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Offline danielfb  
#1 Posted : 30 June 2015 13:55:16(UTC)
danielfb

Switzerland   
Joined: 30/06/2015(UTC)
Posts: 4
Location: Zurich, Zurich
Dear all,
This is my first post in the forum. I hope the first of many.

It’s recently since I have started with train modeling. As where I live you can get plenty of analog Marklin second hand for a reasonable price I decided to go for this standard.

Some days ago I got a Marklin 3050 A 6/6 with a faulty direction unit. “An easy thing to fix I though”. I have spent a couple of nights fighting with it and I still couldn’t find the cause. The problem is when I try to reverse the direction. I turn the voltage knob anti-clockwise and the solenoid inside the direction unit attracts this plate or flap that makes the switch changed from one contact to another, fine, but when I turn the knob back to 0 this flap remains stuck to the solenoid and the switch stays in middle way. Sometimes, when I turn later on the knob clockwise to give some voltage, this flap is released from the solenoid and the direction switch makes the right contact so the locomotive starts moving, but sometimes it doesn’t. It’s like if the solenoid is still attracting the flap. I have obviously tried to replace the spring with a new one (twice), without any luck. At first I was thinking that there could be a bad contact that was still ‘feeding’ the solenoid, but there’s only one transformer for my tests and even I lift the locomotive from the tracks the flap remains attached to the solenoid. I tried soldering again all the wires to the direction unit but same again. Funny thing is that if I push the level with my finger, the whole mechanism works fine, the spring seems to do its job. More information I can give is that this flap is black, not cupper like in some other direction units. I has some scratches in the part that makes contact with the extreme side of the solenoid but I don’t think it’s a problem.

What else do you think I could check before I replace the whole unit?

Any help is welcomed!

Thanks,
Danny.
Offline PMPeter  
#2 Posted : 30 June 2015 15:57:02(UTC)
PMPeter

Canada   
Joined: 04/04/2013(UTC)
Posts: 1,272
Location: Port Moody, BC
Welcome to the forum.

I have had a similar issue with uncoupler tracks where there is enough residual magnetism after power is removed from the solenoid that the flapper stays attracted. I solved the problem by attaching a piece of paper to the flapper. That gave enough of a space to break the magnetism when the solenoid was not activated. I'm not sure if you can try something similar on the reversing unit.

Cheers
Peter
thanks 1 user liked this useful post by PMPeter
Offline danielfb  
#3 Posted : 30 June 2015 16:10:18(UTC)
danielfb

Switzerland   
Joined: 30/06/2015(UTC)
Posts: 4
Location: Zurich, Zurich
Hi Peter,

That's a good idea, indeed. I'll try tonight and tell the results.

Thanks,
Danny.
Offline danielfb  
#4 Posted : 30 June 2015 22:51:49(UTC)
danielfb

Switzerland   
Joined: 30/06/2015(UTC)
Posts: 4
Location: Zurich, Zurich
Et voila, it works! Ugly but effective. I wonder how to get rid of this residual magnetism...
Offline Webmaster  
#5 Posted : 30 June 2015 22:58:21(UTC)
Webmaster


Joined: 25/07/2001(UTC)
Posts: 11,161
In the 70-80's we had these tape recorder head demagnetizers, haven't seen a similar unit for many years but they should still exist... Mellow
Juhan - "Webmaster", at your service...
He who asks a question is a fool for five minutes. He who does not ask a question remains a fool forever. [Old Chinese Proverb]
Offline mike c  
#6 Posted : 30 June 2015 22:58:46(UTC)
mike c

Canada   
Joined: 28/11/2007(UTC)
Posts: 7,865
Location: Montreal, QC
If you decide to replace the unit, you may want to consider one of the digital conversion kits, which includes decoder, magnet and the rest of the components that you will need to convert it to a basic Maerklin digital controller. This decoder will work the same as the solenoid reverse unit in analog operation.

Regards

Mike C
Offline danielfb  
#7 Posted : 01 July 2015 08:15:35(UTC)
danielfb

Switzerland   
Joined: 30/06/2015(UTC)
Posts: 4
Location: Zurich, Zurich
Originally Posted by: Webmaster Go to Quoted Post
In the 70-80's we had these tape recorder head demagnetizers, haven't seen a similar unit for many years but they should still exist... Mellow


You won't believe it. I had one of those in my hands a couple of months ago while cleaning up my dad's house.
Offline cookee_nz  
#8 Posted : 02 July 2015 10:24:02(UTC)
cookee_nz

New Zealand   
Joined: 31/12/2010(UTC)
Posts: 3,946
Location: Paremata, Wellington
Originally Posted by: danielfb Go to Quoted Post
Et voila, it works! Ugly but effective. I wonder how to get rid of this residual magnetism...


Basically you'd have to demagnetise the core, generally by passing a much more powerful magnet past it. I've never had one bad enough that I needed to do this (and you risk making it worse) but back in my days of servicing IBM typewriters there was one particular machine that had this characteristic and it was known about from the design stage so a small consumable part was available which was simply a small very thin strip of adhesive copper foil which was placed across the top of the core, worked a treat and might get only get replaced every couple of years.

What I might suggest for yours which may be a little neater is to get a normal sticky label of the type you get on a sheet or a roll, trim to roughly the dimensions you need but a little wider, peel off the wax backing, slip it between the armature and core and press against the back of the armature, then trim the excess with a blade, scalpel etc. I hope you can visualize what I'm describing.

I would have suggested a thin strip of tin-foil curled over the edges of the armature but you really need something that would not itself become magnetized and I think tin-foil might be self-defeating.

Hope this helps

Steve
Cookee
Wellington
NZ image
Offline kiwiAlan  
#9 Posted : 02 July 2015 17:29:31(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 8,067
Location: ENGLAND, Didcot
Originally Posted by: cookee_nz Go to Quoted Post
Originally Posted by: danielfb Go to Quoted Post
Et voila, it works! Ugly but effective. I wonder how to get rid of this residual magnetism...


Basically you'd have to demagnetise the core, generally by passing a much more powerful magnet past it. I've never had one bad enough that I needed to do this (and you risk making it worse) but back in my days of servicing IBM typewriters there was one particular machine that had this characteristic and it was known about from the design stage so a small consumable part was available which was simply a small very thin strip of adhesive copper foil which was placed across the top of the core, worked a treat and might get only get replaced every couple of years.

What I might suggest for yours which may be a little neater is to get a normal sticky label of the type you get on a sheet or a roll, trim to roughly the dimensions you need but a little wider, peel off the wax backing, slip it between the armature and core and press against the back of the armature, then trim the excess with a blade, scalpel etc. I hope you can visualize what I'm describing.

I would have suggested a thin strip of tin-foil curled over the edges of the armature but you really need something that would not itself become magnetized and I think tin-foil might be self-defeating.

Hope this helps

Steve


So called 'tin foil' will be OK as it is actually aluminium (cooking foil). Aluminium is not magnetic unless you get it real cold, and i am not sure even then.

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