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I recently picked up a Revision L TIU in some stuff I acquired. I was testing it and it does not put out a DCS signal on any channel. I tried turning the DCS signal on for each channel using the remote with no change. Reloaded the DCS software and reset the TIU with no change. I'm assuming this is some kind of hardware issue. Is it possible to repair this TIU? If not no biggie, just curious if it can be fixed. 

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I did build a signal tester yet, but I should. I was using a PS2 locomotive on an isolated piece of track to test each channel on the TIU I just got. I tried two other locomotives (both PS3) and got the same result on each channel. TIU can't find the locomotives and the locomotives see no DCS signal on any channel. All 3 locomotives work fine with my layout TIU. 

Well, it sounds like you are probably right about the DCS signal.  The real question is it the input or output signal. 

Question: Do the locomotives come up in conventional mode like there's no output signal, or do they just fail when you try to add them to the remote?

The locomotives all come up in conventional on every channel. READ on the remote does nothing as well. I've also tried toggling the DCS signal on and off on each channel to no effect. The TIU can't find locomotives either. Says "No Engines to Add" when attempting to add a DCS locomotive.  

Coming up in conventional sounds like the transmitter chips have died.  Normally, they don't all go, but if one fails shorted across the 5V power, it kills most of the function of the TIU.  My top suspect would be the 74ACT244 parts, one for each channel.  Chances are good that not all of them are bad, the trick is finding the one that is dragging the rest down.

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