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During this interval, the processor generates tickle
pulses to periodically fire Q4, preventing the inverting-
input voltage from rising above the non-inverting input
voltage and repeating the reset cycle. If the tickle puls-
es stop for more than 150 mSec, the reset cycle is
repeated
7. EEPROM
The EEPROM stores customer data, including
mode names, button functions, and VIP settings. The
customer data can be altered only by enabling the
STORE function (grounding the MIC HI line), an auto-
matic function of the control unit programmer. Power
strobing minimizes EEPROM power consumptions.
Jumpers configure the EEPROM for the uses listed in
Table 6.
Table 6. EEPROM Jumper Table
Jumper
Use/Placement
JU1
Used for fixture options
JU2
IN for 630 1X Microprocessor
JU4
IN for 2K EEPROM;
OUT for 8K EEPROM (option W930)
JU5
IN for 8K EEPROM (option W930);
OUT for 2K EEPROM
8. Bus Transceiver
The serial bus transceiver consists of Q1, Q2, Q3,
and U4 (CA3140). Q1, Q2, and Q3 transmit data on the
bus, while U4 acts as a comparator to receive data from
the bus.
9. Vacuum-Fluorescent Voltage Converter
Voltage for the vacuum-fluorescent display is gener-
ated by a fixed-frequency, variable-duty-cycle driven,
flyback voltage converter. Q31 and Q32 form an emit-
ter-coupled astable multivibrator that runs at about 150
kHz. The square wave output from this circuit is inte-
grated by R71 and C39 to form a triangle that is applied
to the non-inverting input of half of U5.
During start up, the inverting input is biased at 3.7
volts by R66 and R67. Q23 is on while the non-inverting
input voltage is below 3.7 volts. This allows current to
flow to T1, building a magnetic field. When the triangle
wave exceeds 3.7 volts, Q23 turns off and the magnetic
field collapses, inducing negative current in T1.
This current flows through either CR13 or CR14,
charging C27 and C28. As the voltage on C28 increas-
es beyond -35 volts, CR13 begins to conduct, pulling
U5’s inverting input below 3.7 volts. This decreases the
cycle time that Q23 is on to the time needed to produce
-35 volts on C28. The -41 volt supply is not regulated,
but it tracks the -35 volt supply.
Similarly, the ac supply for the vacuum-fluorescent
filament is not regulated, but is controlled to within one
volt by an inductor on the display board.
10. Vehicle-Interface Ports (VIP)
The VIP outputs are driven by a serial-to-parallel
shift register. Output transistors (Q28, Q29, Q30) can
sink 300 mA current. Primarily, these transistors control
external relays. The relay is connected between the col-
lector and switched B+.
Each VIP input transistor (Q25, Q26, Q27) is con-
nected to a dedicated input port through transistors
used for input protection. These VIP inputs are con-
nected to ground with either normally-open or
normally-closed switches.
11. Power Supplies
Both the +5 and the +9.4 volt supplies are linear
regulators. The +9.4 supply is built with a discrete tran-
sistor (Q11). The regulation is provided by VR09. The
+5 volt supply is a 7805, three-terminal regulator IC.
12. Ignition Sense Circuits
Q7 senses the vehicle ignition’s state, disabling
transmit when the ignition is off. For negative-ground
systems, the orange lead is typically connected to the
fuse box (+12V). For more information, see the cable kit
section.
13. EEPROM Write-Protect Circuit
Q12, Q13, and associated circuitry guard against
inadvertently writing into the EEPROM. When MIC HI is
grounded, Q21 (normally on) is turned off. A hot-carrier
diode (CR24) ensures that Q21 turns off. CR24 is nor-
mally off so it does not interfere with the MIC HI line.
CR19 forces the system to be write-protected during
reset; this is especially crucial during system power-up.
14. Display Board
This board contains the main operator interface
points of the system, including the vacuum-fluorescent
display, the status indicator LEDs, and the user keypad.
15. Vacuum-Fluorescent Display
The vacuum-fluorescent (VF) display is an
11-digit, 14-segment display that needs three separate
voltages to operate: the cathode needs -35 volts to
accelerate electrons to the anode; the grid needs -40
volts to totally shut off current flow; the filament needs
3.8 volts ac at 80 mA. These voltages are obtained
from the VF up-converter on the controller board.
16. Vacuum-Fluorescent Display Driver
This IC (U101) receives ASCII data from the con-
troller board, decodes it into 14-segment display data,
and then scans the display with the data. Once properly
loaded into the driver, the displayed data is refreshed
without any further processor action. The display driver
is periodically reset by the actions of transistors Q118,
Q119, and Q110 that watch the clock line from the
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Troubleshooting
