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4.2 ROM REPLACEMENT
If a software update is required, it may be performed by replacing the operating system ROM located
on the Main Board. When replacing the ROM, all user waypoints/settings will be lost. The message
“Stored Data Lost” will be displayed. The unit must then be attached to an antenna, allowed to search
the sky and collect new almanac data before it will be usable again. This process may take 20-30 min-
utes. (A user data card is available to save user waypoints/settings prior to replacing the ROM. Refer
to page 5 of this manual for more information.)
1. Turn the GPS 155 is turned off.
2. Remove the bottom cover as described in Section 3.1.
3. Locate the ROM in the middle of the Main Board, as shown in figure 6.
NOTE: The ROM removal tool (P/N T00-00007-00) is contoured for insertion into either of the two
extraction cavities on the chip carrier socket. Remove the chip by inserting the extraction tool with the
correct angle (see figure 8) and pivoting the tool on its heel against the socket.
4. ROM Extraction Procedure:
a. Orient the socket and tool as shown in figure 9.
CAUTION: Do not attempt to completely extract chip from chip carrier socket on the first extraction. Lift
from one side until the corner is above the socket, then repeat the procedure on the opposite corner.
b. Insert the extraction tool into the socket so that the front angle of the tool is perpendicular to the chip
carrier. NOTE: Insertion of the tool with an incorrect angle will result in damage to the chip carrier
socket. The incorrect angle will bottom under the standoff rather than the bottom of the chip.
c. Lower the extraction tool into the extraction cavity until it bottoms.
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Figure 8
ROM Tool Insertion