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Discussion Starter · #1 ·
When I hook up my track wires to my turntable controller the unit shuts down my DCC system when the turntable reaches one particular spot, either end. If I move the bridge just slightly it continues to operate until it reaches this spot again, either end. If I remove the track wires from the controller, the unit functions properly as far as moving from track to track without shorting out, but no track power.
Any ideas for fixing this problem?
 

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The turntable is what we call a 'reverse loop'...it turns a loco
around to go back where it came from. When the table revolves
the table track is reverse to the layout track. This causes a
'short'. The turntable has a built in automatic reverser to
avoid that. Check to see that you are using a separate power
supply to power the table motor. The track power of your
controller goes ONLY to the table terminals so marked.
Here is the manual:

file:///C:/Users/Don/Downloads/09330000002859.pdf

You would power the tracks of the 'round house' with
your DCC bus. Make sure all are same 'polarity'.

If this is the DCC model the wiring would be
different...

Don
 

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As I explained on the other site where you posted your question, the turntable has a split rail design. It momentarily crosses a gap where there is no power so that, as it moves past 90 deg either direction from the approach lead, the phase to the bridge rails gets reversed. This now places the bridge rails in phase with the lead once more in case that's the direction your engine will move, or it will move off the bridge and into a bay or onto a radial track next to the turntable's pit.

Note: it is very important to wire the bays and radials on either side of the 90 deg split the same way as the lead. Even though the bays are angled away from the lead (except for one directly opposite), and the radials that you may have are angled, they should all be treated as if they have the same general phase orientation as the lead track. Before passing 90 deg either direction, there will be no phase conflict. As soon as 90 deg are passed, and the DCC signal momentarily lapses, and then is restored, the split ring will have reversed the phase to the bridge rails. The decoder and your DCC command station won't care. DCC doesn't care if your right rail is 'positive' or 'negative'. It doesn't like both coming to one side of the decoder at the same time. One or the other. So, as the bridge rotates over the gap, and then power is restored, the DCC system doesn't care. It WILL care if the first metal tire bridging the gap between the bridge and lead/bay/radials is conflicted by mismatched phases. The reversal of the bride phase during rotation counters the phase conflict that would otherwise have been present. Now, all rails are back in phase.
 

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Discussion Starter · #4 ·
I have not yet hooked up my tracks, other than the tracks coming in. I am also sure that nothing is touching the bridge track, The DCC instructions say to hook up the two wires to the track input and the controller. Am I not understanding this?" The unit shuts down just as the bridge is leaving the "no track" area.
 

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Discussion Starter · #5 ·
The turntable is what we call a 'reverse loop'...it turns a loco
around to go back where it came from. When the table revolves
the table track is reverse to the layout track. This causes a
'short'. The turntable has a built in automatic reverser to
avoid that. Check to see that you are using a separate power
supply to power the table motor. The track power of your
controller goes ONLY to the table terminals so marked.
Here is the manual:

file:///C:/Users/Don/Downloads/09330000002859.pdf

You would power the tracks of the 'round house' with
your DCC bus. Make sure all are same 'polarity'.

If this is the DCC model the wiring would be
different...

Don
Thanks Don.
Yes, this is the DCC model. It shows the same two wires going to the track input and the controller input. The power shus down as the bridge is entering or leaving the "no-track" area.
 

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Discussion Starter · #6 ·
As I explained on the other site where you posted your question, the turntable has a split rail design. It momentarily crosses a gap where there is no power so that, as it moves past 90 deg either direction from the approach lead, the phase to the bridge rails gets reversed. This now places the bridge rails in phase with the lead once more in case that's the direction your engine will move, or it will move off the bridge and into a bay or onto a radial track next to the turntable's pit.

