Debugging modem on 3620

[Paul Pangaro <pan@ATHENA.PANGARO.dialnet.symbolics.com>]

I need some advice on the state of things here. I am trying to avoid
work if the problem is known/obvious to others. And most of all, I am
hoping the answer won't be "The i/o port of the -20 is down....."

I am trying to switch modem service from ye olde 36-oh-oh to a 3620
bulkhead port (it's really a 3600 upgraded to a 3675, so the serial
lines plugs are the same gender, and the wiring for the cable is the
same, right?). All the software files are the same; I switch the modem
to the 3620 and I get a different behavior in the lights on the CDS
modem (and the dialnet software on the -20 says it can't find the
modem). The DIFFERENCE is that, when it all works on the 36-oh-oh, the
DTR and DSR lights on the modem are on steady (among others); on the
3620, when the Symbolics can't find the modem, the DTR is on but DSR is not
(in fact, DSR comes on briefly when you plug in the cable).

I have tried other cable configurations but have stopped short of
pulling out my black box and really thinking about it.  Same cable works
fine on 3600.

If it is the serial port on the -20, any ideas on what to check
internally? Thanks for the aid

--- a pathetic serial debugger