Scale-Tronix 5002 - Page 28

Current limiting resistor R207 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, a 1N914 small sígnal
diode, should be added in parallel to resistor R207 as
shown on the schematic.
Resistor R205 is provided as a “pull-up” for the
printer interface board's reset line C/RESETY, located
at pin 6 of J203.
4.56 PRINT DATA SIGNAL
The data to be printed is applied to J202, pin
5, the TXD (transmit data) line from the scale's
instrument board. The data signal receives no
additional processing and is applied directly to the
printer interface board's "RXD" line (received data) at
3203, pin 1.
4.57 MANUAL PAPER ADVANCE, TYPE
23PRTR02 ONLY
Some additional circuitry is included to
provide a manual paper advance for loading the
paper roll. The manual paper advance must first
apply power to the printer interface board, then set
the "PF" line (paper feed). The “/PF” line must be
brought to ground to perform the paper advance.
Pressing switch S201 turns on transistor Q202
through diode CR201. The switch also turns off
transistor Q204 (through diode CR202) which is
normally biased "on" by resistor R206. Capacitor
C203 begins charging through resistor R207, causing
voltage to appear across R207 and the printer
interface board's "/PF" line (paper feed), located on
pin 5 of J203. As charging completes the voltage
across R207 drops until the PF" line signal becomes
sufficiently low to start the paper advance function.
4.58 MANUAL PAPER ADVANCE, TYPES
23PRTRO3/23PRTRO4 ONLY
The manual paper advance on the
23PRTRO3/23PRTRO4 provides the same type of
function as described above, but is accomplished in
a slightly different manner. Rather than employ a
resistor-capacitor time constant to generate a delay
when first turned on, logic gating is employed.
The "RTS" line from the printer interface board, pin 2
of J203, is used as an input to U202(A), a 1-of-4
decoder. The paper advance switch, S201, is also
used as an input to U202(A), through diode CR202.
Resistor R206 biases U202(A)'s inputs so they are
normally “high” ("pull-up” resistor), When S201 is
pressed the +5 volt power supply will be switched on
immediately through diode CR201 turning on Q202.
After a short period of time (about 1-2 seconds) the
printer interface board is ready; its "RTS" line (pin 2 of
4203) will go “low”. This will enable pin 15 of U202(A).
The output of U202(A), pin 12, will pull the "/PE" line
(paper feed), located on pin 5 of J203, "low", starting
the printer’s paper advance.
4.60 TROUBLE SHOOTING PROCEDURES
The following simplified trouble shooting
procedures are recommended for identifying defective
system components. Certain corrective measures are
provided. More complicated servicing should only be
performed by the factory or authorized service
facilities. Most problems can be solved on the
telephone. Problems reguiring factory service are
usually handled quickly and the scale is on its way
back within 24 hours. Call first to discuss the problem.
4.60.1 DISPLAY DOES NOT ILLUMINATE
Check that known good cells are properly
installed in the battery holder, or in the case of AC
operated scales, that the readout is plugged-in. On
AC powered readouts check if the internal power-on
し LE.D. is illuminated; if not check the line fuse(s).
Check that the battery connector is properly connected
to “J1 POWER” on the instrument circuit board.
Check that the cable between the display board and
instrument board is connected. Check that the
membrane keyboard is connected to the display board.
Measurements of the D.C. supply voltages can be
made with a DVM or analog multimeter.
4.60.2: WEIGHT READING NOT ACCURATE
This can commonly be caused by a
mechanical obstruction of the weighing platform,
Check that the platform is not touching some foreign
object so that it is restricted in its downward
movement. Also check that the connecting cable is
firmly plugged into the instrument circuit board
(marked "44 LOAD CELL"). On those scales with
26 5002, 5102, 5602, 8002, 6102, 6202, 6502, 6702