I ran Marklin for many years and have spent considerable time looking in to running DC locos on Marklin track. I gave up on the idea. The factor that was the deal killer for me, is that Marklin uses the NEM standard for wheel spacing. This won't cause too many problems with rolling stock if you replace wheel sets, but it does cause problems with locomotive driver sets. The width will have to be slightly altered (narrower). This problem crops up when running through switches and is enough to cause derailments.
I recommend keeping the systems seperate. My Marklin gear always ran great and was very reliable. I eventually sold it and switched to two rail DC so that I could model American prototype.
Guy
see stuff at: the Willoughby Line Site
Changing the trucks will not solve the problem, you need to change the wheel sets to one that are insulated as stated above. I know this because my layout is Maerklin AC. Technically you can run DC locomotives on Maerklin Track if you solder feeder wires from your DC powerpack to the outside rails of the track as long as you run a simple oval, once you add turn outs etc you may have to do some rewireing.
You can buy from Marklin or Trix DC wheel sets, or AC wheel sets, whichever way you want to progress. Usually your dealer provides the very first exchange as long the wheels have not been used for free, but check with your dealer. Either way you get NEM profiled wheels, with the AC wheels being made compatible for old metal based track with metal road bed from the 1960ties, and hence true pizza-cutters.
btw., the term AC and DC here reflects the usage: Marklin center-"rail"/studs compatible wheels are short because the track is short, too, and traditionally this arrangement |:| is fed by Marklin transformers, and they provide AC.
However, a lot of DC stuff can be made to run on Marklin AC |:| stuff by adding a slider and shortening the wheels, and when using more modern AC track (stay away from the metal track).
Best is if you use Marklin "C track" because it has so far the best track capabilties and require the least amount of fiddling on your so far DC stuff. However to make it run, all DC stuff needs to be converted to "AC" mode.
If you feed the whole digitally, then there is not a lot to change either (protocol may be an issue, as AC stuff is rarely fed by DCC), but when using analog, you have to add direction-changer-device to your DC locomotives, as direction changes in analog mode occurs via a over-voltage pulse, and the basic feed is AC anyway. These direction-changers contain rectifiers so you can feed DC motors with them. Without them, you will burn out the DC motors, they do normally not like the AC.
The Marklin AC three rail system uses 'studs' between the rails for power pickup, and returns the power via the two outside rails. I can understand getting 'shorts', as i suspect that both wheels on the axle may not be insulated from one another. Replacing trucks was the fix here.
Your DC locomotives pick up on the right rail and return th power on the left rail. Rewiring them so that all the wheels are in the 'return' curcuit, and adding the 'shoe' that slides down the studs for power pick up, and maybe changing out the DC motor for an AC one - that is too much work!
Keep the the train seperated!
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
I am trying to run marklin rolling stock on a DC track with DC locomotive, and am having all sorts of problems, shorts (changed the trucks), derailings, some of the passenger cars have lights but they do not work. I know that marklin is a three rail system and the cars would normally get thier AC current from the third rail. I am considering going to the three rail system. My question is can I run my DC locomotive on marklin's AC track?