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Offline Danlake  
#1 Posted : 01 October 2014 22:36:39(UTC)
Danlake

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

Just completed overhaul of the Marklin 7051 crane I bought on Ebay.

Even though it was brand new everything had seized up...

But working very nicely nowBigGrin

Building my own little control box with momentary push buttons.

However I noticed that the electro magnet stays magnetised after switching it on (even though I switch off the current)?

Any ideas what the problem can be?

Thanks!

Brgds - Lasse
Digital 11m2 layout / C (M&K) tracks / Era IV / CS3 60226 / Train Controller Gold 9 with 4D sound. Mainly Danish and German Locomotives.
Offline Bigdaddynz  
#2 Posted : 02 October 2014 06:03:29(UTC)
Bigdaddynz

New Zealand   
Joined: 17/09/2006(UTC)
Posts: 18,661
Location: New Zealand
Sounds like the contacts in the switch box are not disengaging when you release the push button. The circuit pretty much runs from the switch contact directly to the magnet / magnet light. Also, check that there are no shorts on the contacts underneath the crane cab.
Offline Danlake  
#3 Posted : 02 October 2014 07:26:00(UTC)
Danlake

New Zealand   
Joined: 03/08/2011(UTC)
Posts: 1,571
I tried wiring up manually and when I disconnect the cable the light in cabin goes off but the magnets stays magnetised (i.e. the piece of steel nail will not drop from the magnet)...

Brgds - Lasse
Digital 11m2 layout / C (M&K) tracks / Era IV / CS3 60226 / Train Controller Gold 9 with 4D sound. Mainly Danish and German Locomotives.
Offline jvuye  
#4 Posted : 02 October 2014 11:49:56(UTC)
jvuye

Belgium   
Joined: 01/03/2008(UTC)
Posts: 2,881
Location: South Western France
Originally Posted by: Danlake Go to Quoted Post
Hi all,

Just completed overhaul of the Marklin 7051 crane I bought on Ebay.

Even though it was brand new everything had seized up...

But working very nicely nowBigGrin

Building my own little control box with momentary push buttons.

However I noticed that the electro magnet stays magnetised after switching it on (even though I switch off the current)?

Any ideas what the problem can be?

Thanks!

Brgds - Lasse


Looks like remnent magnetisation could be the culprit.
If you feed the magnet with DC, you will have that problem.
Normally if you feed it with 16V ac (as prescribed) it will be a wee bit noisier, but the problem should dissapear.
Keep us posted!
Jacques Vuye aka Dr.Eisenbahn
Once a vandal, learned to be better and had great success!
thanks 3 users liked this useful post by jvuye
Offline Br502362  
#5 Posted : 02 October 2014 13:31:01(UTC)
Br502362

Finland   
Joined: 05/03/2014(UTC)
Posts: 680
Location: Finland
Originally Posted by: jvuye Go to Quoted Post
Originally Posted by: Danlake Go to Quoted Post
Hi all,

Just completed overhaul of the Marklin 7051 crane I bought on Ebay.

Even though it was brand new everything had seized up...

But working very nicely nowBigGrin

Building my own little control box with momentary push buttons.

However I noticed that the electro magnet stays magnetised after switching it on (even though I switch off the current)?

Any ideas what the problem can be?

Thanks!

Brgds - Lasse


Looks like remnent magnetisation could be the culprit.
If you feed the magnet with DC, you will have that problem.
Normally if you feed it with 16V ac (as prescribed) it will be a wee bit noisier, but the problem should dissapear.
Keep us posted!


I have exactly the same problem with my 7051 crane which is from 60's.
I feed it with 16V AC.

Can't figure out what causes this Confused
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Offline Purellum  
#6 Posted : 02 October 2014 14:12:43(UTC)
Purellum

Denmark   
Joined: 08/11/2005(UTC)
Posts: 3,498
Location: Mullerup, 4200 Slagelse
Cool

Quote:
I have exactly the same problem with my 7051 crane which is from 60's.
I feed it with 16V AC.


Maybe somebody before you used DC for the crane?

Per.

Cool
If you can dream it, you can do it!

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In case this is not legally possible:
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Offline Br502362  
#7 Posted : 02 October 2014 14:18:24(UTC)
Br502362

Finland   
Joined: 05/03/2014(UTC)
Posts: 680
Location: Finland
Originally Posted by: Purellum Go to Quoted Post
Cool

Quote:
I have exactly the same problem with my 7051 crane which is from 60's.
I feed it with 16V AC.


Maybe somebody before you used DC for the crane?

Per.

Cool


Hi Per,

I didn't even think that possibility Laugh
It seems that I am beginning to be old...

