Scale-Tronix 5002 - Page 27

EPT-1014LW2 printer and EPT-R1002 interface:
“ON” jumpers: SW3, SW4, SW5, SW7, SW8, SW9,
SW10
"OFF" (or removed) jumpers: SW1, SWW2, SWB,
SW11. SW12
EPT-201452L printer and EPT-R2002 interface;
“ON" jumpers: SW2, SW4, SW7, SW8, SW10
“OFF” (or removed) jumpers: SW1, SW3, SW5, SWE,
SW9、 SW11, SW12
Contact the factory service department if additional
help regarding the proper jumper positions is needed.
The interface board is considered a non-repairable
assembly, although some limited information may be
available from the factory service department. A
schematic is included in this manual,
4.53 PRINTER CONTROLLER BOARD TYPES
23PRTRO2/23PRTRO3/23PRTRO4
An additional printer component is the printer
controller board, The printer controller board is used
to link the scale's instrument board and the printer
interface board. It also acts like a switch and voltage
regulator to provide a regulated source of +5 volts DC
to operate the printer and printer interface board while
printing. The voltage is removed when the printing
stops to conserve battery life. Schematics of these
controllers are included for the following fechnical
descriptions.
4.54 PRINTER CONTROLLER VOLTAGE
REGULATION
The primary purpose of the printer controller
board is to provide a source of switched, regulated +5
volts DC. Integrated circuit U201 is a 5 volt regulator
which works in conjunction with transistor Q201. The
output voltage is applied to U201's feedback pin
labeled "FB". U201's output pin ("DRV") will drive
Q201's base through biasing resistors R201 and
R202 in order to maintain a precise +5 volts out.
Unregulated battery voltage is applied through
connector J201 and regulated +5 volts is available at
J204.
Transistors Q202 and Q203 are used to switch the
voltage regulation "on" only when the printer is needed
so as to conserve battery life. Q203 receives an “on”
signal from the instrument board's "RTS" line through
biasing resistors R210 and R211. Q203 then turns on
Q202 through biasing resistors R203 and R204.
When Q202 is switched on it allows U201 to drive
Q201.
Capacitors C201 and C202 serve as input and output
filters respectively. Light emitting diode LED20% and
its current limiting resistor R209 are provided as a
power-on indicator to help with trouble-shooting.
Schottky diode BAT42/BATB5 is added for reverse
battery protection.
NOTE: REVERSE BATTERY MODIFICATION
Some early versions of the 23PRTR02 8 23PRTR03
printer controller board did not contain sufficient
protection against reverse battery insertion. Capacitor
C201 should be changed from a 47uF/16V tantalum to
а 47uF/35V aluminum electrolytic. A type BAT42 or
BAT85 schotiky diode should be added to the base
and collector of ©201, with the cathode of the
BAT42/BAT85 connected to the base of Q201 (see
schematic). The 23PRTRO4 board has this diode,
GR203, already added.
4.55 CONTROL SIGNAL SUMMATION
The printer interface board provides some
control signals to tell the scale’s instrument board
when the printer is ready to accept data. These lines
connect to the controller board on J203, pins 2, 3, 4,
and are labeled "RTS" (ready-to-send), "DTR" (data
terminal ready), and "ERROR". For simplicity these
are logically summed together to produce a single
ready signal.
On the 23PRTRO2 controller board this is done by
папа gate U202 and the result appears on J202, pin
2. Current limiting resistor R212 is included to
interface to the scale's instrument board "CTS" (clear-
to-send) line. Note: When interfacing to a 23005R02
instrument board, diode CR204, а 14914 small signal
diode, should be added in parallel to resistor R212 as
shown on the schematic.
The 23PRTRO3/23PRTRO4 assemblies are similar,
except U202(B), a 1-of-4 decoder gate, is used to
logically sum the various control lines together.
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