Keithley 2750, Service Manual

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3-6 Routine Maintenance Model 2750 Multimeter/Switch System Service Manual
5. De-solder the blown CH21 or CH22 fuse as required, taking care not to damage the
circuit board or spread solder flux around the board.
CAUTION Do not use a fuse with a higher current rating than specified or module
damage may occur.
6. Install a new 3A, 250V fast-blow fuse, Keithley part number FU-107-1.
7. Solder the new fuse in place using organic (OA based) flux solder, again taking
care not to damage the circuit board or spread solder flux around the board.
8. Carefully clean the repaired area of the circuit board with a foam tipped swab or
brush dipped in pure water, then blow dry the board with dry nitrogen gas. Allow
the board to dry for several hours in a 50°C low-humidity environment before use.
9. Reinstall the circuit board into the plastic housing, then close the top cover.
Replacing non-volatile RAM battery
The Model 2750 has a three-year lithium battery for non-volatile RAM. Use the procedure
below to replace the battery, if required. Refer to the disassembly procedures in
Section 5
and the parts list and component layout drawings at the end of Section 6 for more informa-
tion.
WARNING There is a danger of explosion if the battery is incorrectly replaced.
Replace only with the same or equivalent type recommended by the manu-
facturer. Dispose of used batteries according to federal, state, and local
laws.
The following procedure is intended only for qualified service personnel.
Do not perform this procedure unless you are qualified to do so.
Disconnect the line cord and all connecting wires from the Model 2750
before removing the top cover.