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SWTPC PR-40 Alphanumeric Printer Assembly Instructions
The SWTPC PR-40 Printer kit is a 5 X 7 dot matrix impact printer similar in
operation to the well known Centronics printers. It prints the 64 character upper
case ASCII set with 40 characters/line at a rate of 75 lines/minute on standard 3
7/8" wide rolls of adding machine paper. One complete line is printed at a time
from an internal forty character line buffer memory. Printing takes place either
on receipt of a carriage return or automatically whenever the line buffer memory
is filled.
The printer can accept character data as fast as one character per
microsecond or as slow as you wish to send it. The printer's seven parallel data
lines are TTL compatible and may be enabled by a single "data ready" control line
or by separate "data ready" and "data accepted" handshake control lines. This
universal approach makes the printer compatible with all computer and terminal
systems having an eight bit parallel interface; including of course the MITS 8800
and SWTPC 6800 computer systems just to mention a few.
The printer mechanism is attached to a black anodized aluminum chassis with
front trim panel which houses the unit's circuitry including its own 120/240 VAC
50 to 60 Hz power supply. This makes the printer's overall dimensions 9 5/8" wide
X 10 1/2" deep X 8 3/4" high.
Each unit is shipped with one ribbon and one roll of paper. Extra ribbons
are available from us while the standard adding machine paper may be purchased in
office supply stores.
Caution
When handling the print mechanism itself you must make absolutely sure not
to try to rotate the large plastic cylinder that moves the head. If this cylinder
is rotated so the top is turned toward the front of the printer, it may bend the
arm on the roller cam microswitch on the right hand side of the mechanism which
will not only damage the switch but will prevent the printer from operating.
Note
The print mechanism you receive may not have the paper roll holder
installed. If so, it along with the mounting hardware will probably be contained
within a separate bag. The paper roll holder is secured to the back of the print
mechanism with four screws.
Assembling the Unit
The electronics for the printer are constructed on two printed circuit
boards. The larger of the two is the PR-40A and contains all of the logic
necessary to drive the print mechanism. The smaller board is the PR-40B and
contains mostly power supply circuitry. When assembling the printer it is best to
first assemble the PR-40A board, then the PR-40B board, then complete the unit by
installing the chassis components and completing the wiring. The assembly
instructions have been written in this sequence.
Scanned and edited by Michael Holley Nov 25, 2005
Southwest Technical Products Corporation Document Circa 1976
