices. 

Another Warning: Switching your layout from digital to analogue

And in the same vein as the warning above,  If you're in the process of converting your layout from digital to analogue, you might be tempted to install a switch in the power feed to your layout, so that you can run it in either analogue or digital modes as the mood suits.  Nothing wrong with the idea but there's a couple of "gotchas".

1. Be very very careful with the wiring and switching, and make sure that under no circumstances can you have both power sources (analogue transformer and digital controller) powering the track at any one time.  There's no quicker way to blow up the output stage of your nice new digital controller than by having "foreign voltages" on its output.

2. If you have accessories decoders on your points and signals, you won't be able to feed them directly from the track power as one would normally do.  If you have the power feed for these devices simply "tapped" off the track power, then when you have the layout switched to analogue mode, those accessories decoders will be subject to the analogue 24 volt reversing pulses.  The average accessories decoder won't stand very much of that sort of thing before it turns its toes up and dies.  To protect against this unwelcome situation, one would need to get the power to the accessories decoder from the "source" side of the digital/analogue switch so that the decoders never get to "see" all those nasty analogue voltages.    Make sense?  



















Decoder installation

The ESU lokpilot and related decoders have very thin and not-very-well-soldered-on wire leads.  To save a bit of effort re-soldering wire leads on to decoders (which is pretty fiddly work) the first thing I do whenever I take an ESU decoder out of its packing is run a bead of hot melt glue across the wire leads right up against the decoder PCB, and where the leads come out of the heat shrink.  I've never had a wire fall off since I've been doing that.  Don't use one of those really hot glue guns, and don't use too much.   If you have "lost" a few wires off the decoder though, and don't know where they came from, don't panic: see below under Decoder Harness Wiring.





















Digital Address Table for older decoders equipped with DIP switches



Fitting you own decoders??  The older DIP switch equipped decoders can still be a good choice under the right circumstances, but the chances are that if you're installing a second hand one now, you aren't going to have the instructions about how to set up the address switches.


Note that the table below is good for all Märklin switch-settable decoders. The switches 1, 3, 5 &7 on the standard "8 DIP switch" digital decoders equate to switches 1, 2, 3 & 4 respectively on the 4-switch Delta decoders, and therefore the 15 addresses highlighted in yellow are the only addresses available to the Delta decoders without doing some physical modifications to the decoder itself. 


















































































Wiring colours for Marklin and DCC decoders

The standard Marklin wiring colours for decoders are well known (amongst Marklin enthusiasts) and have been in use for many years now.  With the lack of a viable decoder from Märklin for retro-fitting over recent times though, various "other brand" decoders (ESU etc) became quite popular, but the wiring colour codes on these decoders conform to the DCC standards.  Interestingly, with Märklin finally filling the void in their decoder lineup, they are now using both colour standards on their decoders:  The decoders fitted with a wiring harness conform to the DCC standard; and the 21 PIN decoder "mother boards" have wiring conforming to the traditional Märklin standard.



The table below compares both standards. 



















































































Decoder harness wiring


Have the wires fallen off that decoder and you don't know where they came from?  

Here's where to put them back for some of the more common decoders that I've come across in the course of my repairs & conversions.  You may also need to refer to the decoder wiring colours table above, but note that Märklin themselves don't always follow their own standard colours!

And again, the warning:  The information here is given in good faith and I believe it to be correct, but I can take no responsibility for any damage done if you attempt to follow this information and something goes wrong!

60902 and 611574 Decoders










60922 Decoder







60942 Decoder











60760 Decoder









Typical Delta 66031 Decoder

The early Delta decoders vary markedly and connections may be different depending which "batch" your sample comes from









66032 Delta Decoder







211410 Decoder

Note the non-standard colour coding with this one.  Be careful if you're upgrading to a more modern decoder.





602748 Decoder













602758 Decoder





603648 Decoder









603729 Decoder

Note the purple (negative) common lead to the lamps:  The LEDs in this loco are wired common cathode which makes replacement with a "standard" decoder a bit of a tricky business.









607317 Decoder









684700 Decoder