Sun 2/120: Problems booting from SIO-A

[Robert E. Seastrom]

My roommate and I have a Sun 2/120 with an external Ampex Capricorn 165 on
it (the drive is newly formatted and has nothing on it).  Much to my
chagrin, when I tried to fire it up, I discovered that the monitor has
ceased to function.  "No prob," I thought, "You're supposed to be able to
boot these machines by hooking a terminal set to 9600 baud up to the SIO-A
port via a null modem".  So that's what I did.  I turned on the machine,
with the keyboard and the monitor detached.  I didn't get any output to
the screen of the terminal (I understood I was supposed to get something
in the way of a Boot prompt).  Undaunted, I typed "bvmunix" at it, and saw
the drive take off for about 15 seconds.  Now, my questions go like this:

1) Was I supposed to get some kind of output on the terminal, or does that
only start after Unix is up and running?

2) It crossed my mind that the RS-232 line driver may have died, but I
couldn't find any 1488 or 1489 chips on the CPU board (where serial ports
A and B are).  If this is likely to be the case, what chip(s) should I be
looking for?

Thanks a lot...    if you can help me, please E-mail, as the net has been
gratuitously dropping my connections while I read news and I might miss
your post.

                    ---Rob