Turntable polarity Help

Discussion in 'HO Scale Model Trains' started by TrainJunkee, Jul 31, 2007.

  1. TrainJunkee

    TrainJunkee Member

    I am using the old walthers 90' Turntable and I am run DC trains until I can afford to go DCC. When I aproach the turntable, If I dont have the track facing in the right direction to match the approach track's Polarity it shorts.. Is there some wiring trick so I can have the polarity miss- matched from the approach rail
  2. steamhead

    steamhead Active Member

    You need to wire the turntable using a reversing switch - a DPDT switch wired so it reverses the polarity of the output.
    that way you can match the polarity of the approach track and the turntable track. You can also use one of the automatic reversing modules that will set the polarity automatically if it senses a short circuit.

    Good luck..!!
  3. 60103

    60103 Pooh Bah

    If you go the manual switch route, you need to mark one end of the turntable so that you know which way to throw the switch. Sometimes there is a little platform or control booth at one end, other wise you may have to paint something.
    The switch needs to be fed from the approach rail or the block switch that covers the section the roundhouse is in -- that is, after the main direction switch, so that when you reverse the direction, the loco can come straight off.

    The DCC black box will solve this problem but only when you adopt DCC. We really need a box like that for DC.
  4. MasonJar

    MasonJar It's not rocket surgery


    Did the turntable come wired already? If yes, it may use a wiper system to power the rails - it should be a match for the approach tracks all the time, because the wipers will be set up such that the polarity reverses as you rotate the table. (This is the way the old Atlas TT is wired too.)

    So - Is it shorting no matter which end of the table is at the approach track? If yes, then reverse the existing wires from the turntable. That should solve the problem.

    If it is not pre-wired, then you may have to adopt one of the methods above.

  5. steamhead

    steamhead Active Member

    Hi...I have a 90' Walthers (the kit version) and it is not self reversing (like Atlas' table). I use a reversing switch, and the little booth as a guide as to which way the switch needs to be thrown....

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