Okay, so I scoped the serial line, and the EIA line drivers seemed to be
acting funny, mark voltage was way to high, etc. So checked power, and
looks like I have a -15V distribution issue to the SPC slots on my
backplane. Moved the DL11 over to my DD11 expansion where I already
debugged -15V to get MOS memory working and then everything was fine...
Somehow the VT52 could still make sense out of the wacky transmit
voltages, but my MacBook certainly could not. Anyway, after this I was
able to run pdp11gui under wine on the MacBook and successfully connect
to and interact with the 11/45.
--FritzM.