Must buy a new one from ebay.de

Thanks

Best regards
Åke
Offline Markus Schild  
#8 Posted : 02 October 2014 17:50:09(UTC)
Markus Schild

Germany   
Joined: 14/01/2006(UTC)
Posts: 1,802
Location: Wurttemberg
Originally Posted by: Br502362 Go to Quoted Post

Must buy a new one from ebay.de



Hi Åke,

No, you don't need to buy a new one. Using the magnet with AC will de-magnetize it in a short time.

Regards

Markus
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Offline kiwiAlan  
#9 Posted : 03 October 2014 00:07:10(UTC)
kiwiAlan

United Kingdom   
Joined: 23/07/2014(UTC)
Posts: 8,082
Location: ENGLAND, Didcot
Originally Posted by: Markus Schild Go to Quoted Post
Originally Posted by: Br502362 Go to Quoted Post

Must buy a new one from ebay.de



Hi Åke,

No, you don't need to buy a new one. Using the magnet with AC will de-magnetize it in a short time.

Regards

Markus


Hook the magnet directly to the track outputs of a Marklin analogue transformer and slowly move the speed control from maximum to minimum. Doing it with a reducing voltage helps to reduce the magnetisation.

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Offline Tom Jessop  
#10 Posted : 03 October 2014 04:04:23(UTC)
Tom Jessop

Australia   
Joined: 14/12/2002(UTC)
Posts: 800
Location: Newcastle NSW Australia


Is the magnet face surface coated with varnish or a piece of plastic ? Most coils need a air space between the object being attracted by magnetism & the face of the coil . All telephone relays had an adjustable brass screw in older exchanges & a plastic shim in the newer exchanges . This prevented most residual magnetism problems & allowed a definite release of the armature when power was removed . Naturally this is on a DC powered supply as AC reverses itself 50 or 60 times per second depending on where you live .

Cheers Tom in Oz
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Offline Br502362  
#11 Posted : 03 October 2014 07:11:26(UTC)
Br502362

Finland   
Joined: 05/03/2014(UTC)
Posts: 680
Location: Finland
Good morning,

Thanks for all hints guys ThumpUp

Must test that de-magnetizing process in the evening and make the plastic spacer too.

Best regards

Åke
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Offline Tom Jessop  
#12 Posted : 03 October 2014 12:09:34(UTC)
Tom Jessop

Australia   
Joined: 14/12/2002(UTC)
Posts: 800
Location: Newcastle NSW Australia


For the last few hours I have been trying to think of the name of the brass screw we used to adjust when doing maintenance in exchanges ,Silly me its called a Residual screw ,doh. The shim only needs to be very thin , about 2 or 3 thousandths of a inch .


Cheers Tom in Oz. with old age creeping up .
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Offline Br502362  
#13 Posted : 07 October 2014 09:31:19(UTC)
Br502362

Finland   
Joined: 05/03/2014(UTC)
Posts: 680
Location: Finland
Yesterday evening I was de-magnetizing cranes magnet.

First with full power (setting 250 on 6647 white transformator) 10 minutes
then 5 minutes with each setting 200->150->100->50

No improvement Confused

Is it possible that wires from magnet are connected to crane wrong way? Or does it matter at all? Or was the de-magnetizing time too short?

Best regards

Åke
Offline Chook  
#14 Posted : 07 October 2014 10:02:29(UTC)
Chook

Australia   
Joined: 15/08/2012(UTC)
Posts: 234
Location: Perth, Western Australia.
HI Ake. I am wondering if your "metal load" is magnetized and not the crane magnet?
Ok here is a quick test. Get yourself a 150mm screwdriver and then get a dressmakers pin.
Place the screwdriver blade next to the pin and see if the pin is attracted to it. If the answer is yes then strike the screwdriver blade several times onto another large metal object. This will demagnetize the screwdriver. Again test the screwdriver with the pin and continue doing this until the screwdriver does not attract the pin.
Now suspend the screwdriver between your fingers and bring it gently towards the crane magnet. If the screw driver is attracted towards your crane magnet then yes the crane magnet is magnetized.

See how you go and report back.


Regards.......Chook.
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Offline Tom Jessop  
#15 Posted : 08 October 2014 22:30:39(UTC)
Tom Jessop

Australia   
Joined: 14/12/2002(UTC)
Posts: 800
Location: Newcastle NSW Australia
Any progress with the laws of magnetism ?

