TM 55-4920-429-13
4-1. General Instructions
Chapter 4
AVIM MAINTENANCE
SECTION I TROUBLESHOOTING
a. Troubleshooting procedures are provided in logic tree format. For each test paragraph, there is a
troubleshooting paragraph with a similar heading. For each failure to meet a test requirement, there is
a trouble symptom with a similar title. Use the schematic diagrams (FO-2 thru FO-4, fig. 1-2, 1-3, FO-6,
FO-7, fig. 1-4 and FO-8) and the wiring diagrams (FO-22) as aids in troubleshooting.
b. On wiring diagrams, wire connections to the moving contacts of rotary wafer switches stop at the
edge of the wafer. Physically, the moving contact is on the side of the wafer opposite the fixed contacts
and is centered between two fixed contacts.
c. During troubleshooting, observe the following precautions and procedures.
(1) Voltage measurements. The test set includes transistor and microcircuits. When measuring
voltages, use tape or plastic sleeving to insulate the test probe except for the extreme tip. A momentary
short can ruin a solid state device. Use the digital multimeter specified in para 4-2.
(2) Resistance Measurements. Perform resistance and continuity checks with electrical power off.
(3) When the test set is disconnected from external test connections, all grounds in the test set are
not at the same potential. Chassis ground is at receptacle pin J l-f. Dc common is at TB1-7. Ac neutral is
at TB1-3. Logic ground is at TB2-8. Analog ground is at TP2.
d For access to the rear of left-side front panel components, it may be necessary to remove the bot-
tom plate of the chassis assembly. (Refer to para 4- 17.)
e. Use a card extender, where necessary, for making test measurements at card receptacles.
4-2. Test Equipment Required.
TEST EQUIPMENT
TEST SPECIFICATION
Variable Ac Power Supply 400 Hz (2 ea)
Oscilloscope Dual Trace
Digital Multimeter
Decade Resistor
Dc Power Supply 0-36 Volt (2 ea)
Digital Multimeter
Gyro Test Aid
Card Extender
0 to 115 Vac 0.5%
0 to 6 Vac 0.5%
1 us to 500 ms/div
5 mV to 20V/div
Ac: 50mV to 150V 0.5%
Dc: 10mV to 50V 0.1%
1 ohm to 1.1 megohm 0.1%
±.5%
Ac: 50mV to 150V 0.5%
Dc: 10mV to 50V 0.1%
Locally fabricated (fig. 4-3)
Receptacle M55302/27-06 (60 pin)
to plug MS55302/26-02
4-1
