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Marklin 74491 and limit switches
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Offline Thewolf  
#1 Posted : 13 November 2019 18:08:01(UTC)
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Thewolf

Canada   
Joined: 08/09/2015(UTC)
Posts: 2,035
Location: Saint Mathias dur Richelieu-Canada
Hello guysCool

A few years ago the 74491 marklin engines had big problems with their limit switches.

To remedy this, we had to do this:



I know that a long time ago, I know that Marklin released a new generation of engines that should in principle have no problems.

I know all this... except... except... except I don't want to relive such an experience again.
.

My future layout will have 3 levelsc: 2 hidden stations and 1 top.

That's why I'm going to perform this operation on all the motors of the switches of the 2 hidden sations.

I'm assuming:.'''Better to prevent than to cure''.

What do you think of that?

Have a nice day

Thewolf
Project The Richelieu Valley Railway-CS2-Track C- Itrain-Digital
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Offline RayF  
#2 Posted : 13 November 2019 19:45:29(UTC)
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RayF

Gibraltar   
Joined: 14/03/2005(UTC)
Posts: 15,839
Location: Gibraltar, Europe
As long as you ensure that you don't leave the coils energised for longer than a few seconds I think it's an excellent idea. I wish I had done this on my layout....
Ray
Mostly Marklin.Selection of different eras and European railways
Small C track layout, control by MS2, 100+ trains but run 4-5 at a time.
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Offline Thewolf  
#3 Posted : 13 November 2019 20:36:54(UTC)
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Thewolf

Canada   
Joined: 08/09/2015(UTC)
Posts: 2,035
Location: Saint Mathias dur Richelieu-Canada
Originally Posted by: RayF Go to Quoted Post
As long as you ensure that you don't leave the coils energised for longer than a few seconds I think it's an excellent idea. I wish I had done this on my layout....


Thank you RayCool

These parts will only work for a few tens of seconds, there should be no problems

Thewolf
Project The Richelieu Valley Railway-CS2-Track C- Itrain-Digital
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Offline Danlake  
#4 Posted : 14 November 2019 09:01:43(UTC)
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Danlake

New Zealand   
Joined: 03/08/2011(UTC)
Posts: 1,571
Hi Thewolf,

I have done the same with all my switches regardless of version and year it was manufactured.

Best Regards
Lasse
Digital 11m2 layout / C (M&K) tracks / Era IV / CS3 60226 / Train Controller Gold 9 with 4D sound. Mainly Danish and German Locomotives.
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Offline Thewolf  
#5 Posted : 14 November 2019 13:35:18(UTC)
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Thewolf

Canada   
Joined: 08/09/2015(UTC)
Posts: 2,035
Location: Saint Mathias dur Richelieu-Canada
Originally Posted by: Danlake Go to Quoted Post
Hi Thewolf,

I have done the same with all my switches regardless of version and year it was manufactured.

Best Regards
Lasse


Thank you Lasse Cool

For once, I made a good point on the forum LOL LOL

Thewolf
Project The Richelieu Valley Railway-CS2-Track C- Itrain-Digital
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Offline wseltner  
#6 Posted : 17 November 2019 13:51:38(UTC)
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wseltner

Canada   
Joined: 26/02/2012(UTC)
Posts: 12
Location: Kitchner, Onterio
Hello everyone. This issue was caused by a design fault. The original design did not have any capacitors to mitigate the back EMF when these little limit switch contacts opened on end of travel. The result is burnt contacts caused be the electrical arc created on opening. So after a few cycles there is enough of a burn to raise the contact resistance sufficiently to create an open circuit. I repaired all of mine by putting a 0.33 ufd surface mount capacitor across the outside terminal of the micro switch. Just cut out the unused center terminal of the micro switch and the capacitor fits in the space. I also added a 0.1 ufd capacitor across the coils. This required some very thin wire across the coil as there is no room. I also replaced the bad micro switches on mine. I still have all my original switch motors. Have never had a problem since
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thanks 4 users liked this useful post by wseltner
Offline hxmiesa  
#7 Posted : 18 November 2019 11:57:23(UTC)
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hxmiesa

Spain   
Joined: 15/12/2005(UTC)
Posts: 3,520
Location: Spain
Originally Posted by: wseltner Go to Quoted Post
Hello everyone. This issue was caused by a design fault. The original design did not have any capacitors to mitigate the back EMF when these little limit switch contacts opened on end of travel. The result is burnt contacts caused be the electrical arc created on opening. So after a few cycles there is enough of a burn to raise the contact resistance sufficiently to create an open circuit. I repaired all of mine by putting a 0.33 ufd surface mount capacitor across the outside terminal of the micro switch. Just cut out the unused center terminal of the micro switch and the capacitor fits in the space. I also added a 0.1 ufd capacitor across the coils. This required some very thin wire across the coil as there is no room. I also replaced the bad micro switches on mine. I still have all my original switch motors. Have never had a problem since

Excellent!
As the design has changed at least 2 times, do we know if this design fault still exist in hte latest models? (i.e. if capacitors are now installed from the factory)
Best regards
Henrik Hoexbroe ("The Dane In Spain")
http://hoexbroe.tripod.com
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