Turntable wiring...

[Russ Fleischman]

I am using a phono plug as a pivot and for wiring on my fiddleyard turntable and was wondering if anyone has a simple wiring scheme for changing the polarity?

 

Thanks and happy new year!

Russ

[naugytrax]

Hi, Russ: I'm afraid there is no simple way to switch the polarity of the deck rails automatically if you are using a jack plug and socket to carry the current. (This may be why no-one has replied to your post in a week!) You can of course switch the feed manually with an ordinary reverser made from a DPDT switch with the outer terminals wired "criss-cross".

Most commercially-made turntables (e.g., PECO, Heljan) switch the deck current automatically by feeding the deck rails through some sort of 180 degree segmental commutator-like feature rather than the 360 degree contact which you are using.

If your turntable is to be provided with automatic indexing then probably the indexing logic could be arranged to swap the deck rail feeds at appropriate times. But this would hardly be "simple" - at least, by my standards!

[BR60103]

Russ: the only way to do it is manually, with a separate direction switch.

Make sure you have something distinctive at one end (control cabin, winding levers) and set your reverse switch so that you point the switch towards the distinctive end. (You can sort it out by rotating the switch after it's wired).

[cromptonnut]

If you were using DCC, you could use a reverse loop module to feed the deck, and it would switch automatically.

 

I'm assuming you aren't using DCC, anyway. I don't think DCC reverse loop units work with normal DC, although one or two mentions of the "Hornby R8238 Reverse Loop Module" online say it will - however it's not listed on the Hornby website documentation as doing so.

 

Can anyone else confirm that it works? I wouldn't recommend spending ??25 to find out it doesn't

[Kenton]

As there is no such thing as continuous running on a turntable - the loco has to come to a standstill

Normally a dpdt switch is used to indicate the end facing the input track power.

 

I would normally opt for the power from the TT to control all input track sections (the same switch and feeds control power to all input tracks - each input track being sectioned from that supply - not from the points into the yard.

 

However, there is a way of switching polarity automatically.

use a dpdt relay with a coil that is driven from the power to the input tracks.