Been away from the trains and started up again and have a DCS problem.  Have 2 separate tracks upper/lower levels. Using Z-4000 transformer.  Fixed 1 for upper and 2 for lower level.  Ran train on lower level and was working but then slowed down and stoped.  Light flashing on transformer and I thought train was off track, but was not.  volts on transformer at 4.7 and light flashing when handle raised.  Checked all my connections to track and track itself but was not getting  power.  Finally narrowed it down to the fixed channel 2 in on the interface, which is my lower level.  Power from transformer to unit good, my upper level (fixed channel1) works fine. so power to channel 2 coming in is good the track from the fixed channel 2 is out.  Read in the manual that there are 20 amp fuses for the channels. Went to auto store got fuse and put in according to diagram in manual.  Nothing, still flashing light on transformer and when handle lifted, shows 4.7 volts as if a train is off the track.  So it seems to be that my channel 2 fixed out to track is not working at all.  What next ? any ideas out there what I can do to fixed the channel ?  Thanks.  

Original Post

Take a VOM meter and disconnect your tiu from layout and transformer. put ohm meter on continuity and check resistance across input of channel 2 fixed 2 input and read ohm should show infinity or no ohms at all the check 2 fixed output. you should again read infinity or no ohms at all! if either test you read 0.0 ohms you have a dead short across input or output. if the occurs you have a shorted tiu tvs diode across input or output channel. while your at it I would check all tiu input and output channels !  also check out transformer by itself to make sure its not a transformer issue. if you don't find anything wrong when you test your tiu as descried above check your tracks for shorts with the same meter. the reason I had you disconnect tiu was to avoid if it's a track issue or not!

p.s. you can check  the internal fuses , but they rarely blow ,but  if you choose to you have to take out 6 screws on the bottom of your tiu and then pull the top cover off, the fuses are yellow in color if your tiu does not have any as some versions do not have fuses reg G for instance . most common is rev L and it does have fusses! 

Alan

o gauge  trains ,music ,computer repair windows 7 and 10!

ASC Tech MTH school completed! 2019 !

He said he replaced the fuse.  Are the plastic terminal on Fixed 2 showing signs of melting?  You may have a loose internal connection to the output terminal, or input.  After Rev G they are nuts with lock washer, but if they become loose you might see the symptom you saw.  Especially if you draw high amps off the TIU.  G

MTH Authorized Service Center

Authorized ERR Dealer

Lionel Independent Repair Tech

Virginia Train Collectors Member

First I know its not a transformer issue since I had another extra transformer to use as a tester, and got power to the track.  No melting issues.  Using a low voltage tester with light to check terminals,  power is shown on all channels except the channel 2 fixed in, that channel shows not getting power and that's why I replaced the fuse. Could the unit go bad on one terminal ?  All was working fine until train stoped and shout down.  Thanks

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