# Turntable



## Zootdad (Aug 31, 2013)

Is a reversing module needed for a Walthers 933-2850 turntable ??? Thanks in advance.


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## DonR (Oct 18, 2012)

Thot someone who actually has one of these turntables would post
an answer.

I don't know how the track on the turntable is wired, or if it has a wiper
that picks up power from the track where it is stopped.

The answer to those questions would enter into a correct response
to you.

A reverse controller for the turntable track would be required if you wanted it to be
automatic. You could use a DPDT switch to control the power
to it, but you would have to remember to do it.

Don


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## Zootdad (Aug 31, 2013)

Thanks Don. I would think 100s of forum members have the Walthers turntable. Hope someone chimes in.


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## wingnut163 (Jan 3, 2013)

i will look in my NEW one and see if it says that the reversing module is needed.

glad you brought this up. now i need to see for my self. mine is DCC on board so i will check.


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## Zootdad (Aug 31, 2013)

Thanks Wingnut. Please let me know. Mine says DCC compatible also. BTW...I am over in Hopewell.


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## DonR (Oct 18, 2012)

I was surprised that there was little technical information available
on this turntable. Google turned up dozens of dealers for it but
I found several pages later a short discussion that was not
that informative.

The turntable track can be turned 180 so when it comes back to
the 'source' track it is out of phase to that track. Something will
have to match the polarity and usually that is a reverse loop
controller and it does it automatically.

If no controller, you'll need to use a DPDT switch with the turntable
track connected to the center tabs. Track power to one outer set
of tabs, then an inverse ( X ) of that power to the other set of tabs.
Flipping when loco is ready to return to source track would match polarity.

But then, you would also have to know the polarity of each 'round house'
track and before long you have a carnfoosing mess on your hands.

Go with a controller.

Don


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## wingnut163 (Jan 3, 2013)

well mine is all ready DCC. 

there is no mention on a reversing module but, it does state that there is a sensor on the table and one in the pit. so i am guessing that it changes the polarity.
this sensor must bet set for the table to be able to program the stops.

will read over all the info a couple more times to make sure.


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## DonR (Oct 18, 2012)

One way to find out for sure. Power the turntable track and
system. Check the
polarity against the track current by touching a multimeter set
to AC volts to one rail of table track and main where they butt. If meter reads somewhere near
17 or 18 volts it's not matching polarity (phase) and would
need a controller. Now run a loco across the gap onto
the table. If
it doesn't shop there must be a 'short' sensor in the
turntable system that matched the phase.

Turn the table 180. Run the loco back onto the main.
If it still works, you're home free. If it causes a
system short, you need a reverse controller.

Don


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## wingnut163 (Jan 3, 2013)

right.
but it is still in the box. so that will have to wait.

in reading again, the 0 position (censor) tells the table to move to #1 track. this one can NOT be changed. and all other track address will be set off this spot. so i am thinking that the censor is the switch to change the polarity.

there is a command that will turn the table 180% passing the censor.


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## fcwilt (Sep 27, 2013)

The bridge changes polarity at the location on the rim where it say you cannot place track.

Just the same when using DCC it's safe and simpler to install a auto-reverse unit on the power feed to the bridge. Then no matter how you wire things up it will work.


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## Zootdad (Aug 31, 2013)

Thanks everyone for your input. Very helpful. Much appreciated.
Zoot


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## wingnut163 (Jan 3, 2013)

fcwilt said:


> The bridge changes polarity at the location on the rim where it say you cannot place track.
> 
> Just the same when using DCC it's safe and simpler to install a auto-reverse unit on the power feed to the bridge. Then no matter how you wire things up it will work.


i see no benefit in doing double work/money if it is all ready set up to change polarity.
when i get to install it?? i will post the results.


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## DonR (Oct 18, 2012)

Yes, Wingnut...

When you get it hooked up let us know what is
or is not needed to maintain phase for the
table track.

Then, you can be the guy who helps the next buyer
who is in a quandry. 

Don


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## fcwilt (Sep 27, 2013)

wingnut163 said:


> i see no benefit in doing double work/money if it is all ready set up to change polarity.
> when i get to install it?? i will post the results.


Double work? Installing a reverser? Hardly.

And considering the cost of the lumber, track, rolling stock, decoders, scenery materials, etc, etc, etc another reverser is a drop in the bucket.

And if you make a mistake in wiring one or more of the stall tracks your covered.

You don't need one, it just makes things simpler, that's all.


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## Southern (Nov 17, 2008)

fcwilt said:


> Double work? Installing a reverser? Hardly.
> 
> And considering the cost of the lumber, track, rolling stock, decoders, scenery materials, etc, etc, etc another reverser is a drop in the bucket.
> 
> ...


Wingnut is right. If it is built into the controler of the DCC ready turntable, why add another one. The turntable that I have is not DCC ready and will have to have one added.


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## fcwilt (Sep 27, 2013)

Southern said:


> Wingnut is right. If it is built into the controler of the DCC ready turntable, why add another one. The turntable that I have is not DCC ready and will have to have one added.


There is no reverser in the TT, just a split-ring commutator that switches the feed to the bridge rails at a certain point in the bridge rotation.

