Panametrics DigitalFlow GM868, Руководство по обслуживанию

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DigitalFlow™ GM868 Service Manual 31
Chapter 4. Parts Replacement
4.3 Removing the Printed Circuit Board
All of the remaining maintenance procedures discussed in this chapter require removing the printed circuit board. To
accomplish this task, refer to Figure 8 on page 39 and Figure 9 on page 40 while completing the following tasks:
1. Remove the main power to the electronics console.
2. Open the electronics console. For LVD compliant units, remove the two mounting screws and lift the clear plastic
shroud out of the electronics console. Remove the six mounting screws and lift the main aluminum shroud out of
the electronics console.
3. Disconnect the main power leads and the PC board ground wire from terminal block TB1 on the printed circuit
board. Remove the electrical connectors from all installed option cards and terminal blocks. Disconnect the
twisted-pair display backlight cable from connector J2 on the left side of the printed circuit board.
4. Using a 3/8 in. nutdriver or open-end wrench, remove the three short standoffs along the left side of the main
circuit board and the three long standoffs along the right side of the main circuit board.
5. While supporting the printed circuit board, remove the two screws or standoffs along the bottom edge of the
printed circuit board.
Note: For an LVD compliant meter with the clear plastic shroud over the electrical connectors, there will be
standoffs in these two locations. For meters not equipped with this shroud, there will be Phillips head screws
in these two locations.
6. Carefully lift the printed circuit board out of the enclosure. Continue to support the printed circuit board, as the
keypad and display cables are still connected to the rear of the board.
7. Tilt the top of the printed circuit board forward, and mark the top edges of the two ribbon-cable connectors.
Then, remove these cables from their connectors on the rear of the board.
8. The printed circuit board is now free and may be removed to a clean work area.
If the printed circuit board is being replaced, proceed to the section on
Installing the Printed Circuit Board (page 35)
now. Otherwise, refer to the appropriate section for instructions on
Installing an Option Card (page 33), Replacing the
EPROM (below), or Replacing the LCD Display (page 34).
WARNING!
The main power to the Model GM868 must be disconnected before proceeding.
CAUTION!
During this procedure, be very careful not to damage the upright components
along the top edge of the printed circuit board (see Figure 9 on page 40). Severe or
repeated bending of these components will break their leads.