VAR 1 works for TMCC but VAR 2 does not?

If this is a newer TIU the commons are not tied together.  If the loops are separate and you only have the TMCC command base 1 wire going to VAR 1 common, you may need to add another to VAR 2 common from the TMCC base or tie the commons together between the outputs of the TIU.

Sam,

You have to set the START VOLTS and MAX VOLTS on VAR2

Ensure that the "one wire" from the TMCC Command Base is connected to the tracks of both Variable #1 and also Variable #2.

Martye:

Commons on the TIU:

Something that I didn't know.  During the switch: I had the TMCC command base wire connected to only one of the inner fixed (Red side) terminals and the TIU distributes the TMCC commands to the other outputs and all worked OK (including starting up TMCC engines).  Initially, I thought I needed the command base wire connected to each output side that I wanted TMCC to work but it appears that is not true (I'll do some more testing).

Also, Initially, I thought the power from one red output terminal going to another output red terminal would create problems with power distribution but that is not the case.  Guessing that since the grounds are separate, the output power regulation will remain isolated.  I have 3 separate loops of track that are all power independent. 

Joe,

I'll have to research how to set 'start voltages' and see if that works.

Barry,

As mentioned above, it appears that connecting just one base command wire to one output (I did the red/hot side) and the TIU seems to distribute the commands to all outputs.  I'll have to do some more testing to verify this.  Thinking about it, it seems like the ground side would be common to all terminals.

Correct me if I am wrong, but I think you stated VAR2 goes to  full voltage when you turn on the transformer, even though you have set it to zero?  IF you do not have control of voltage, the VAR2 channel has failed.  This is repairable.  If voltage has gotten too high on V2 that may be causing the issue with TMCC engines not responding.   G

samparfitt posted:

Martye:

Commons on the TIU:

Something that I didn't know.  During the switch: I had the TMCC command base wire connected to only one of the inner fixed (Red side) terminals and the TIU distributes the TMCC commands to the other outputs and all worked OK (including starting up TMCC engines).  Initially, I thought I needed the command base wire connected to each output side that I wanted TMCC to work but it appears that is not true (I'll do some more testing).

Also, Initially, I thought the power from one red output terminal going to another output red terminal would create problems with power distribution but that is not the case.  Guessing that since the grounds are separate, the output power regulation will remain isolated.  I have 3 separate loops of track that are all power independent. 

 

The one wire from the TMCC base has to go to the commons, which is connected in theory, to the outside rails.  If not, the TMCC engine will not perform as they should.  They are expecting to see that part of the signal on the common (outside rail).  And in the case of the newer TIUs that means you need to tie the commons together or supply the one wire connection to all commons, basically doing the same thing via the TMCC command base.

MARTYE,

I moved the command base wire to the ground side, which makes sense. 

I have to agree with GGG in that the TIU is, probably, damaged.  Possibly due to me connected the command base wire to the hot side. 

I had the initial issue of DCS, last year (before buying a new one), and it was not functioning properly.  I bought some surge suppressor diodes from TMC to try to fix it, but it was academic as the board was shot.  I have a surge suppressor diode left and can try replacing the old one and see if that works. 

FYI,

The initial surge of 22 volts doesn't appear to confuse the engines on that track as when I dial in VAR 1 with a starting 22 volts (and not zero volts), the engines behave properly (ie idle with no sound or movement).  Thus it does, indeed, appear to be a damaged TIU.  Not too happy about that as I just bought it a year ago.   Again, it may have been my fault connecting the TMCC command base to two hot output sides (although that could easily be done by mistake on many TIU's!).