Running Mrklin trains on DC?

I have some Mrklin gear from when I was a kid that's now approaching the time when it may be appropriate to hand it on to the next
generation. However, I've lost the transformers (I had two, in separate circuits to catenary and rail). As I see it, I have two choices:
1) Shop around for replacement transformers (new or used).
2) Build something myself (the EE in me rather likes that idea). However, regulating AC is a pain and variable transformers of suitable specs are hard to come by. But I could scrounge up a two-circuit DC system from spares at next to no cost. A separate feed for lights and points would be easy (and could quite feasibly be AC if needs be; I can see how some of the solenoids might not work "right" on DC).
So what's the verdict? AC motors should run quite happily on DC (the converse is, of course, not true; running a Fleischmann train on AC will probably fail). But will parts wear faster on DC? Any sparks from poor contact (and I remember seeing them quite often) will be more likely to spot-weld on DC. Experiences, anybody?
/Torsten
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Torsten Lif wrote:

Yes, but they will draw an amazing amount of amps - I had a Marklin V60 diesel which had been converted to DC 2-rail by insulating the weels, and soldering back-ofwheel pickups to the centre rail pickups. It drew 1.5 amps and more. Gave it away.
In your case, I recommend buying a new Marklin transformer. They aren't that expensive, really, especially of you take the effects of inflation into account, and will work just fine with older Marklin equipment.

It will also be very bad for the motor.....

Maybe, but you shouldn't see any sparks. If you do, the rail is rusty or pitted, or grooved from cleaning with an abrasive. Use a contact cleaner/lubricant on the rail and as needed in the motor, and sparking should disappear. Do not use abrasives to clean rail, the scratches attract oily gunk.

How attached are you to these trains? Will they be running with DC trains? If they will be running on their own AC circuit, IMO you should just leave them as AC, and bite the bullet re: purchasing new transformers. If you want them to run on DC 2-rail, you will also have to insulate the wheels, which is no problem with thr rolling stock (just replace with suitable wheel sets), but would a challenge with the engines.
BTW, I wouldn't hand them on, myself. :-) I'd buy the next generation a new train set, running on DC and conforming to international standards, so that if they get bit by the bug they won't be locked into one brand. Trix (made by Marklin) would be a better buy than Fleischmann from this P.O.V, if you decide to go that route.
In any case, you've got a complex decision ahead of you.
HTH&GL
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Wolf Kirchmeir wrote:

Back then, no-one had bothered to enlighten me about the difference between "toy trains" and "model trains". I used them mostly as toys for several years and it was only relatively late that I started building "serious" model landscapes etc. By then, most of it was pretty badly worn; to the point where there now is little chance of any of it ever qualifying as "model" trainsets again.

Sounds just about right (the 1.5 A part, not giving it away :-). My old 15 VA transformer that I got with the starter kit could never quite cope with the power needs of my bigger engine. So I can easily believe they need an amp or two.

Well, they're NOT cheap in the stores around here (Sweden). I'll see what's available used first.

Or simply from a reckless kid (me!) playing with it, throwing the parts in a box when they weren't being used and generally getting them dinged up.

Good advice but quite a bit too late by now.
Any hints on how to get the scratches out...?

No, never.

I was never thinking of converting them. Just of feeding them through the same catenary and/or center rail but with DC instead. Not from any "ideological" reason but for simplicity. I can throw together a 10 A variable-output DC supply from spares in no time and at almost no cost.

I have no intention of modifying anything more than the bare minimum fixing-up to get the stuff rolling. Some parts (couplers, catenary pick-ups etc.) need replacing but they're readily available here.

Ho, hum. I have a sneaking suspicion that the topic of Marklin's AC rail versus 2-rail DC is inflamed enough to get me shunned as a troll on this newsgroup if I start going into detail on it. I know there have been conversion kits for Marklin but I don't recall any detail about them so I can't say how much work would be needed to convert the engines. Rolling stock is simple, of course. But I happen to like the simplicity of Marklin's scheme. I like being able to run a diagonal across the oval without any complicated crossover circuitry. As a matter of fact, if I were to go DC, I'd probably cross-connect the rails and set it up with catenary feed alone. After all, that's more true to the way the originals work anyway. :-)

I'm not buying any new stuff at this point. Junior is far too enthralled by his Gameboy and DS, so my "hope" is that I may be able to divert him by setting up a demo. But I'm not investing in a new set when I don't know if he'll "bite". If he does, I suspect we'll go digital pretty immediately (with any new stuff), but that's for then.

