GE DigitalFlow DF868, Service Manual

Page: 40 / 68

Chapter 4. Parts Replacement
32 DigitalFlow™ Multipurpose Ultrasonic Liquid Flowmeter Service Manual
4.7 Installing the Printed Circuit Board
Whether the printed circuit board was removed for replacement or for one of the other procedures discussed in this
chapter, reinstallation of the printed circuit board is the final step in the process. Refer to Figure 8 on page 35 and
complete the following steps:
CAUTION! During this procedure, be very careful not to damage the vertical components along the top
edge of the printed circuit board (see Figure 9 on page 36). Severe or repeated bending of these
components will break their leads.
1. Position the printed circuit board within the electronics console with the top edge tilted forward. Insert the display
ribbon cable and keypad ribbon cable connectors into their sockets on the rear of the printed circuit board. See
Figure 8 on page 35 and Figure 9 on page 36 to identify the cables and sockets. Note that the keypad cable
connects to the upper socket and the display cable connects to the lower socket.
IMPORTANT:
The ribbon cables must be installed with the edges that were marked during removal oriented toward the
top of the printed circuit board.
2. Carefully position the printed circuit board up against the eight standoffs in the enclosure. Do not damage the
transformers and any installed option cards as they are maneuvered between the standoffs.
3. Loosely install the three long standoffs on the right side of the printed circuit board and the two short standoffs (or
screws) along the bottom edge of the printed circuit board.Then, install only the top and bottom short standoffs on
the left side of the printed circuit board.
4. Insert the free end of the green grounding strap between the printed circuit board and the middle standoff beneath
the left side of the board. Making sure to capture the grounding strap lug between the printed circuit board and the
standoff beneath it, install the remaining short standoff on the left side of the printed circuit board. Securely tighten
all eight standoffs and/or screws.
IMPORTANT:
Correctly installing the grounding strap may require some patience, but resist the temptation to place
the grounding strap on top of the printed circuit board.
5. Connect the twisted-pair backlight cable to socket
J2
on the left edge of the printed circuit board. This plug is
polarized so that it can only be installed in the proper orientation, with the black wire above the red wire.
6. Check for and remove any loose hardware that may have fallen into the electronics console during the maintenance
procedure.
7. Place the main shroud over the six upper standoffs on the printed circuit board. Making sure that the shroud is
oriented with the wiring diagram label upright, fasten the shroud to the standoffs with the six sets of screws and
washers.
8. Reconnect the power line wires and the PC board ground wire to terminal block
TB1
on the printed circuit board.
Plug all other electrical connectors into the appropriate sockets on the printed circuit board and option cards. See
Chapter 1,
Installation , of the Startup Guide for instructions on proper wiring of the Model DF868.
Note:
For an LVD compliant meter with the clear plastic shroud over the electrical connectors, there are standoffs in
the two mounting locations along the bottom edge of the printed circuit board. For meters not equipped with
this shroud, there are Phillips head screws in these two locations.