Introduction; Power Supplies; Ac Operation; Dc Operation - NORTHROP GRUMMAN T6MC User Documentation

Introduction

This topic gives the technical description of the Park Air T6MC controller and details typical operating
conditions to assist fault finding. When reading this topic, reference should be made to
Fig 7-7.

Power Supplies

The T6MC controller operates from either an ac input supply between 110 and 120 Vac, or 220 and
240 Vac. Alternatively, the controller can be used with a dc input supply between 21.6 and 32 Vdc. When
both ac and dc input supplies are connected, the controller continues to operate using the dc supply if
the mains supply fails. Before use, the ac input voltage selector must be set to the correct position
(see page 4-6).

ac Operation

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 during maintenance,
the controller must be isolated from the ac and dc input supplies.
The ac input supply is routed, through the ac connector's fuse and the voltage selector, to the mains
transformer T1. The output of bridge rectifier D15 is routed through the Power On/Standby switch S2 to
voltage regulator IC7. This component provides a 12 V dc stabilized output for the controller's circuits. A
6 Vdc supply, used as a bias voltage, is derived from zener diode D2.
It should be noted that the mains voltage connection to the internal power supply is not disconnected
when S2 is set to Standby.

dc Operation

An external dc supply (21.6 V to 32 V) connected to pins 11 (+) and 12 (-) of the Facilities connector CN1
is routed through fuse FS2 to the reservoir capacitor C1. Diode D1 provides reverse polarity protection
for the equipment. The dc is parallel connected with the bridge rectifier output.

Receive Operation

When the controller is in receive mode, the audio lines are connected to line transformer T2 as follows:
For 2-wire working; directly from Facilities connector CN1 pins 1 and 2

For 4-wire working; from Facilities connector CN1 pins 5 and 7 via relay contacts RLB/1 and

RLB/2. Note that relay RLB energises when the PTT function is active.
From transformer T2, the audio is routed via relay contact RLA/1 (RLA energizes when the PTT function
is active) to the loudspeaker amplifier IC4 and the tape/sidetone amplifier IC2a.
The received audio signal is also routed to the ALC (Automatic Level Compensator) IC1a through relay
contact RLA/1, R26 and C26. The output of IC1a is routed to transistor pair Tr5/Tr6, which control the
input to IC1b. When the input of IC1b rises above the threshold set by R34 and R35, IC1b output rises
causing Tr7 to conduct. When Tr7 conducts, the front panel Busy indicator (D8) lights.

Loudspeaker Switching

When operating with a handset, link LK3 may be removed to enable a cradle switch to automatically
disable the internal loudspeaker when the handset is removed from its cradle.
Park Air T6MC Controller
Dangerous Voltage
Page 5-2
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Fig 7-6 and
Maintenance