TM 5-3810-306-34
TABLE 3-1. DIRECT AND GENERAL SUPPORT TROUBLESHOOTING (CONTD)
Malfunction
Test or Inspection
Corrective Action
84.
MALFUNCTION OF ANTI-TWO-BLOCK SYSTEM
Step 1. Check if jumper/dummy plug in receptacle at boom nose is plugged in. If OK go to Step 2.
a.
Plug in jumper/dummy plug.
Step 2. Remove jumper/dummy plug from receptacle at boom nose and check ohm reading between terminals 23 and 24
of Anti-Two Block switch. (Refer to page 3-69.) Readings should be:
Safe condition = 0 ohm
Block-to-Block = greater than 1 megaohm
If OK go to Step 3.
Step 3. Disconnect wire from CPU terminal board, terminal block X1, Pin 35. Check ohm reading between Pin 1 and Pin
6 of receptacle at boom nose. (Refer to page 3-70.) Readings should be:
Anti-Two-Block Switch Closed = 0 ohm
Anti-Two-Block Switch Open = greater than 1 megaohm
If OK go to Step 4.
a.
Fault in wiring cable from Anti-Two-Block switch to junction box at boom nose. Repair as necessary.
b.
Short circuit in length cable. Repair as necessary.
Step 4. Reconnect jumper/dummy plug in receptacle at boom nose. Disconnect length cable from slip rings terminals 17
and 18 in cable reel. (Refer to page 3-71.) Check ohm reading between center and shield of length cable.
Readings should be:
Anti-Two-Block Switch Closed = 4700 ohms + 500 ohms
Anti-Two-Block Switch Open = greater than 1 megaohm
If OK go to Step 5.
a.
Faulty wiring between receptacle at boom nose and cable r eel. Repair as necessary.
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