STRAIN-SENSITIVE CABLE FENCE SENSOR FAILURE

TM 5-6350-275-24&P

Table 3-9. Sensors DS Maintenance Troubleshooting - Continued

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

12. STRAIN-SENSITIVE CABLE FENCE SENSOR FAILURE (Figure 3-21)

NOTE

Refer to the SAIG for details on the strain-sensitive cable fence sensor.

Step 1. Check to ensure 20 vac stepdown transformer (2) is firmly connected to a 120 vac power source.

If assembly sensor is still in alarm status, go to step 2.

Step 2. Open door (4) on processor assembly (1) and check coaxial cables (5) to ensure that cables are connected

and locked onto connector.

If cable(s) have come loose from connector, reconnect and verify system is not in alarm status.

If in alarm status, go to step 3.

Step 3. Set multimeter to read VAC. Place leads across TB2 pins 9 and 10 to read 20 VAC.

If reading less than 18 VAC, replace 115/20 VAC step-down transformer.

If system is still in alarm, replace processor assembly PWA (Para. 3-125).

If system is still in alarm, go to step 5.

Step 4. For DC powered sensors, set multimeter to read vdc. Place negative lead on TB2 pin 8 and positive lead

on TB2 pin 7. The multimeter should read +12 vdc.

If reading is less than 10 vdc, replace power source.

If system is still in alarm, replace processor assembly PWA (Para. 3-125)

If system is still in alarm, go to step 5.

Step 5. Disconnect coaxial cable between processor and problem zone. For zones with cables over 400 feet, use

only an analog meter. Set meter to read ohms and measure cable resistance between center conductor and shield.

The meter should read 1 Megohm 100 kilohm resistance.

If cable is shorted or open, problem is in line between processor and terminator.

If reading is outside range 1 Megohm

100 kilohm, problem is in terminator or junction splice assembly or

assemblies. Go to step 6.

Step 6. Visually inspect terminator and each splice junction (6).

If no faults are visible, replace terminator and retest (Para. 3-126).

If necessary, replace splice devices (Para. 3-126) until you get a good meter reading between center conductor

and shield of cable at processor.

3-68