NORTHROP GRUMMAN T6MC, User Documentation

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Park Air T6MC Controller Page 5-4 Maintenance
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Fault Finding
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
Measurement
Point
Test Conditions Typical Reading
Power Supply TP1, TP2 and
TP3 ac mains connected TP1 = +24 Vdc
TP2 = +12 Vdc
TP3 = +6 Vdc
Microphone VOGAD IC3b pin 1 20 mV signal at microphone
input 1.4 V peak-to-peak
Microphone amplifier IC2b pin 1 20 mV signal at microphone
input 4.5 V peak-to-peak
Line driver IC8 pin 3 20 mV signal at microphone
input 3.5 V peak-to-peak
Received signal from
T2 Junction of R25
and R26 -13 dBm signal applied to
600 ohm line input (CN1 pins 1
and 2) 440 mV peak-to-peak
Received signal 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
0 dBm, 5 V peak-to-peak
-13 dBm, 4.5 V peak-to-peak
Received signal 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
0 dBm, 5 V peak-to-peak
-13 dBm, 4.5 V peak-to-peak
Sidetone output IC2a pin 7 More than 0 dBm or -13 dBm
signal applied to 600 ohm line
input (CN1 pins 1 and 2) dc conditions: 6.4 V
0 dBm, 6 V peak-to-peak
-13 dBm, 1.5 V peak-to-peak
Input to loudspeaker
amplifier IC4 Junction of R40
and the volume
control More than 0 dBm or -13 dBm
signal applied to 600 ohm line
input (CN1 pins 1 and 2) 0 dBm, 100 mV peak-to-peak
-13 dBm, 400 mV peak-to-
peak
Loudspeaker
amplifier IC4 IC4 pin 2 More than 0 dBm or -13 dBm
signal applied to 600 ohm line
input (CN1 pins 1 and 2) 0 dBm, +6 Vdc
-13 dBm, +6 Vdc
WARNING Dangerous Voltage