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In short, an MTH TIU is not a power supply - it is a digital command interface.  The Track Interface Unit (TIU) is the brains behind the DCS system. Connected between the transformer and the track, the TIU receives signals from the DCS remote control and relays those signals to each train you are controlling via the rails. The type of signal relayed to the train depends on the operating mode at the time. If operating conventionally, the TIU will raise and lower track voltage to control engine speed. If operating in command mode, the TIU will send a digital signal to each train you are controlling via the track rails.

Pg 113 of the manual discusses operation of Conventional Locomotives using a DCS system with a TIU,

Pg 11 starts the section on wiring, including the use of classic transformers.

The manual itself:

As for differences, off the top of my head:

  • With a classic transformer, a pure sine wave signal is sent to the track. With command systems, most variable control is done electronically and therefore produces a modified sine wave to the track. This modified sine wave can cause some components to run warmer; This is seen as a benefit for smoke units. Note that this un-pure sine wave can be detrimental to some the operation of sensitive electrical components, notable some MTH PS1 locomotives are very picky in conventional mode.
  • With a classic transformer, the full voltage range can be directed to the track. Some of Lionel's transformers, this can approach be 24VAC. Common command systems such as MTH DCS is restricted to a voltage of ~18VAC.
  • Some classic transformers have a 5V boost to compensate for the additional electrical demands of the air whistle motor. The common command systems do not provide this boost.

I'm not disagreeing with cleaning brush dust and lubing as this coincides with increased voltage needs (cars too, clean those wheels oil any that need it (wipe oil on rust, brush, oil, wipe, repeat until clean, wipe well with an absorbant cloth. A little oil "darkness" is protection)

Some locos I have won't wake up until they have warmed up. It's nothing new to me. Warm ups were rituals for Gramps. The loco would sit until smoke got cooking, then it would get a good two or three laps alone on an 18x30 at LEAST before it pulled a load. 

I.e., yes I have to apply 100% of a 1033/15v 4a to wake up a few pre/postwar cast era locos.  Some cannot pull a load until they warm up. They also get run at full throttle most of the time. (same trains on a kw fly around, pull 25+ cars (I only have so much room) and can jump rails)

However, some engines do need more voltage when they wear too. Look that the axles dont wobble fwd/back; shift away from the gears (needs bushings?) Also note how the gears ride on their shafts. Worn will tilt off plane once side thrusts start. Eventually bad bushings/gears can bind out of sequence/lock up, esp. 6 driver PW. (gearposts can usually live a longer life with prudent gear changes)

I presume you are operating these locos in conventional mode, using the DCS remote, and through the variable channels of your TIU.

Disclaimer: It's been a very long time...  My TIU is one of the very first models, and I never upgraded the operating system beyond 3.xx.  But if I recall correctly, when using the variable channels, the indicated voltage on the remote's LCD display wasn't accurate.

All bricks are not created equal.  Which one(s) are you using?  Do you have a traditional transformer to compare against? 

The most important test:  if you put a volt meter on the rails when the train is running, what does it read?  How does that compare to what the remote is telling you?  Please try this test and post back with your results.

It's very possible that your locos are drawing excess voltage due to wear, or lack of maintenance.  But they could also be operating normally.  We can't tell unless we know the actual voltage on the rails.  Measuring it during operation with a meter is the best way to find out.

Last edited by Ted S

First off, when you dial up 14 volts on the DCS remote for a variable track, it's not necessarily really 14 volts.  The DCS remote assumes 22 volts input and divides it's speed steps up with that assumption.  It changes voltage in 1/2 volt steps, so there are 44 steps.  So, that 14 volts would equate to step 28.  Now, let's assume you are putting 17.5 volts into the TIU instead of their assumed 22 volts.  That means you're only putting 80% of the voltage that the DCS is assuming for track voltage.  The indicated 14 volts on the DCS remote is really putting 11.14 volts on the track.

Next, consider the vagaries of the chopped waveform generated by the TIU in the mix, and it's difficult to know what amount of energy you're really bringing to the table using the TIU to regulate the voltage.

Whether you're using two bricks and a TIU or a regular transformer to supply power to the track, it shouldn't make a difference how the voltage gets there - after all, 14v at the track is 14v. 

There may be differences attributable to internal voltage loss in each system and degree of accuracy, different wave forms and insuring the TIU is getting a full 18v to start with, but once those differences are accounted for and each system adjusted to insure 14v to the track, it shouldn't make a difference to your engine whether the 14v is coming from one or the other. 

Assuming you have the Lionel transformer to test with, I would first dial up 14v to the track through the TIU and measure the track voltage with no load (no train on track) and then with a load and then repeat using the transformer and compare the results. 


Last edited by Richie C.

Even your digital voltmeter cannot read the non sinusoidal wave form correctly, so your 9 VAC from your TIU, is probably not really equal to 9 VAC of sinusoidal waveform energy, out of an old just oil your trains and have fun running the old stuff with of the DCS...I've been doing that for years, but the old stuff needs a lot more lube attention than any of the newer stuff.  BTW, I'm an Electrical Engineer, that works daily with Variable Speed AC and DC drives....with and without encoder feedback. Also note the DCS doesn't read voltage, as noted above by John.

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