I'm helping my grandson with an HO layout. We got a Walthers turntable installed with a motorizing kit that require 12 volts max. He's got a
power unit to run the train but the auxiliary output is rated at 15 volts. We also need a rheostat of some kind to operate the table?
We also have two Atlas # 65 undertable switch machines mounted and the proper momentary control boxes for it but the instructions do not give a voltage range.
Grandpa Ben
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Which is more than 12 volts.

It's an indexing turntable. Which means it will move in a series of steps. A rheostat may give you better control of it, but it is not really necessary.

I have used them with many different voltages up to 16 volts. But watch out, they will burn out if you power them for too long on any voltage.

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[...]
Do not use the auxiliary output for the turntable motors. Note that the turntable motors need DC (direct current), not AC (alternating current). The "auxiliary" or "accessories" terminals outputs AC. The turntable motors need DC so they can be reversed with a direction switch (which interchanges the + and - of the DC.)
Your best bet is to buy a good power pack for the trains, and to use the train-set power pack for the turntables (and lights, turnouts, etc.) It's not advisable to use one powerpack for everything. MRC's Railpower series start at around \$30-40, and are worth every penny.
I would also suggest you get a basic wiring book, such Wiring Basic (published by Kalmbach.) There are others. It's worth a trip to a hobby shop, IMO, even if it entails a half day excursion. But you and your grandson will have a great time in the shop looking at all that cool stuff.... :-)
HTH
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We have a Tech 4 MRC 200 for the trains so from what you are saying we just need a separate 120 AC to 12 VDC transformer for the turntable and turnouts? Gordon wrote:

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Ben wrote:

For the turntable, you need controllable 12V DC.
For turnouts, you need 14-16V AC. You also need momentary switches, such as spring-loaded pushbuttons. (Atlas makes a clunky but effective turnout control switch with a spring loaded slide switch.) 12V DC will work, but AC is better, because the 60Hz buzz in the solenoid is more likely to jog loose a slightly stiff throwbar and make it move.
A second powerpack will do the trick. You don't need a Tech 4 for this, any powerpack that puts out about 17VA total power will do. (That's about 1 amp max on one circuit or the other, but not on both at the same time.) Trainset powerpacks typically do this, so if you can find used but functional one, you're set. Otherwise, buy Railpower pack, it's cheaper than a Tech4.
HTH
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Thanks Wolf that clears it up for me. We have the Atlas momentary switches with the # 65 undertable Switch machines but there is nothing on the box or in the instructions as to voltage range or indeed the information that AC can be used. Wolf wrote:

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