Keithley 2701, Service Manual

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Model 2701 Service Manual Routine Maintenance 3-5
Replacing Model 7700 plug-in module amps fuses
WARNING The information in this section is intended only for qualified service per-
sonnel. Do not perform these procedures unless you are qualified to do so.
Make sure that all plug-in module connections are de-energized and dis-
connected before replacing module amps fuses.
1. Turn off the power and disconnect the power line and external connections from the
Model 7700.
2. Open the Model 7700 top cover.
3. Locate the amps fuses for CH21 and CH22 (see Figure 3-3 ).
4. Remove the circuit board from the bottom plastic housing by removing the two bottom
screws.
Figure 3-3
Model 7700 amps fuses
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.
H L H L
AMPS
H L H L H L H L H L H L
LO
CH21 CH22 CH11 CH12 CH13 CH14 CH15 CH16
H L H L H L H L
CH17 CH18 CH19 CH20
SENSE
(OHMS, 4 WIRE)
INPUT
(V, 2 WIRE)
H L H L H L H L
CH7 CH8 CH9 CH10
CH22 Fuse CH21 Fuse
Model 7700
H L H L H L H L
H L H L H L H L
INPUT SENSE CH1
CH2 CH3
CH4 CH5
CH6