TM 5-3895-374-24-2
Blending Controller Fails to Respond
NOTE
The system power supply provides four fused 24 volt DC outputs from a single
short circuit proof 24 volt DC supply. A short on any one output may NOT cause
its fuse to blow but may cause the main 24 volt DC supply to be pulled to zero, or
nearly zero volts DC. The other three fused outputs win then also Indicate 0 volts.
The test procedure removes al four fuses and reinstalls them one at a time. If no
fault is present, the 24 volt DC will appear as the fuse is reinstalled; otherwise a
fault is present and must be corrected. Perform the following procedures:
Inspect all sensor cables and connections.
Remove the V1, V2, V3 and V4 fuses and check for continuity (note fuses V2 and V4 are not used internally or externally).
1.
If the fuses are good, replace the VI fuse and measure the voltage from V1 to COM.
2.
If this voltage is less than 22 vdc, a fault external to the computer and in equipment connected to V1 is indicated.
Disconnect the field cable to TB13 terminal 3 in the belt scale amplifier junction box and again measure V1.
Reconnect the field cable.
3.
If V1 is less than 22 vdc a fault in the cable is indicated.
4.
If V1 is 22 to 26 vdc, replace the scale load cell amplifier and re-calibrate the belt scale.
5.
When V1 is 22 to 26 vdc, replace the V3 fuse and measure the voltage from V3 to COM.
6.
If this voltage is less than 22 vdc, a fault external to the computer and in equipment connected to V3 is indicated.
Disconnect the jumper on TB14 between terminal 4 and terminal 5 in the asphalt meter J-box and again measure
V3. Reconnect the jumper wire.
7.
If V3 is 22 to 26 vdc, replace the tree wire asphalt rate pickup probe in this J-box. The asphalt meter calibration
may not change if the correct replacement is properly installed. Replace the pickup wheel if its rubber outer ring
shows any signs of physical damage.
8.
If V3 is less than 22 vdc, disconnect the field cable from TB14 terminal 5 in the asphalt meter J-box and measure
V3. Reconnect the field cable to terminal 5.
9.
If V3 is less than 22 volts, a fault in the field cable is indicated.
10.
If V3 is 22 to 26 vdc, replace the AC temperature probe amplifier and recalibrate the probe according to
procedures in the operators manual.
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