Service manual

STP 11-25R13-SM-TG
3 - 72
INSPECT EQUIPMENT RACK GROUNDING SYSTEM
113-575-3048
Conditions: In a tactical or garrison environment, given equipment installed in a grounded equipment
rack with a central grounding system, multimeter with test leads, electronic equipment tool kit,
manufacturers' manuals, DA Form 2404, DA Form 2407, and DA Pam 738-750.
Standards: The standards are met when the inspection reveals a reading of not more than 5 ohms from
ground strap to test point and an infinite reading from AC plug to test point on the equipment rack.
Performance Measures Results
DANGER: IMPROPERLY GROUNDED RACKS OR EQUIPMENT COULD CAUSE AN
INDIVIDUAL TO BECOME GROUND, AND A DANGEROUS CURRENT WOULD PASS
THROUGH HIS OR HER BODY. A GROUNDING SYSTEM PROVIDES SOME
PROTECTION AGAINST VOLTAGE SURGES AND BUILT-UP STATIC CHARGES.
POOR GROUNDING CAN CAUSE HUM AND DISTORTION, AND IN SOME CASES,
TOTAL BREAKDOWN. DIGITAL EQUIPMENT IS PARTICULARLY SENSITIVE TO
POOR GROUNDING.
1. Turn OFF all equipment power switches in the rack. P F
2. Gain access to the internal chassis of an item of equipment mounted in the rack. P F
3. Check ground-to-ground resistance with a multimeter. P F
a. Turn ON multimeter and select the ohmmeter function. P F
b. Apply one test lead to the grounding strap on the rack. P F
c. Apply the other test lead to the ground test point on the item of equipment. P F
d. Check the meter reading for earth or floating ground, zero ohms. In all cases,
chassis ground should never exceed 5 ohms.
P F
4. Disconnect the lead from the grounding strap on the rack and apply the lead to one
side of the equipment AC plug. The other lead remains at the ground test point of the
equipment.
P F
5. Check resistance reading for infinity. P F
6. Perform performance measures 3 through 5 for all equipment in the rack. P F
7. Turn OFF the multimeter and remove the test leads from the equipment. P F
8. Annotate DA Form 2404 with the date and your initials if no problems exist, or record
uncorrected faults and parts required on the form.
P F
9. Initiate a DA Form 2407 for uncorrected faults and turn it into the supervisor for action. P F
Evaluation Guidance: Score the soldier a GO if all steps are passed (P). Score the soldier a NO-GO if
any step is failed (F). If the soldier fails any step, show what was done wrong and how to do it correctly.
Have the soldier practice until he can correctly perform the task.
References
Required Related
DA Pam 738-750 AR 385-10
Mfg Manuals NEC
TB 385-4