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· Just another modeller
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QUOTE (zmil @ 22 Jun 2008, 11:19) <{POST_SNAPBACK}>I have converted a fair few old locomotives ,mainly Fleischmann and Roco
The 70's Fleischmann Locomotives have the motor body electrically connected to the -ve motor terminal
and in most cases to the chassis.The chassis is the conductor for the lighting circuit.
Easy fixed for DCC conversion by the fitting of a replacement motor shield which is insulated (Flm part no 504730)

My question is .

With the Electric Locomotives , that have a working pantograph pick up system , the motor electricals are reversed.The positive motor terminal is electrically connected to the body of the motor , but the motor bogie has no electrical connection to the track. The wheels are insulted from the axles.Power pickups from this bogie are on the +ve side but are connected to the switch for selecting Pantograph power or Track Power.I hope I have described that OK

When converting to DCC -Disconnect any power pickup from the pantograph.Motor isolated from any track power pickup etc.

The questionable bit!

The Orange wire from the Decoder +ve connection of the motor (to save $17 + Frt) not using the insulted motor shield.The motor body is now electrically connected to the Orange wire. I have made sure that any metal component Cannot accidentally contact the motor (insulated the weights etc) The metal chassis is connected to the -ve side of the power pickup to run the lights with the original connections on half wave power.

I have 3 E Loks that have been done this way with no grief - So Far

Should I leave them as they are or should I use the Insulated motor shield?

***The risk is up to you: I would never do this with a clients locomotive.... or one of my own. Murphys law is too often proven right.

What you are doing is technically correct but practically risky to a degree.... The decision is yours.

A similar catch 22 can exist with older US Brass where pickup is shared by chassis/live wheels one side of the loco and other side of the tender, with an insulated drawbar between them... if two are coupled using metal couplers then a loco to loco short can happen... I've actually seen a Kadee red hot because of this problem!

With your current method it does of course work but you are at a much higher risk of decoder death.... ie:

(1) Any derailment that connects body/chassis to track in any way will possibly damage the decoder (orange touches track power).
(2) Any metal part of one locomotive wired conventionally touches a metal part of a non-conventionally wired locomotive (ie buffer to buffer) and a path will possibly exist from track to orange wire.

Kind regards
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