18 Apr
2011
18 Apr
'11
5:57 p.m.
Hi
I have been able to get my PDP 11/05 to print "hello world" by
entering a short program into the toggle switches. I can
simultaneously get the punch to print if I enable it. The text is
actually garbled (TE]HJVYRTD), but I assume I just have to make an
Does the teletype print correctly in local mode? Could it be a problem
with the receive mechanciam in the Model 33? Can you correctly read charactes from the Model 33
keyboard on the PDP11?
I have been trying to write a program that will do this using front
panel switches. I could use some help.
<snip>
I don't have one of these installed, as I have no base:
http://www.pdp8.net/asr33/pics/old_rdr_power.shtml
I believe that reader mod or no, I need to have power to the reader.
There was an 'official' Teletpye versio nwith
automatic reder control.
This detected 2 control chreactters using levers in the 'stunt box' under
the platen. These operated swithc contacts (there may well have been a
latching relay involved too) to control the trip coil circuit. This
version is not at all common (at least not over here).
<snip>
The first thing I would do is have the machine running
in Local mode with
the covers off and a piece of tape in the reader. Press down the armature
flap on top of the trip coil. If the reader now runs (and the tape
cotnents are printed out on the Model 33), then the reader and the
mechancial side of things ae all working properly, and any problems are
in the trip coil circuit (most likely)
no power for the reader.
I would invetigate thsi some more. What is the DC
resistance between the
2 connections that go to the reader circuit (with those wires
disconnected from the rest of the teletpye)? If inifinite, this does
suggest a relay contact.
I will check
Does anyhting happen if you apply 24V (or so)
between the 2 wires coming out of the machien from thsi device? If the
resistance drops to 'very low' then it really does sound like a relay.
Reconnect it, Apply 24V, and see if the reader runs now.
The PDP is sending -15V from mate-and-lock connector 4 and 6, for the
heck of it I tried this, quickly, but it had no effect.
The DEC connecotr has 6 pins used, 2 each for the
transmit currnet loop,
receive current loop and reader run relay. The last will drive a small
relay coil directly.
-15V?
Has this Model 33 ever been used on a PDP11? If so,
it's likely to be
vertsion of the normal DEC modification and you can just connct up the
relay coil wires to the 2 remaining pins on the mate-n-lock.
TTY "lineage unknown"