| +Home | Museum | Wanted | Specs | Back | Next |
Wang LOCI Printer
Updated 2/24/2002
Exhibited here is a Wang LOCI Printer. The LOCI printer is a peripheral device designed to connect to a properly-optioned Wang LOCI-2 calculator, providing hard-copy output capabilities for the calculator.The Model/Serial Tag on the LOCI Printer
The LOCI Printer exhibited here was
manufactured in the late part of 1966, based on date code information
on some of the components in the machine. It is intended to be connected
to a LOCI-2 calculator equipped with the "Option D" Input/Output interface.
The I/O interface for the LOCI-2 calculator occupies an option slot in the
calculator that provides a generalized Input/Output bus structure for connection
of peripheral devices.
Inside the LOCI Printer
The LOCI Printer is built in a very
modular fashion, with three main assemblies making up the device.
The 'MODUPRINT' Printer Module
The first component is the printer module.
The printer is contained in a drawer that pulls out of the main
cabinet, to allow paper and ribbon changes. At the back of the printer
module is a circuit board edge connector that mates with a socket inside
the main chassis. This design assures that when the drawer is pulled out,
power is removed from the printer module.
ID Tag on the Printer Module
he printer module is a Model
B3-9 printer, manufactured for Wang by a company called
Practical Automation, Inc.,
located (at the time) in Shelton, Connecticut. This company is still in
business making specialized printing devices, however, over the years, the
company has changed ownership a number of times. A query sent via EMail to the
company resulted in a kind response back saying that the information on this
old printer has long-since been lost through ownership changes and moves.
It appears that the MODUPRINT modular printer concept was developed by
the Presin Co, Inc., of Bridgeport, Connecticut. The museum has found
an old Technical Data Sheet from Presin describing their new
MODUPRINT Data Printers in
Preliminary Bulletin 602
likely published sometime in 1966. Somewhere along the line, it appears
that Presin Co., Inc. changed its name to Practical Automation, Inc.,
although it isn't known exactly when this change occurred.
The Wang LOCI Service Manual references the "Presin Printer" as an option
for the LOCI 2 calculator, indicating that at the time this document was
published, which was sometime in 1965, that the company was still
called "Presin Co., Inc.".
The mechanism by which the machine
prints is quite interesting. For a long time, I couldn't tell how this
device printed, but thanks to a kind visitor to the museum, Mr. Charles
Levinski, the mystery is solved. Mr. Levinski is the sales/product
manager for a company named "HECON". This
company is a long-time manufacturer of specialized ticket and document
printers (among other equipment), and a competitor of Practical Automation
in the ticket printer market.
The technology is called "Modular
Printing". The principle is quite simple. Each column to be printed is
served by a print module. Each module contains a wheel that has raised
characters (digits, symbols) around its circumference. The wheel also has
gear-like teeth that are engaged via an escapement mechanism to allow the
wheel to be turned a character at a time when activated by a small solenoid.
Along with each wheel there is a set of contacts that encode the position
of the wheel, to allow the driving electronics to know when the print wheel
is in the proper position for the selected digit or symbol to print.
As many of these modules are assembled together for the number of columns
needed to be printed. In the case of the LOCI Printer, there
are twelve modules, one for each column. The modules are arranged so
that a sizable solenoid can push the print wheels up against the paper (with
a ribbon interposed between the embossed symbols on the print wheel and the
paper) so that the symbols are printed. The act of the large solenoid releasing
causes the ribbon and paper to advance.
The modular printer in the LOCI Printer can print up to 11 columns of
digits (one position for the floating decimal, and ten digit positions),
and one column of special characters (sign). The print solenoid is quite
powerful, and emits a fairly loud thunk when the actual printing occurs.
The individual module print-wheel advance solenoids are quite quiet, emitting
only a slight clicking noise as they advance the print wheels. The paper exits
the printer module through a slot at the front of the printer.
According to the tag on the printer, it runs from a 24 Volt DC power
supply, and requires up to 1.6 Amps of current.
The Logic Card-Cage of the LOCI Printer
The next major component of the LOCI
printer is the printer logic chassis. The all-transistor logic that
controls the printer is located in a chassis of its own down the
left side of the printer chassis. A total of fourteen small circuit boards
make up the logic that drives the printer and provides interfacing to the
I/O interface in the LOCI calculator.
Some of the LOCI Printer's Logic Circuit Boards
Some of these circuit boards appear to
be a form of standard logic modules, such as one card which appears to
have six three-input logic gates, and another that has eight two-input gates.
These standardized logic modules are based on Wang's "Logi-Bloc" products,
used in Wang's custom process-control and numerical-control system designs.
The circuit boards are made of fiberglass, and have traces on both sides of
the board, with plated through holes. Each board has thirty edge-connector
contacts for bringing power and logic signals into and out of the board.
The boards plug into a hand-wired backplane using the tried and true
AMP square pin and clip interconnect technology, used extensively in Wang's
early electronic devices. As with the LOCI-2 itself, the majority of the
transistors in the logic are RCA-made 2N404 Germanium devices. One circuit
board has two 2N1540 power transistors which are used to drive the print and
paper advance solenoid.
The Backplane and Power Supply Wiring
The last section of the printer
system is the power supply, made up of two small power
transformers, diode rectifiers, and filtering capacitors. The voltage
supplies do not appear to be regulated, rather, they are simply set
in-situ to deliver the proper voltages, using a tapped wire-wound power
resistor. The power supply generates the supply voltages for the logic
circuitry, as well as the 24 volt supply used by the printer module.
Operation of the printer is
as simple as can be. Simply plug the printer into AC power, plug the cable
between the back of the printer and the LOCI-2's port labeled "OUTPUT",
and turn on the power to the printer. The printer's power switch is located
on the front panel of the printer, accompanied by a yellow-jeweled pilot lamp
that lights to indicate when the power is turned on. The rear panel of the
printer contains a fuse holder, the power cord, and a single 50-pin female
Centronics-style connector to plug in the cable to connect the printer to the
calculator.
To advance the paper, it can
simply be pulled out manually, or the printer can be commanded to do so from
the calculator, by pressing the [CAR'GE RET] key on the Option D-equipped
LOCI-2 keyboard (or through a program via operation code 75). To print the
content of the LOCI-2's display, the [WRITE] (operation code 11) key is
pressed. The printer prints about one line per second. The calculator waits
for the printer to complete its cycle before proceeding.
