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rrman posted:

Are the latest greatest TIUs have this mod, or does the owner have to send in TIU, or is there a rev number letter to denote the additional diodes?

When the first mod that came out on rev L that added small smd TVS the TIU got a silver dot on the back by the Rev L sticker.  Not sure what is being done now.  G

I had the service bulletin preformed on my revision L TIU during warranty. The tiny TVS diodes were replaced with the larger ones per the service bulletin by MTH. 10 months later and so far so good. The worst derailments I've had have been a car wheel coming off the track through a switch and touching the center and outside rails, so nothing crazy. 

Ok, for 15 years or more I've been running DCS & along with Legacy, the past 4 years. Until 2 months ago my DCS was Ver 4.2, I had some running issues but not enough to drive me crazy, & I finally upgraded to Ver 6.1. I never paid any attention to my TIU REV version until this post. I have 3 TIU's, one REV L (works the best), one REV H1 & one REV13. Do all 3 of these need the TIU modification mentioned here?

Second question, I'm looking to buy another TIU (NEW) & want to avoid needing the modification, so, which REV to buy & is it available? I don't need a remote, & don't want WiFi.

Third question, what I have, is what I have & what REV versions should I stay away from? I only use one TIU on my main layout, the other 2 are back-up. Are REV H1 & REV13 junk?

By the way, I had a 4th TIU that fried completely years ago due to a derailment, REV 13. I have inline fast blow fuse protection & in this particular instance the fuse blew then re-welded itself then fried the TIU!

Last question, do any of these TIU's have internal protection?

My local hobby shop, I've known the owner 20 years, let me take home & test a NIB TIU, REV 13A, its VER 4.2. If I keep it, then I'll pay $175. I hooked it up to my test track & added engines no problem with 2 remotes updated to VER 6.1. I have a TIU that's REV 13 updated to VER 6.1 & when I try to add engines it takes 2 minutes, I get an out of RF range message then it adds the engine to the remote. Why a problem with REV 13 ver 6.1 & no problem with REV 13A NEW & ver 4.2. WHY??? If I keep REV 13A, will it need to have the TIU modification?

I'd appreciate if someone has some answers to this & my previous message.



The Mighty Barry is most likely rolling over and wanting to answer this. I will try. I do know Barry always told me to update ALL TIU's and Remotes to the Latest Rev. I have done that on my 625 sq ft layout and am more than pleased. Buying a new TIU does not mean it is the latest, I found this out the hard way! Latest is REV L. and even then it may need updating. As for what you have is what you have - UPDATE the software to 6.10 on all of them and the remotes you have. It is my belief that the newest TIU's do have some protection. Post a message to either Gunrunner John or GGG as both of them are excellent in this field. Hope that helps and I also run Legacy with my DCS and love it. I am not a huge fan of the legacy remote so tend to use the MTH WiFi app for Legacy but otherwise I love the DCS Remote. I Have four since there is talk of discontinuing them.

Sounds like apples & oranges are being mixed.  TIUs can't be upgraded from one Rev to another, but the software can be upgraded.  I have 2 ancient original issue Rev Gs.  One is running a grandson's layout in everyday use.  The other I can drop onto my layout when the Rev L has an issue.  Both Rev G's have the latest software, but they are still Rev Gs.  The Rev G had no overcurrent protection:  external fuses or breakers are needed.  All later models have overcurrent protection via internal fuses but I am of the opinion that they should be of lesser ampacity:  10 amps max.

The issues with Rev L modifications center about surge protection.  When there are shorts out on the line, especially derailments of moving trains, high-voltage low-amperage very brief currents are generated which can damage electronics.

Thanks for the suggestions. I may have mistakenly said REV when I meant VER, or visa versa. I do understand REV G is always REV G, etc, etc.

So is anyone familiar with where does REV 13 or REV13A fall into the order. Are they the very first? There is a REV13B on ebay. How many REV's have there been & what is the order they fall in. Obviously G is before H & so on where do the numbers fall into the order of things.

