ASR33 questions - test-drb@ccmp.vtda.org

31 Aug 2002

On Aug 31, 18:59, Erik S. Klein wrote:
...
  I just received one of William's ASR33s and it
appears to be in good
 working order.  I am not at all familiar with these machines so I have a
 few questions about their operation and interfacing.
 First off, when I power on this unit the "main" motor doesn't run.  It
 turns when moved manually, but it won't move by itself.  Depending on
 the motor position at power-up (I think) I sometimes hear what sounds
 like a warning buzzer.  Is there something I'm doing wrong?  How would I
 run this machine in "local" mode? 
Sounds vaguely similar to a problem I have (occasionally) with mine.
 Sometimes the motor noise starts to rise and fall slightly, as if the
motor is struggling; eventually it blows the fuse.  In my case, I suspect
the problem is something binding (needing adjustment) and/or needing
correct lubrication.  There are lots of parts that need lubrication, and
it's definitely NOT a case of oiling or greasing everything in sight!
There should be a knob on the front right.  Turn left for online, centre
off, right for local.
...
  Once I figure out that this machine is working (I
assume the problems
 are mine and not the machines) I'd like to hook it up to my Altair
 (which is now running great thanks to Dwight!).  How would I go about
 doing this?  I'm guessing I'll need some sort of box to interface
 between the TTY and RS232, but I haven't yet found any information on
 that.  Can anyone point me to an article, website or some other source
 of information on this? 
You'll need a couple of RS232-to-20mA current loop converter circuits, one
for the Tx line and one for Rx.  Usually a small power supply, a couple of
opto-isolators, and just a few other components.
...
  What am I missing?  Is there anything else I should
know? 
Probably ;-)   But I'd get the machine working in local mode before you
start worring about interfacing it.  David Gesswein's excellent site at
www.pdp8.net has the ASR33 manuals in the document archive.
--
Pete                                            Peter Turnbull
                                                Network Manager
                                                University of York