I have a  HO switching layout using a DCS controller and wifi. Both work just fine.  Due to a 'short', fixed 1 is now none functional, with the message 'cannot find TIU'?  I moved power-in and power-out to fixed 2 and everything works great. I checked all TIU fuses and they are fine. Changed back to 'fixed1''and  everything was again none functional. According to ' DCS COMPANION 3' the problem is in 'fixed1' channel. Is there a reset involved or do I have to return the TIU to MTH? The answer may be in Barry's book, but I couldn't find it. (the answer that is, not the book....lol)

comments very appreciated.






Last edited by JimRK
Original Post

If you're getting power out of FIXED #1, and it's just not seeing DCS locomotives, it'll probably have to be repaired.  Of course, this assumes you have enabled DCS on the channel.

Menu/System/ Dcs set up/ AON....... turns the  dcs signal on to all channels.... He must be using an aux power supply if Fixed 2 works?

Barry Broskowitz posted:

Check the fuse for Fixed #1 inside the TIU. Look at pages 159-160 in The DCS Companion 3rd Edition.


Before opening the TIU, Couldn't he just unplug power from the AUX power input and test to see if the TIU will power on through FIXED 1 input? If it powers up, the fuse must be good, right?



From his comments, I assumed that the channel had failed completely. That would make a fuse the prime suspect.

I also assumed that the TIU had a fuse since the tone of his response was that he recently acquired the TIU. That would argue that it was a newer model.

Lastly, I was pressed for time...  

Thanks for the responses. I've had the TIU for several years. It is version 'I' and was returned for a factory upgrade. MTH suffixed a silver dot to the 'I' verifying the upgrade. It has always worked flawlessly and yes, I do power it through the aux port.

When I power up Fixed 1-in, my voltmeter shows nothing coming out of Fixed 1-out (dead channel?).  I opened the case removed the fuse and it is fine. I switched fuses around between 1 and 2 to see the result. Same thing as before, power up Fixed 1 and no power coming out. Power up Fixed 2 and power out is fine.

Last edited by JimRK

What version is the TIU?  Look on the bottom of the case.  If the fuse is good, you should at least get power through the channel.  Other things that can affect it are loose nuts on the input and output connections or an overload has cooked a trace on the board.

John you may have nailed it 'fried trace'. When testing with my voltmeter I removed the 'power-out cables' and took readings right on the terminal posts. This sounds like it will have to go back...Advise!

If it's a Rev. G ( no version on the bottom ), don't bother.  MTH doesn't fix these, they're a "write-off".  I have one with the same issue, it's now a 3-channel TIU.

When ALL channels are set for DCS, will ALL channels send out a watch dog signal or only the fixed channels ?

All channels will send a WD if they're all configured for DCS.  It's controllable on a per-channel basis fixed or variable.

I just  run HO which means DC only voltage to the tracks and can only be done on fixed 1&2. The variable channels do not handle DC to the tracks.

As John says, I now have a 3 channel TIU.  I'll run the layout on Fixed2. If for some reason (not fuses) it becomes a 'dead' channel, I'll probably get a 'L' or newer model. The cost differential between a repair (plus shipping costs- I live in Canada) and a new one, would probably justify 'new'.

Thank you all for the help.


I must have a bad TIU then John. If I power the TIU via AUX and set all channels for DCS, using a brick connected to the variable channel input and out put to the track, my engines will start upon powering up the variable channel.

GUNRUNNERJOHN or Barry....I did notice on p.48 of 'COMPANION 3' under DCS SETUP, that a 'variable channel' can be changed to a 'fixed channel'. I ASSUME if my remaining Fixed-2 became dead (ie cooked trace), I could then set a variable to fixed (this would give  me 2 more fixed channels). Ido not run conventional only command.  It may seem like a silly question but then again this is DCS and Mr Murphy is always lurking.  Again, thank you all.

All that setting does is start the channel out at full throttle.  It's still a variable channel and needs all it's hardware to function.  If you're in "fixed" mode on variable channels, you can drop into variable mode simply by selecting the channel with the TR key and changing the voltage.

Obviously, if you never select the channel with the TR key and change the voltage, it'll act like a fixed channel as you suggest.

Last edited by gunrunnerjohn

John, I did a factory reset on the TIU and now I'm getting the watch dog signal on the variable channels.

Odd, if you had previously turned them all on, but sometimes a factory reset cures ills that aren't apparent.  All's well that ends well.

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