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Premium Member
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Discussion Starter · #1 ·
Well as I mentioned on the Warleys bargains thread, I picked up a "new" J39 from the Bachmann stand. Cosmetically it was perfect, so I joked with the guys on the stand "so this ones a non runner then!" which they all said quickly "oh no sir, we check them all before we re-sell them". I was doubtful but couldn't refuse the price.

Finally got back onto the layout tonight and what a shock....placed the j39 on the track and it shorted my dc controller straight away. Great. Well, in 20 minutes it was it was fixed. Well, first person to guess the fault correctly gets a prize!

Rob
 

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Rob,

On the assumption it was nothing obvious how about giving us a hint?
 

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Chief mouser
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11,775 Posts
Pick ups not making contact with the wheels or pick up wire not connected?

Regards
 

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In depth idiot
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Since these are on a split chassis (time for an upgrade Bachmann!) the usual is a piece of something conductive, usually metal, between the chassis halves; which causes a permanent short.
 

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Discussion Starter · #7 ·
QUOTE (34C @ 11 Dec 2007, 08:41) <{POST_SNAPBACK}>Since these are on a split chassis (time for an upgrade Bachmann!) the usual is a piece of something conductive, usually metal, between the chassis halves; which causes a permanent short.

Very close 34C, it is indeed a direct short across the chassis, but it wasn't caused by anything metal.....
 

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Discussion Starter · #14 ·
QUOTE (34C @ 11 Dec 2007, 20:45) <{POST_SNAPBACK}>Most likely conducting solid not a metal is graphite, a motor brush or piece of pencil lead for example.

Well well 34C you are on the money tonight!

When I started to dismantle the chassis I was amazed by how much lubricant had been used. In fact the entire area between the two chassis halves was covered to the point that it was coming out on all sides. As 34C has correctly guessed, stuck in the middle of all the lubricant (I did test the lubricant used for resistance and found it to have a small conducting property, not an ideal situation so I cleaned 99% of it off, leaving it only around the gear wheels) was a pencil lead! How it got there....

34C proceed to the top of the class, you prize is awaiting!

_____________________________________________________________________

Top of the class:

The prize is a link to the Railway Preservation Society of Ireland, a very interesting site with a good write up of the history of Irelands railways and the links with mainland UK, enjoy!

http://www.rpsi-online.org/contents/
 

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In depth idiot
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Strictly the prize goes to Mike Parkes for Carbon, without specifying the allotrope! Interesting site.

You did the right thing cutting down the lubrication, these split chassis perform best with just a light wipe of grease. As they age, I usually add a little powdered graphite to the axle bearings as this helps the conductivity as the plating on the stub axles wears away.
 
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