Fault Finding - NORTHROP GRUMMAN T6MC User Documentation

Fault Finding

WARNING
When the Power switch is set to the Standby position, dangerous voltage is still present in
the controller's internal power supply circuitry. To ensure safe working, the controller must
be isolated from the ac and dc input supplies.
Table 5-1 provides information on typical conditions that may be expected at selected points in the circuit
with the equipment functioning normally and under the test conditions indicated.
Table 5-1 T6MC Controller Circuitry - Typical Conditions
Function
Power Supply
Microphone VOGAD
Microphone amplifier
Line driver
Received signal from
T2
Received signal
Received signal
Sidetone output
Input to loudspeaker
amplifier IC4
Loudspeaker
amplifier IC4
Park Air T6MC Controller
Dangerous Voltage
Measurement
Point
TP1, TP2 and ac mains connected
TP3
IC3b pin 1 20 mV signal at microphone
input
IC2b pin 1 20 mV signal at microphone
input
IC8 pin 3 20 mV signal at microphone
input
Junction of R25 -13 dBm signal applied to
and R26 600 ohm line input (CN1 pins 1
and 2)
IC1a pin 7
More than 0 dBm or -13 dBm
signal applied to 600 ohm line
input (CN1 pins 1 and 2). RV2
set to maximum
Emitter of Tr5
More than 0 dBm or -13 dBm
signal applied to 600 ohm line
input (CN1 pins 1 and 2). RV2
set to maximum
IC2a pin 7 More than 0 dBm or -13 dBm
signal applied to 600 ohm line
input (CN1 pins 1 and 2)
Junction of R40 More than 0 dBm or -13 dBm
and the volume signal applied to 600 ohm line
control input (CN1 pins 1 and 2)
IC4 pin 2 More than 0 dBm or -13 dBm
signal applied to 600 ohm line
input (CN1 pins 1 and 2)
Page 5-4
Test Conditions
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Typical Reading
TP1 = +24 Vdc
TP2 = +12 Vdc
TP3 = +6 Vdc
1.4 V peak-to-peak
4.5 V peak-to-peak
3.5 V peak-to-peak
440 mV peak-to-peak
0 dBm, 5 V peak-to-peak
-13 dBm, 4.5 V peak-to-peak
0 dBm, 5 V peak-to-peak
-13 dBm, 4.5 V peak-to-peak
dc conditions: 6.4 V
0 dBm, 6 V peak-to-peak
-13 dBm, 1.5 V peak-to-peak
0 dBm, 100 mV peak-to-peak
-13 dBm, 400 mV peak-to-
peak
0 dBm, +6 Vdc
-13 dBm, +6 Vdc
Maintenance