Thanks for the reply swoop223, this is an old unit, 2004 and you may not see it on their site, but that is the correct model number as per the data plate. I could not paste a pic of the data plate on this reply. I was not able to find any schematic data on this unit, thanks again for your response, if you find anything let me know.

are you sure about the model number?
piggyback/princeton only shows models beginning with PBxx
don't see anyting on their site related to Z2-3TX anywhere
are you sure this is a princeton/piggyback? or some other brand?