Hi,

Thanks for finding my pages useful.  I'd like to mention that though the 
data's there I haven't actually verified them all on my machine and I've 
been updating the page as I find out more about my machine and its OS (and 
I finally have my pmax again!).  I've still yet to find one of those mmj 
connectors and just about *this* close ripping out the mmj connectors and 
putting in regular 6p6 rj11s.  (Anyone in the US know a place that I can 
get MMJ connectors on cable ends cheap?  Gosh, I don't even want to know 
how much the crimper costs!)

Anyway, I believe you should be hooking up the serial console to the 
printer port, and that's why you were getting some garbage, it was trying 
to do something with it.  Maybe the serial settings are off (9600bps or 
whatever has been set in the nvram)?  Do you have both RX- and TX- hooked 
up to GND/Common?

There's a schematic here that looks like it's pretty close (and ties off 
more signals so that you won't have to worry about handshake problems.)

http://www.lammertbies.nl/comm/cable/RS-232.html#mmjs

Good luck and let me know when you get it working!