DCS Voltage

18 volts is the standard for TMCC, and many TMCC locomotive manuals caution against running any more than 20 volts.  18 volts works well for DCS as well, so that's where I'd run it.

most of the time i run at 16v. the trains run just fine, but i do use 18v for some engines, they run better that way---

The primary reason I use 18 volts is for TMCC, some couplers won't open every time on 16 volts.

Always test voltage output before using if you can. I bought a transformer today from my local electronics store.  120V AC input. Rated output 16.9 V AC. Clearly labeled. I tested output voltage before using it on my command control and it was putting out 27.9 V AC. I'm very glad I tested it before using. 

Thanks fellas!

What transformer was it? If it has a chopped sine wave oiutput some meters will not measure it correctly.

Dale H

Did you test it under load, some transformer use a small feedback current to regulate.  G

I recommend against using any power supply but one with a pure sine wave.  During a power outage, I plugged my Dell laptop power supply into a "modified sine wave" inverter, and blew the Dell charger/adapter.  A modiifed sine wave input to a TIU does cause issues with VARIABLE output wave forms, which is why the use of a Z-1000-type controller on the input side is not recommended.

I wonder if it's possible that Jeff's transformer's output rating was based on voltage at full load, which is not a good idea for rating a transformer.

I find that if I lower voltage below 14 volts, trains start to act weird, such as heavy load sounds coming on more readily.  The lowesdt voltage at which your trains run ok is probably the best, as that increases bulb life and reduces heat generated in plastic cars

When powering the tracks I bring the Z4K to between 16 and 17v.  Adjust the voltage to no more than 17v as loading trains to run.  All my engines have worked perfectly maintaining the 16/17v.  Even the TMCC/TMCC II, although only have 18 units of them.

But as John stated Lionel says 18v to assure coupler operation.  And some here have reported the need for 18v. 

So just experiment, BUT best to keep it no more than 20v.

I for one like to keep voltage as low as possible.

One further note: if you also run conventional, you will find that when having the voltage at 18 V with the track fed through a variable circuit, it becomes difficult to have the locomotives run very slowly.  The more the TIU has to reduce the output voltage the more it distorts the waveform, causing the locomotives to run faster.  For example if I feed 18 V into the TIU I cannot get a Docksider to run slowly--even at 5 V output it flies.  Reducing the input voltage substantially eliminates this problem.

You can also feed the lower voltage just to the variable inputs for conventional and still maintain the higher voltage for command operation.

Because you have no load on it, as soon you will put a load it will go to 16.9 volts 

Well I run DC power only on my DCS layout...30 volts for the last 7 years with no ill affect. PS2 boards will start acting up at 35 volts so at 17 volts you folks are just "tickling" PS2.

Sorry but I don't use TMCC...What is it?? 

18v to run TMCC/DCS on the same tracks.

I use a Z-750 brick, output 21 volts.  The DCS manual (page 13) says not to use the controller, so if TMCC engines don't like voltage higher than 18 volts, how do I lower the output of the Z-750 brick so I can run PS2 engines and TMCC engines (my new upcoming 3rd Rail E7)?

Specifically, Lionel says not to exceed 20 volts I believe.

Sounds to me like you have some weird interaction going on between your meter, the 750 controller and the TIU. I would suggest you remove the low voltage plug from the Z750 brick and connect it directly to the TIU input and see what that does. Cut the wire to the plug about one foot from the plug that way you can splice them back together if you wish.

Sometimes the only way to find things out is to just do it and see what happens. I think the risk is low.

Al

One thing for sure is that the TIU is not increasing the voltage, since it's not a transformer and has no circuitry to do so. The variable channels can lower voltage, however,  they cannot increase voltage.

AC wave forms other than pure sine waves can raise havoc with the accuracy of readings on normal AC voltmeters.

It should also be noted that the voltage shown on an AC voltmeter for a pure sine wave is substantially LESS than the peak voltage.  A 120-volt household circuit has a peak up around 170-180 volts.

This post is only a test...some apparently are experiencing difficulty adding to this thread.  My apologies for the interruption.