National Instruments SCB-68 User Manual page 81

Fuse and Power
Caution NI is not liable for any device damage or personal injury resulting from improper
use of the SCB-68 and the DAQ device.
© National Instruments Corporation
One of the +5 V lines from the DAQ device (pin 8) is protected by an
800 mA fuse. Pin 14 is also +5 V, but it is not fuse-protected on the
SCB-68. Shorting pin 14 to ground blows the fuse, which is usually
socketed. If the SBC-68 does not work when you turn on the DAQ device,
first check the switch settings, then check both the 800 mA fuse on the
SCB-68 and the output fuse (if any) on the DAQ device. Before replacing
any fuses, check for short circuits from power to ground.
A 470 Ω series resistor (R21) filters the +5 V power on the SCB-68. As the
filtered +5 V is loaded, the voltage decreases. Pad R20 is in parallel with
R21, and you can install a resistor if needed. Shorting R20 bypasses the
filter while capacitively coupling DGND and AGND, and this
configuration is not recommended.
Refer to Figure 2-1, SCB-68 Printed Circuit
and other components on the SCB-68. A suitable replacement fuse for the
SCB-68 is made by Littelfuse and has part number 235 800.
C-1 SCB-68 Shielded Connector Block User Manual
C
Diagram, to locate the fuse