Chapter 4. Parts Replacement
28 DigitalFlow™ Multipurpose Ultrasonic Liquid Flowmeter Service Manual
4.2 Fuse Replacement
If it has been determined that the fuse in the Model DF868 requires replacement, complete the following steps:
WARNING! The main power to the Model DF868 must be disconnected before proceeding.
1. Open the cover on the electronics console. For LVD compliant units, remove the two mounting screws and lift the
clear plastic shroud out of the electronics console.
2. Locate the black plastic fuse holder that is mounted on the printed circuit board between the power terminal block
(TB1) and the RS232 terminal block. As shown in Figure 8 on page 35, the fuse holder extends below the main
aluminum shroud, and the fuse holder cap is located on the bottom of the fuse holder.
3. Using a small standard screwdriver, turn the fuse holder cap counterclockwise about 1/4 turn. The fuse holder cap,
with the captive fuse, will be ejected from the fuse holder.
4. Replace the defective fuse with a new one of the same rating and type. Use only 1-1/4” x 1/4” Slo-Blo fuses,
having a rating as indicated in Table 4 below and on the wiring diagram label.
5. Press the new fuse into the fuse holder cap and insert the fuse into the fuse holder. While applying a slight pressure
with the screwdriver, twist the fuse holder cap 1/4” turn clockwise.
6. For LVD compliant units, place the clear plastic shroud over the standoffs in the electronics console and secure it in
place with its two mounting screws. Close the cover on the electronics console.
The Model DF868 flowmeter may now be placed back into service. Reconnect the main power and resume taking
measurements.
Note: Be sure to record the fuse replacement in Appendix A, Service Record.
Table 4: Line Voltages & Fuse Ratings
Line Voltage Fuse Rating
100-120 VAC 1.0 A, Slo-Blo
220-240 VAC 0.5 A, Slo-Blo
12-28 VDC 3.0 A, Slo-Blo
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