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Offline PMPeter  
#1 Posted : 13 September 2014 22:15:14(UTC)
PMPeter

Canada   
Joined: 04/04/2013(UTC)
Posts: 1,272
Location: Port Moody, BC
I recently bought 6 brand new K track uncoupler sections 2297 from a European dealer. Five work perfectly through a K83 decoder and one remains in the up position after activation.

Since it is just as expensive to mail it back to Europe under Warranty as buying a new one I decided to open it up to see if there is an easy fix. As suspected the activation bar remains attracted to the electromagnets after activation and stays in that position until pushed down manually.

Is there any known fix for that?

I read in a 2007 thread that this could occur in digital mode since the electromagnets can contain enough residual magnetism in DC to keep the bar attracted. However, this doesn't explain why one out of six behaves like this. It also doesn't appear to be a major problem since I haven't seen too many threads on this compared to the failing turnout actuators.

Cheers
Peter
Offline H0  
#2 Posted : 13 September 2014 22:43:04(UTC)
H0


Joined: 16/02/2004(UTC)
Posts: 15,249
Location: DE-NW
Is it really magnetism that keeps it up or is it a mechanical issue?
Does it go down when a loco drives over it?

Does it still uncouple cars after power was turned off? If yes, then the uncoupler track will be of limited use. Or does it go down at the slightest touch, even from a coupler?

AFAIK operating it with pure AC should remove the magnetism. Do you have a 16 V transformer you can use for a test?
Regards
Tom
---
"In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS
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thanks 1 user liked this useful post by H0
Offline kiwiAlan  
#3 Posted : 13 September 2014 22:59:08(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 8,067
Location: ENGLAND, Didcot
Originally Posted by: PMPeter Go to Quoted Post
I recently bought 6 brand new K track uncoupler sections 2297 from a European dealer. Five work perfectly through a K83 decoder and one remains in the up position after activation.

Since it is just as expensive to mail it back to Europe under Warranty as buying a new one I decided to open it up to see if there is an easy fix. As suspected the activation bar remains attracted to the electromagnets after activation and stays in that position until pushed down manually.

Is there any known fix for that?

I read in a 2007 thread that this could occur in digital mode since the electromagnets can contain enough residual magnetism in DC to keep the bar attracted. However, this doesn't explain why one out of six behaves like this. It also doesn't appear to be a major problem since I haven't seen too many threads on this compared to the failing turnout actuators.

Cheers
Peter


One problem that occurs with magnetic items like this is that the moving armature sticks to the pole piece if there is no enforced gap in the magnetic 'circuit'. It doesn't need much of a gap, a non-ferrous shim of some sort such as a piece of tissue paper or brass shim over the pole piece is probably sufficient.
thanks 1 user liked this useful post by kiwiAlan
Offline PMPeter  
#4 Posted : 14 September 2014 03:46:05(UTC)
PMPeter

Canada   
Joined: 04/04/2013(UTC)
Posts: 1,272
Location: Port Moody, BC
I disconnected it from the K83 and pulsed AC from the lighting circuit into it and it worked perfectly. Tried digital again and it still didn't work properly. So I tried AC several times and it worked fine. Now back on digital and it works. Not sure for how long, so I replaced it with a spare.

A loco did push it down, but I never tried seeing if a coupler would push it down. You could tell it was residual magnetism since the bar was firmly up against the pole pieces and didn't separate unless pushed.

Thanks
Peter
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