3-1
SECTION III
MICROPROCESSOR INSTALLATION
NOTE
It is necessary to perform the procedures in
this section ONLY if a field software upgrade
is performed.
3-1. GENERAL.
Three microprocessors are necessary for Vision®
warning system operation. They MUST be changed
as a set. Each microprocessor in a set has a specific
function, and MUST be installed in the correct circuit
board.
The microprocessor’s part number denotes its
function. The fourth and fifth character in the part
number indicates its function as follows: CH =
Control Head, BB = Interface/Relay Unit, BC = Bar
Controller. Ensure that the correct microprocessor is
installed in its corresponding circuit board.
3-2. INSTALLATION.
CAUTION
The CMOS microprocessors and the Vision’s
circuitry can be destroyed, or damaged, by
static discharge. Observe anti-static proce-
dures when installing or handling CMOS
devices or any of the Vision’s circuit boards.
A.
Control Head.
1.
Disassemble the Vision control head as
described in the Service and Maintenance section of
the Vision Installation and Maintenance Instructions
(Part No. 255247).
2.
Gently pry the microprocessor (IC4)
out of its socket with a small screwdriver.
3.
See figure 3-1. Insert the new micro-
processor IC (“CH” in the part number) in the empty
socket. Ensure that the notch on the new micropro-
cessor IC is facing the same direction as the old one
(away from the modular jack) and that all IC pins are
properly inserted in the socket—not bent under.
4.
Reassemble the control head.
B.
Interface/Relay Unit.
1.
Disassemble the Vision Interface/
Relay Unit as described in the Service and Mainte-
nance section of the Vision Installation and Mainte-
nance Instructions (Part No. 255247).
2.
Gently pry the microprocessor (IC2)
out of its socket with a small screwdriver.
3.
See figure 3-2. Insert the new micro-
processor IC (“BB” in the part number) in the empty
socket. Ensure that the notch on the new micropro-
cessor IC is facing the same direction as the old one
(away from the relays) and that all IC pins are
properly inserted in the socket—not bent under.
4.
Reassemble the Interface/Relay Unit.
C.
Bar Controller.
1.
Disassemble the Vision lightbar as
described in the Service and Maintenance section of
the Vision Installation and Maintenance Instructions
(Part No. 255247).
2.
Locate the bar control circuit board.
3.
Remove the screws which retain the
circuit board.
4.
Disconnect the modular connector.
Carefully lift the circuit board just enough to discon-
nect the 14-pin connector (J9) which connects the bar
control circuit board to the lamp driver circuit board.
The microprocessor IC should now be accessible.
5.
Gently pry the microprocessor (IC10)
out of its socket with a small screwdriver.
Figure 3-1. Control Head Microprocessor.
Summary of Contents for VISION
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