Thanks for your advice.
/Torsten
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Torsten Lif wrote:

I was lucky, I found a copy of Frank Ellisons' Model railroads at the drugstore, a paperback by Fawcett Publications. His Delta Linese were legendary. I reread that book many times, the cover came off, so I eventually made a new cover out of paper-covered card. Still have the book. I wanted a scale layout from a very early age.
I persuaded my brother that the cash we got from friendly relatives should be spent on a Triang train set just before we came over here from England. It consisted of an 0-6-0T "Jinty" and two carriages, which were woefully under scale length. I cut them up and made one scale length car out of them. Still have it, much adapted, with N. American style trucks anew paint job, etc. Looks nothing like an LMS coach now. The Jinty has long since gone to toy train heaven. :-)
[...]>

Well, you might try polishing with a series of ever finer emery cloths. Or look for used track that's better than yours?
Good hunting!
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I have some Mrklin gear from when I was a kid that's now approaching the time when it may be appropriate to hand it on to the next generation. However, I've lost the transformers (I had two, in separate circuits to catenary and rail). As I see it, I have two choices:
1) Shop around for replacement transformers (new or used).
2) Build something myself (the EE in me rather likes that idea). However, regulating AC is a pain and variable transformers of suitable specs are hard to come by.
As an EE, you should have no trouble figuring out how to use a car stereo amplifier to provide nice variable AC, and power/current is well within common junked units ratings.
John H
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I don't think he meant that he was an EE, I think he meant that he found electronics interesting and is intrigued by the idea of doing the task. He may need some input from experienced subscribers to the group
Were's Procter? I bet he uses, or has used Marklin and probably has some ideas. --If we can get them out of him.<g>
The car stereo is a good start. You can also get a variety of autotransformers from Digi-key and other electronics supply houses with varying outputs for nominal expenditure.. Froggy,
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Froggy @ thepond..com wrote:

Actually, I *am* an EE, even though I've been purely in the digital realm for 20 years and almost pure software since ~90.

Yes, I kicked myself a bit when I just saw that one. I even have an old "booster" lying about somewhere that I ripped out of one of my cars ways back because it had too much distortion. Now, feeding 50 Hz off of the stepped-down AC (I'm in Sweden so we're on 240V/50Hz) through a couple of potentiometers and out the amp is trivial (one channel for catenary, one for rail, beautiful). All I need is a "12V" feed to the booster and it doesn't even have to be particularly smooth as the output is going to be rippling at 50 Hz anyways. A transformer, a bridge, some fat caps. I just need to make sure it doesn't ever exceed 13-14 V as that would probably blow the DC-DC step-up converter in the booster. (Thinking out to myself as I type... :-)
It'll run quite hot, but who cares. A winning proposition!

Yeah, well. I was actually toying with some other ideas before connecting up tonight. One was to stick with AC but use a thyristor/triac to pulse-width modulate it, i.e. a simple delay (typically, an RC link) to control how late into the cycle it switches "on". That would be amusingly appropriate if I had one of the engines that came out slightly after mine; Swedish ASEA's "RC" engine, hyped to pioneer the use of thyristors to modulate motor power. But mine is an older ASEA "E" model which used massive banks of resistors. You could smell the heat of scorched dust as they pulled out of a station.
So, I guess, I should just get a "raw" 18 V or so AC and feed it through a set of power resistors (probably have to go wire-wound; 1.5 A!), letting the smell of amps, the "click" of the switches and the surges in speed at each step of the "regulator" add to the authenticity. :-)
If the audio booster burns out, I'll go for the raw AC. A transformer and some resistor-wire. Brutal. True to the original 40's-50's technology of the engine.

/Torsten
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Torsten Lif wrote:

I operated Maerklin until the late 70s. I built my first transistor controller was around 1966 - DC because an AC transistor controller was way beyond my knowledge at that point. I used a pair of diodes, one on each field coil so that the loco could go in either direction! As the only diodes I could source were big and metal cased I had to make a PC board to hold them clear of the chassis and body. I did about a dozen Ma locos over the next few years and the only problem I found was the stator remaining magnetised in the wrong polarity for half a second (aproximately :-)

Ma locos run on 16 volts - well, no modeller needs the top speed they are capable of. Reversing is by the application of 20-24 volts AC but if you use DC the old mechanical reversers will retain magnetism and fail to reconnect the traction current for a time.

I did that back in the early 70s - the motor operation was harsh at lower speeds and 100hz causes the motor to emit a growl.

You will get poor speed response from Ma locos using resistance control!

Not true - Ma has always used variable transformers with the exception of two transistor controllers immediately before they went Digital. (the transistor controllers let the smoke out of the early decoders so Ma dropped the electronic controllers after about a year.

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wrote:

I thionk Torsten meant the technology of the prototype engine! Keith
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Keith wrote:

I thought he was drawing a comparison between prototype and model - oh well, I've been wrong before. :-)
Greg.P.
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Greg Procter wrote:

If you have excess voltage available (1.4 V for a rectifier bridge), you can feed the AC load 50 Hz and still use a single thyristor for the switching.