Note: it is very important to wire the bays and radials on either side of the 90 deg split the same way as the lead. Even though the bays are angled away from the lead (except for one directly opposite), and the radials that you may have are angled, they should all be treated as if they have the same general phase orientation as the lead track. Before passing 90 deg either direction, there will be no phase conflict. As soon as 90 deg are passed, and the DCC signal momentarily lapses, and then is restored, the split ring will have reversed the phase to the bridge rails. The decoder and your DCC command station won't care. DCC doesn't care if your right rail is 'positive' or 'negative'. It doesn't like both coming to one side of the decoder at the same time. One or the other. So, as the bridge rotates over the gap, and then power is restored, the DCC system doesn't care. It WILL care if the first metal tire bridging the gap between the bridge and lead/bay/radials is conflicted by mismatched phases. The reversal of the bride phase during rotation counters the phase conflict that would otherwise have been present. Now, all rails are back in phase.
Thanks. As I stated, the power shut down comes as the bridge is entering or leaving the "no-track" area. The instructions for DCC show the same two wires going into the track and controller inputs.
 

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the unit shuts down my DCC system when the turntable reaches one particular spot,
Are you sure about the terminology here? "The DCC system shuts down" (which would mean that the DCC command station is probably seeing a short) or is DCC power momentarily not available to the bridge rails on the turntable while in the "No Track" zones.

If DCC power is momentarily not available in those "No Track" zones on the included template, then the Turntable is performing as designed for the reasons which Mesentaria explained quite well. The split rail design MUST have a dead zone or else the DCC system would short every time and all the time.

Now, if the DCC system shuts down as you said in the original post, that is a horse of an entirely different colour. In that case, I would suspect that somehow the gap in the split rings is being bridged so that a short circuit between the two phases is seen at the DCC controller. This will take further trouble-shooting.

Steve J
 

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Thanks. As I stated, the power shut down comes as the bridge is entering or leaving the "no-track" area. The instructions for DCC show the same two wires going into the track and controller inputs.
Yes, as others are attempting to explain, the power goes out momentarily to the bridge rails, and if there's no 'keep-alive' capacitor on your locomotive's board, it will immediately go silent. If you have another sound locomotive elsewhere on your powered layout, you'll soon notice that it continues to operate seamlessly because power is still rising from the rails under it to the decoder. The locomotive on the bridge will fleetingly go silent, and then start up again as the bridge moves across the split rail gap and then makes contact with the 'far half' of the split rail. As soon as contact is restored, the phase is now switched to the decoder (which doesn't care) and the decoder will dutifully power up again and make sounds.

I don't know about all DCC systems (I use an ancient Digitrax DB150 command station), but if there's an actual short, it should sound out a warning, usually successive beeps. Also, if there's a short, the command station should shut down everything. Even your distant locomotive should lose power until the command stations senses that you have rectified the short OR shut off power to the command station. No warning...should be no short. It's just the bridge crossing the gap, and the other locomotive should continue making sounds and moving if you have given it a throttle input.

If you only have one locomotive, and you are confident in its behaviour being very reliably predictable as the bridge rotates, then remove it and place it on the other layout tracks. Make the bridge rotate over the gap in the split rail, and see if the locomotive dies where it sits. I'll bet it does not. This should help you to see that it is only broken rail power on the bridge, and that it is fleeting as the bridge rotates over the gap in the split power rail under it.

NOTE!! One other remaining fly in the ointment is if you have inadvertently powered one of the rails on the other side of the bridge. If the first metal wheel crosses the gap between the bridge rail and one, or more, radial tracks, and a short really does happen during that time, it means you have a phase conflict. You have wired the one, or both rails of that radial track, incorrectly. Swap them, and now you should not get any short indication from the command station.
 

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Discussion Starter · #9 ·
When I hook up my track wires to my turntable controller the unit shuts down my DCC system when the turntable reaches one particular spot, either end. If I move the bridge just slightly it continues to operate until it reaches this spot again, either end. If I remove the track wires from the controller, the unit functions properly as far as moving from track to track without shorting out, but no track power.
Any ideas for fixing this problem?
Got my problem corrected thanks to you guys. I hooked up a separate power supply to the controller and it works perfectly.

Thanks again for all your responses.
 
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