Keithley 2700, Service Manual

Page: 78 / 174

3-6 Routine Maintenance
5. De-solder the blown CH21 or CH22 fuse as required, taking care not to damage the cir-
cuit board or spread solder flux around the board.
6. Install a new 3A, 250V fast-blow fuse, Keithley part number FU-107-1.
CAUTION Do not use a fuse with a higher current rating than specified or module
damage may occur.
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. Re-install the circuit board into the plastic housing, then close the top cover.
Replacing Model 7702 amps fuses
1. Turn off the power, and disconnect the power line and external connections from the
Model 7702.
2. Open the Model 7702 top cover.
3. Locate the amps fuses for CH41 and CH42 (see Figure 3-4 ).
4. Remove the circuit board from the bottom plastic housing by removing the two bottom
screws.
5. De-solder the blown CH41 or CH42 fuse as required, taking care not to damage the cir-
cuit board or spread solder flux around the board.
6. Install a new 3A, 250V fast-blow fuse, Keithley part number FU-107-1.
CAUTION Do not use a fuse with a higher current rating than specified or module
damage may occur.
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. Re-install the circuit board into the plastic housing, then close the top cover.