Like I said, "Authenticity". That's the way the prototype behaved. :-)

I was referring to the technology of the prototype.
But seriously, I'll start by posting "want to buy" ads on some local bboards. Fun as it would be to indulge in a bit of soldering again, time is money and I'll probably be better off investing my time it fixing up the locos and replacing all those crooked couplers.
/Torsten
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Torsten Lif wrote:

If you (pridge) rectify 50Hz AC to pulsed DC you will get 100 pulses per second. AKA 100Hz by my reckoning.

Yes, well, err, - the prototype had and has more mass than an HO model and therefore will not stall so readily nor accelerate as rapidly.

OK.
True - your average older Ma Digital fan will have a cupboard full of Ma transformers that he/she has no use for, coupled with a view that analogue controllers are valuless.

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Greg Procter wrote:

Depending on where you put the load, the bridge and the thyristor, that need not be absolutely true.
I hate ASCII graphics so I won't try to draw a schematic, but if you hook it up so that the AC transformer, the load (trainset) and your controller box are all connected in series, then inside the controller box you simply have the rectifier bridge feeeding the current to the thyristor. In essence, the thyristor sits right across the bridge, "shorting" it, if you will. The load "sees" 50 Hz AC but the thyristor "sees" 100 Hz pulsating DC. I used to make "dimmer" boxes like that for 240 V lamps before they were cheaply available.
Of course, you DO have 100 pulses per second, but half of them are "up" and half of them are "down" so by most ways of reckoning they still form a 50 Hz AC. But I suspect the malformed AC will still cause noise in the loco. It will, almost certainly, emit nasty spikes that may cause noise in any audio electronics in the neighborhood. Especially as it's connected in series with two fairly large inductors (the AC transformer and the loco).
/Torsten
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Torsten Lif wrote:

That's not a circuit I've ever seen! Surely the minimum speed would then be 16v / 2 or 8 volts pulsed DC???

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Greg Procter wrote:

You almost certainly have - many light dimmers for home appliances are wired that way.
It used to be that when we first built thyristor (or triac) -controlled regulator circuits, we'd feed the AC through a rectifier bridge, then hook the load in series with the bridge's output and the thyristor. But that's not the most practical circuit for controlling lamps in your house where the wiring is already in place, so you want a dimmer that can drop into the same form factor hole as your standard switch and hook up to the same wiring.
Simple ASCII graphic (despite my intense dislike for them):
-------- -----o o-----|~ +|------| | | | - AC | | V | | | - | | | /| -------------|~ -|------- --------
The --o o-- points would be where you hook up your load. The feed to the rails in our train scenario. I've drawn the bridge as a block with two "~" inputs and +/- out. The rather tacky totem-pole to the right is the thyristor. I haven't bothered to show any circuitry to feed the gate current but it is simply an RC link, with the resistor (actually a potentiometer) feeding the capacitor from + and the capacitor sitting between the gate and - so that when the capacitor has charged up to the PN-drop voltage of the gate (0.6-0.7 V), current will flow into the gate, the thyristor will switch "on" and remain so until the next zero-crossing.
Remember: This is for feeding AC to an AC load (Mrklin locos on Mrklin rails). If you want DC for feeding 2-rail locos, you end up having to use the DC side and you get 100 Hz and I don't think you'll ever smoothe out the ripples unless you use caps so large you get noticeable delays when changing the voltage setting. But Mrklin locos run best on AC, from what I've learned here on this discussion, so for them it's preferable to use the kind of circuit I've drawn.
/Torsten
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Torsten Lif wrote:

(Duhh) Ok, I've got it now!

They run almost as well on square wave as sine wave - of course "running" and "sound" are two different things!
I played around with different frequencies, voltages and wave shapes at one stage and concluded that the prefered pulse frequency for best slow running is vaguely inversely proportional to the armature diameter. Standard Ma motors worked best around 40-60Hz AC / 80-120Hz DC while N scale motors were best around 200Hz DC. Anything higher than that starts to get irritating on the ear and if you take it out of the human audio range it irritates cats and dogs. Square waves cause more motor noise than sine waves and chopped sine waves are even worse. Worn armature bearings make the whole sound problem worse!
Regards, Greg.P.
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Marklin uses a wound-field motor much the same as Lionel. I have converted many Lionel engines to DC by putting a rectifier in the field such that it becomes energized by DC which always has the same polarity. DC applied to the armature then, will cause it to behave the same as a DC permag motor. switch polarity, and the motor will turn the other way. The rectifier prevents the field from reversing. Froggy,
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Hi Torsten,
Go out and buy a second-hand Maerklin transformer, they are cheap and being of variable transformer design they will give better control than anything you could build for the price.
Regards, Greg.P.
Torsten Lif wrote:

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Torsten Lif wrote:

The field stator iron will magnetise when the loks are operated on DC so you will find there is a noticable delay every time you reverse the Loco.

I don't think any of those is of any real consequence.

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