Transformer Failure Possible Cause?

Does the doorstop still have vac output if alone?

Yes; Phasing?

No?; Bad luck?

Did you run input/output fuses? A filter? 

  Is this a standard single tap industrial transformer from the printer, or with a regulation board, muti-tap,...i.e. a large coil?; or just a component style board only?

Bad luck: Lacquer coatings on windings occasionally gets destroyed and transformers die. Heat cycling expansions vs metal gauge & quality of the wire are next in line to fail naturally by. 

Does it have 4a, or 4va? Stamped on the coil housing or on the printers back?

This is transformer similar to a MTH brick.  Output says 4 A.  Placing a meter in the track showed voltage of zero but that may or may not have been due to the power master.  Doesn't matter at this point.  Replacing the transformer got everything running fine.  The "doorstop" by itself only shows 7 volts output with no load.  It had previously provided 19V and ran this trolley loop just fine.  I could provide a picture of the offending piece but this isn't something to be fixed so there is no point.  I was just wondering why it would fail and if there was something to look for going forward.  I have a duplicate here at work that is on 24/7 and has no issues.  

  If it only puts out 7 volts now, there is likely a short in the internal windings wires.

Sort of like a variable transformer , it is tapped in a new spot along the windings.

  Likely it would have died soon anyhow, or it took a bad bump and tweaked during dissasembly.

In my experience, the ruggedness of small industrial transformers varies greatly.