Keithley 2700, Service Manual

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4-18 Troubleshooting
No comm link error
A “No Comm Link” error indicates that the front panel processor has ceased communication
with the main processor, which is located on the motherboard. This error indicates that there
may be a problem with the cable connection from the front panel display or one of the main
processor ROMs may require reseating in its socket. Check to be sure there is a proper cable
connection from the front panel display. ROMs may be reseated as follows:
1. Turn off the power, and disconnect the line cord and all other test leads and cables from
the instrument.
2. Remove the case cover as outlined in Section 5.
3. Find the two firmware ROMs, U156 and U157, located on the motherboard. These are
the only ICs installed in sockets. (Refer to the component layout drawing at the end of
Section 6 for exact locations.)
4. Carefully push down on each ROM IC to make sure it is properly seated in its socket.
CAUTION Be careful not to push down excessively or you might crack the mother
board.
5. Connect the line cord, and turn on the power. If the problem persists, additional trouble-
shooting will be required.