Appendix B. Optional Enclosures
46 DigitalFlow™ Multipurpose Ultrasonic Liquid Flowmeter Service Manual
B.7 Rack Mount Printed Circuit Board Replacement
If troubleshooting procedures have indicated a defective printed circuit board, follow the instructions in this section to
replace the defective board with a new one.
B.7.1 Circuit Board Removal
Refer to Figure 11 on page 50 and complete the following steps:
1. After disconnecting the main power to the meter, remove the top panel from the enclosure by removing the four
screws indicated.
WARNING! The main power to the Model DF868 must be disconnected before proceeding.
2. Disconnect all external option card connectors at the rear panel of the meter. Then, remove all installed option
cards from the printed circuit board, as described earlier in this chapter.
3. Disconnect the main POWER LEADS from the screw terminals at the rear of the printed circuit board. Make a sketch
of the terminal block and the locations of the black, white and green power leads to assist in reinstallation on the
new circuit board.
4. Remove the RS232, ANALOG OUT and TRANSDUCER connectors from the printed circuit board. Use a marker to
identify pin #1 on the right side (keypad side) of these connectors.
Note: These connectors should be pulled straight up and off the printed circuit board. DO NOT remove the leads
from the screw terminals.
5. Remove the flat KEYPAD CABLE connector from terminal J50 near the front of the printed circuit board. Mark pin #1
of the cable connector, which is located nearer the rear of the enclosure.
6. Disconnect the twisted-pair DISPLAY BACKLIGHT cable from connector J2 beneath the left side of the printed circuit
board. Although this connector is polarized, it will help to note that the red wire is closer to the rear of the
enclosure.
7. Remove the flat LCD DISPLAY CABLE connector from terminal J52 near the option card sockets. Mark pin #1 of the
cable connector, which is located nearer the front of the enclosure.
8. Using a slotted screwdriver, remove the three mounting screws along each side of the printed circuit board.
Carefully lift the printed circuit board out of the enclosure.
Proceed to the next section for instructions on installing the new printed circuit board.
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