While it will certainly work without a DCC auto-reverse unit, you have to pay close attention to wiring your stall tracks to be sure they match the "polarity" of the bridge at each location.

If you go ahead and install the DCC auto-reverse-unit feeding the bridge then it doesn't matter how you wire the stall tracks. It's just one less thing to worry about.


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## Santafe_man (Mar 18, 2014)

I'm jumping on this old thread as it's the first one I have found which relates to the question I have.
I have a Walters turntable with about 20 roundhouse track sidings around it. I have just DCC my layout. I get a short when the loco drives off the bridge into a roundhouse siding because the polarity is the opposite.
Can I install one auto reverser on all siding tracks or just install it on the turntable bridge?

Thanks, John.


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## fcwilt (Sep 27, 2013)

Santafe_man said:


> I'm jumping on this old thread as it's the first one I have found which relates to the question I have.
> I have a Walters turntable with about 20 roundhouse track sidings around it. I have just DCC my layout. I get a short when the loco drives off the bridge into a roundhouse siding because the polarity is the opposite.
> Can I install one auto reverser on all siding tracks or just install it on the turntable bridge?
> 
> Thanks, John.


Just install it on the bridge.


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## vikramgoel (Mar 2, 2015)

Hi,

I have both the 130' and 90' turntable with DCC and both have reversing controllers built in, there is no need to add another reverse loop controller.
Regards,

Vik.


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## fcwilt (Sep 27, 2013)

vikramgoel said:


> Hi,
> 
> I have both the 130' and 90' turntable with DCC and both have reversing controllers built in, there is no need to add another reverse loop controller.
> Regards,
> ...


Are you talking about the split-ring commutator that changes the bridge polarity at those points on the circumference where stall track are not allowed?

Or have they done away with the split-ring commutator and installed an auto-reverse unit?


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## vikramgoel (Mar 2, 2015)

fcwilt said:


> Are you talking about the split-ring commutator that changes the bridge polarity at those points on the circumference where stall track are not allowed?
> 
> Or have they done away with the split-ring commutator and installed an auto-reverse unit?


They still have the split ring, however as the loco polarity changes there is no need to add a reverse loop controller, the only care you need is to align the turntable so teh 'zero' stall point is not aligned to a track.
Regards,

Vik.


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## Brakeman Jake (Mar 8, 2009)

You shouldn't need a reverser if the turntable is installed correctly.Unfortunately,
instructions are often confusing at best.If I try to explain in writing,I'd probably be just as confusing.
The best would be if you could post a drawing (rough sketch will do) showing your setup,identifying wich track does what (with numbers) like roundhouse tracks,arrival and parking tracks.We'd also need to know where the "no track" areas are.It's not that hard to understand...just near impossible to explain in writing.


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## DonR (Oct 18, 2012)

Yes, Jake is right, the wiring of connecting tracks to a turntable
is important. A pic or drawing of what you have would be helpful.

Don


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## fcwilt (Sep 27, 2013)

Which is why I installed a auto-reverse unit - no need to worry about the wiring of the stall tracks.


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## DonR (Oct 18, 2012)

fcwilt said:


> Which is why I installed a auto-reverse unit - no need to worry about the wiring of the stall tracks.


Too Shay.

Don


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## fcwilt (Sep 27, 2013)

DonR said:


> Too Shay.
> 
> Don


"Too Shay" - nice play on words.

It's not like I went out an bought an auto-reverse unit just for the turntable.

The ones I used on my layout came 4 to a pack so I had a unused unit. So I used it rather then worry about the stall tracks and which should be which polarity.

It paid off in the long run. 

I got so frustrated with the Walthers DCC controller and the flaky commutator in the turntable, I redesigned the turntable electronics, used a commercial sealed commutator, added loco position sensors on the bridge, etc.

Quite happy with the TT now.


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## DonR (Oct 18, 2012)

You must have a Digitrax PM 42. That is one very interesting
device. It can be 4 reverse loop controllers. And all for the
price you would pay for one Rev. loop controller by
some other makers. 

Don


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## fcwilt (Sep 27, 2013)

DonR said:


> You must have a Digitrax PM 42. That is one very interesting
> device. It can be 4 reverse loop controllers. And all for the
> price you would pay for one Rev. loop controller by
> some other makers.
> ...


I am aware of the PM42 but, unless it has changed, it uses relays.

The ones I use are PSX-AR which does not use relays.


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## DonR (Oct 18, 2012)

I've seen other modellers who wanted to avoid the relays in
reverse controllers. They said they thought them too slow
in the Phase change. I use the Bachmann reverse loop controller
that does use a relay but I don't see any light blinks or loco pauses when
it operates. I guess I'm asking, is there any other reason to
go for solid state switching as opposed to relays?

Is there a price advantage either way?

Don


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## fcwilt (Sep 27, 2013)

Well the PSX-AR units are certainly more expensive.

But I like the design better - no relays, no power supply, screw terminals for wiring, etc.


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## Santafe_man (Mar 18, 2014)

I ended up purchasing a auto reverser & wired it to the turntable bridge rails & it has solved the polarity problem with the stall tracks.
Thanks for everyones advice.

John.


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