Section 7: Maintenance
Series 3700A System Switch/Multimeter Reference Manual
7-2
3700AS-901-01 Rev. D/June 2018
Fuse location
Rating
Keithley Instruments part
number
1. Analog backplane fuse
250 V, 3 A fast blow 5 x 20mm
FU-99-1
2. Instrument fuse
250 V / 1.25 A slow blow 5 x 20mm
FU-106-1.25
To replace a fuse:
1. Power off the instrument and remove the line cord.
2. Using a flat-tip screwdriver, disengage the fuse holder by rotating it counter-clockwise.
3. Pull out the fuse holder and replace the fuse with the correct type (see table).
4. Reinstall the fuse holder.
If a fuse continues to become damaged, a circuit malfunction exists and must be corrected. Return
the instrument to Keithley Instruments for repair.
AMPS analog backplane fuse replacement
Make sure the instrument is disconnected from the power line and other equipment before
replacing the AMPS fuse.
Do not use a fuse with a higher current rating than specified or instrument damage may
occur. If the instrument repeatedly blows fuses, locate and correct the cause of the trouble
before replacing the fuse.
Model 3721 card supports both AC and DC current measurements. Refer to the
Series 3700A Switching and Control Cards Reference Manual
. The Model 3721 card has
replaceable fuses. For replacement information, refer to the "Model 3721: AMPS channels fuse
replacement" section in the
Series 3700A Switching and Control Cards Reference Manual
.
To replace the analog backplane fuse:
1. Turn off the power and disconnect the power line and connections.
2. From the rear panel, gently push in the AMPS fuse holder with a flat blade screwdriver and rotate
the fuse holder one-quarter turn counterclockwise.
3. Remove the fuse and replace it with the same type (3 A, 250 V, fast-blow, 5 × 20 mm). The
Keithley Instruments part number is FU-99-1.
4. Install the new fuse by reversing the procedure above.