Yes, Barry must be shaking his head right now.

The very very  first was Rev G.  Unlike those that followed, it didn't have an internal fuse and all black terminals were connected internally.  Also, wires were soldered to terminals, not held by nuts.   As initially delivered, they had a bad circuit.  MTH fixed them under warranty and, at least for me, I have had no further troubles.

As to your problem, I suggest opening up the TIU case and checking the nuts that hold the wires to the through case screw terminals.  All of my TIUs, except the Gs, were loose.  I added an internal star washer and another nut to lock them tight.  Nut is metric, and stocked by Ace.  Sorry, I don't have the size right at hand.

RJR, Thanks again for your input. I've heard that about the loose nuts & certainly will check. What I'm still perplexed about is where the REV 13's fall in to place. First, middle, last...Good, bad, stay away from? Does anyone have a clue? I was told by one MTH repair specialist, REV13 were the first with NO fuse protection, I had one burn up.

I'm starting to feel, that like our engines, you buy it, cross your fingers, never de-rail, run it till it blows up, get it fixed or throw it away, buy a new one. That would be a great philosophy if it cost 20 bucks.

Lets face it, this stuff is sophisticated & mass produced & stuff will fail sooner or later. The less I know, the more I enjoy my trains. Ignorance is bliss.


I personally reached out to Gunrunner & GGG. John didn't have a conclusive answer saying he believed REV 13 is probably  REV. I3 (the letter I, not the number 1) & probably  came after REV H. So I have REV. I3, REV. I3A Silver Dot, would have followed REV. H.

I thank John for pointing out 13 was in fact I3 (clearly visible once I had my glasses on). See attached.

The silver dot after the REV. I3A indicates what?

Hope to hear from George.


Images (2)
  • REV. I3
  • REV. I3A silver dot

I forget what the silver dot signifies.

The service bulletin you are thinking of only pertains to Rev. L TIU models.

Service Bulletin 05-22-18a.pdf

As for the Service Bulletin, I'm personally not convinced it solves any problems.  I believe Adrian is of the same mind, and he spent considerable time analyzing the failures of the TIU's.  Adrian observed that the new "fix" described in the above service bulletin was getting slammed by transients at his location and the TVS parts were still failing.

I have designed a modification of a fix that Adrian made, it was pretty widely discussed in the DCS forum.  Adrian did the primary field work on this, but his fix was bulky and complicated to install.  This board was an attempt to provide the same protection in a much smaller footprint package with less connections.  I truthfully haven't had the time to follow up and actually kit up parts and make this a real thing, but at some point I may get to it.

This module perches right on top of the 74ACT244 chips that are the one damaged by the voltage transients.  This provides protection from high voltage spikes while not loading the DCS signal with the excessive capacitance of a TVS diode directly across the chip.  The Schottky diodes isolate the large TVS stray capacitance from the DCS signal while still allowing clamping of any damaging voltage spike.  Also, this module uses a TVS diode with three times the power rating of the "fix" that MTH is recommending.

I hope that answers some of your questions.


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Much of the early TIU mods even predates me, and while I am sure MTH trained techs at the time, some of that info never translated into accurate training bulletins that were distributed, though they may have been done by e-mail.  If you call MTH service, Don could walk you through it.

Having said that if a TIU is functioning correctly you are worrying about stuff you probably should not.

Rev L is the last Revision hardware wise and what should be purchased.  Runs on 6.10 Vers software.  The TVS mod is to protect the buffer transmit chips.

The first TVS mod could not hold up under multiple and frequent spikes.  Typically seen on large layouts that clubs run.  The second version used a larger TVS as a resolution.  Plenty of folks are running TIU with no protection and with no issues either.  Or at least non that effect running trains.

The TVS mod did apply to Rev L and Rev I3A.