Regards Tom in Oz
Offline Br502362  
#16 Posted : 09 October 2014 07:01:23(UTC)
Br502362

Finland   
Joined: 05/03/2014(UTC)
Posts: 680
Location: Finland
No yet. I have been busy lately but today I will be able to spend some time in the man cave Drool

Regards

Åke
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Offline Danlake  
#17 Posted : 10 October 2014 03:26:28(UTC)
Danlake

New Zealand   
Joined: 03/08/2011(UTC)
Posts: 1,571
After running my crane for a while (with AC supply), the magnet is working fine now.

Thanks for advice on this topic.

Brgds - Lasse
Digital 11m2 layout / C (M&K) tracks / Era IV / CS3 60226 / Train Controller Gold 9 with 4D sound. Mainly Danish and German Locomotives.
thanks 1 user liked this useful post by Danlake
Offline Br502362  
#18 Posted : 10 October 2014 07:04:49(UTC)
Br502362

Finland   
Joined: 05/03/2014(UTC)
Posts: 680
Location: Finland
Hi all,

Tested my crane yesterday evening. I tried the method Chook earlier described and found out
that cranes magnet didn't attract demagnetized screwdriver. But cranes magnet still stays magnetized many minutes
after power is switched off. Cursing

Crane magnet has the original transparent plastic shield in it's place. I solved this problem by
making a second plastic shield which covers the whole under surface and glued it there. Material is ultra thin plastic
which is used to wrap packages in warehouse before shipping.

Now the magnet works perfectly but I still don't know what caused this problem Laugh

Regards

Åke
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Offline Chook  
#19 Posted : 10 October 2014 07:54:48(UTC)
Chook

Australia   
Joined: 15/08/2012(UTC)
Posts: 234
Location: Perth, Western Australia.
Ake, now you have me really interested.
Now just confirming, if you leave the crane magnet switched off for some time (several minutes) and then bring the screw driver close to it, then there is no attraction between the crane magnet and the screwdriver. However if you switch the crane magnet on and then power it off again and then bring the screw driver close to it within a minute or so then there is an attraction between the crane magnet and the screwdriver?

Regards....Chook.
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Offline Br502362  
#20 Posted : 10 October 2014 08:17:38(UTC)
Br502362

Finland   
Joined: 05/03/2014(UTC)
Posts: 680
Location: Finland
Originally Posted by: Chook Go to Quoted Post
Ake, now you have me really interested.
Now just confirming, if you leave the crane magnet switched off for some time (several minutes) and then bring the screw driver close to it, then there is no attraction between the crane magnet and the screwdriver. However if you switch the crane magnet on and then power it off again and then bring the screw driver close to it within a minute or so then there is an attraction between the crane magnet and the screwdriver?

Regards....Chook.


Hi Chook,

Just like that.

Regards
Åke
Offline Tom Jessop  
#21 Posted : 10 October 2014 11:08:01(UTC)
Tom Jessop

Australia   
Joined: 14/12/2002(UTC)
Posts: 800
Location: Newcastle NSW Australia


What happens if you leave a metallic object [screw or nail ] which has been attracted to the magnet & then turn off all power to the crane & not just the magnet coil ? With all power removed from the crane the object should drop immediately < if it does restore all power & try again & then just remove the power to the magnet . Again the object should drop immediately . Try again& remove power at the switch box for control of the magnet . I have the feeling there is a problem with a sticking contact in the circuit for the magnet . I dont have a crane to experiment on & have never looked at their circuitry but would think it would be similar to the early turntables . Try hitting the bench work the crane is sitting on & see if that drops the object , this might indicate a sticking contact somewhere .

Cheers Tom in Oz
Offline Tom Jessop  
#22 Posted : 10 October 2014 12:26:27(UTC)
Tom Jessop

Australia   
Joined: 14/12/2002(UTC)
Posts: 800
Location: Newcastle NSW Australia


The magnet has pin tails on the cable end , are they the same size as normal "M"plugs ? You could wire up a lamp to plug into the socket for the magnet & see if it stays on when the magnet is de;energised at the control panel . Could also use a multimeter to see what happens .

Tom .
Offline Br502362  
#23 Posted : 10 October 2014 13:48:46(UTC)
Br502362

Finland   
Joined: 05/03/2014(UTC)
Posts: 680
Location: Finland
They are normal M plugs.

Must try with a lamp and with a multimeter too.

I'll be back on Monday with some results... or more confused Confused

Regards

Åke
Offline Br502362  
#24 Posted : 14 October 2014 09:29:29(UTC)
Br502362

Finland   
Joined: 05/03/2014(UTC)
Posts: 680
Location: Finland
Hi all Smile

De-magnetized the cranes magnet once more and it works now perfectly!

Rgds

Åke
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