I have had at least one TIU that when the mod was added the DCS signal was killed, but when removed it worked great.  No one can explain why.

If you are a smooth operator of a small layout with limited derailments and such your probably fine.  If your a little clumsy and frequently derail, or have many relays operating accessories on your layout that can cause spikes, you might want to have the mod done.

Of course if your already operating with some level of track suppression and good breakers on your power source, you are probably fine.  G

Exactly George.  I'm a little reluctant to put even the 500W TVS diodes in, they're right across the DCS signal, and they exhibit considerable stray capacitance, on the order of 1,000pf.  At 3mhz, that's a capacitive reactance of around 50 ohms, that's a significant shunt across the DCS signal.

BTW, according to the Service Bulletin 05-22-18a.pdf, it only applies to the Rev. L units.  Is there a newer release that includes the I3A version?


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I stumbled on something over the past couple of days, if this is common knowledge, please let me know. I now own 4 TIU's numbered 1 to 4. I have a REV L on my main layout #1. The other 3 are for my Xmas layout & back-up, since I hate to be unable to run my trains when I want. The back-ups are REV H, REV I3 & REV I3A with a silver dot. All have been updated to Ver 6.1 thanks to Alan Mancus selling me a used laptop at a reasonable price. I also have 3 working remotes & one with a bad LCD screen (anyone got a spare?).

Now for the discovery. This past weekend I purchased my 4th TIU a REV I3A with the silver dot which was address 1. It worked perfectly, I added engines no issue, & even made a few lashups to test if it was OK, all on my test track. Since the TIU on my layout already is #1, the REV H & REV I3 are #'s 2 & 3, I re-addressed the REV I3A (silver dot) to # 4. All of a sudden while trying to add more engines with I3A with my remote I'm getting "Out Of RF Range" messages & then it eventually adds the new engine into the remote. It takes 45 seconds to a minute to add the engine. Now I'm ****ed, what gives? When the address is #1, no issues & adding a new engine takes 5 seconds. So I change the address back to #1 & once again works perfect. Now I'm really ****ed!  I decide to take my other TIU's #'s 2 & 3 that always give me "Out Of RF Range" messages & change the address to #1. Low & behold, 5 seconds to add an engine & no MESSAGE!

It was a lot more involved than that, resetting the TIU's, deleting addresses, etc. to be able to figure this out, but that's it in a nut shell.

I always thought that the issues I experienced with my layouts over the years was due to some other problem, wiring, dirty track or what ever. I've been told, that the messages & other anomalies, are due to many possible things, user error, components failing over time, etc.

By the way, I switched the layout TIU REV L address from # 1 to 4 & then I got the dreaded "Out Of RF Range" message. So I switched it back to #1 and everything is beautiful! Go figure.

So my question is, did I miss something in Barry's multiple handbooks that everyone knows?

I'm thinking there is no point in having multiple addresses if you only use one at a time. Is that what I missed?


I'm no expert on TIU addressing, however, if I only used one TIU at a time I would make them all the same address and that would be #1. Sure seems a lot simpler to me to so it that way. 

I only have 1 TIU so I have never bothered to study the use of multiple TIUs or how all that works in Barry's books. If I get a back up TIU, which I am thinking about, it will be address #1 just like the one I have now so I can just swap them out if one needs repair.

It's been many years since I re-addressed TIUs, and my memory isn't as good as it was in the last century, but I seem to recall that if you take a new TIU, which comes with its address as #1, and readdress it as #4, all locos in the remote which had bene on #1 now move to #4.  The trick was to save the remote's data to a computer, re-address the new TIU, then restore the data from the computer.  The add the new TIU #4 to the remote.

I can't imagine wanting a layout in which only one TIU was used at a time.  While all remotes can have the same ID, my recollection is that TIUs should not.  Having gotten everythong set so it works, years ago, I no longer remember how I got there.

You are correct, the TIU's should not have the same address, that really confuses things.  The remote ID apparently doesn't really do anything as that's never been a factor.  I think it was intended to have some function that never happened, but that's just a guess.

Right now with my temp track and my workbench, I actually have two TIU's that are both #1.  I don't use them at the same time.  However, I occasionally forget to unplug the USB to the computer on the bench TIU, and when I try to run something, I get all sorts of no engine, can't find engine, etc. until I unplug the USB.


By the way, I switched the layout TIU REV L address from # 1 to 4 & then I got the dreaded "Out Of RF Range" message. So I switched it back to #1 and everything is beautiful! Go figure.

So my question is, did I miss something in Barry's multiple handbooks that everyone knows?

I'm thinking there is no point in having multiple addresses if you only use one at a time. Is that what I missed?


Changed the Tiu to 4 you need to change remote to read tiu 4. You can have it read multiple tiu's.

Of course. I would begin with a track read, the remote would search for the active TIU until found. Next I would try to add an engine. See attached images for sequence.

  • For TIU's 2 to 4 the remote would say, "LOOKING FOR ENGINE..."
  • After 45 seconds to a minute the screen shows, "OUT OF RF RANGE"
  • 15 seconds or more later, the screen would show that the engine was added.
  • I could start the engine & it would function normally.

    This would happen every time. Once I would change the address back to TIU 1, no more "OUT OF RF RANGE" messages with all 4 TIU's. This would be on the test track or on my layout. No signal issues with any TIU addressed as TIU 1.

    I'm happy with my results and observations. No point in having any TIU addressed other than TIU 1 if I never have more than one being used at the same time.




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Last edited by ironman1

Do you have more than TUI address set up in your remote? If you do, and they are not powered up and in range of your remote, that is the problem. The remote is looking for a TIU which it cannot find. The query takes time, as the remote needs to be sure it is not there. Once it is sure, it moves to the next address and repeats the process. 

You have several options, in no particular order:

1. Power up all your TIUs.

2.Tether the remote to the TIU. This should by-pass the process and go directly to the desired TIU. 

3. Assign a specific remote to a specific TIU.

4. Delete the TIU addresses in the remote that are not being used. If you choose this option, the engines associated with that TIU are deleted as well. If you go this route, back up the remote to your computer first. Then delete the others TIUs. When you need the other TIUs, do a restore from your computer. 




Hi Chris,

Thanks for your reply. I no longer have multiple TIUs in my remotes, only TIU 1,  I've deleted the extras & all TIU's are number 1. I enter my engines and record their addresses in a written log so there are no conflicts. At this time it is working for me & I have no need to utilize more than one TIU at a time.

I could try some of your suggestions but this approach is working for me. I may not have found a glitch in the system but there isn't a need for me to get something to work that I will never do. I don't know how many operators use more than 1 TIU at a time but the more complicated we make it the more problems seem to arise.

This all started with me trying to upgrade to VER 6.1 which I have on all my remotes & TIU's now & its working. I just want to run my trains with my Grandsons & friends.

There are a lot of ways to skin a cat & for me, I found a solution. Thanks again for your input.


George (GGG) replied to a personal email about this post, see below.

The remote has to search through all the TIU looking for engine which takes time.  If only one TIU, one search.

Any engine that was added to a TIU that is placed into Super TIU mode will operate on all of the TIUs that are in the DCS Remote, regardless of whether a TIU is in Super TIU mode or Normal TIU mode. However, any engine that was added to a TIU that is not in Super TIU mode, will only operate on tracks connected to the TIU to which it was added”

If it's were an original, it would not have internal fuses.  The original Rev G would not be worth fixing.  I'd ask GGG his opinion.

Does it short out transformer with all wires removed from output terminals?  That would pin it down to the TIU.  I would THEN remove wires from input terminals, one at a time, to pin it down to a channel.

Any remote ever made will work any TIU ever made (assuming they both work)

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