Skanti TRP 5000, Instruction Manual

Page: 79 / 112

5.7.4 High tensions for the P.A. valves are generated by the HT-converter
followed by rectifiers. To avoid excessive anode voltage to the P.A. -
valves at high battery voltages an input voltage sensor is incorporated
in the power pack. When the input voltage exceeds a certain voltage a
relay in the input voltage sensor circuit will operate and decrease the
anode voltage.
Supply voltage f or the driver stage in the transmitter power amplifier
is also generated in the HT-converter followed by rectifiers and a
voltage stabiliser.
The HT-converter is driven from two secondary windings on the LT-
converter transformer.
5.7.5 To fulfil the input voltage requirements of
the blower in the
transmitter power amplifier, a separate blower converter is
incorporated.
5.8 Circuit Description, 24V DC Power Pack P5000
5.8.1 /260\ LT-, HT-, AND BLOWER-CONVERTER
Relay RL1 serves as a mains switch. The current which energises RL1 is
controlled by the POWER switch. Turning the switch from OFF to RECEIVE
ONLY connects the relay coil to the battery voltage. Diode 261 Dl
ensures that the relay cannot operate if the battery voltage does not
have the correct polarity. The contacts of RL1 are protected against
excessive capacitor charging current by resistor R2. The resistor
ensures that the capacitors after the relay are always charged before
the contacts are closed.
The LT-converter is composed of transistors TR10 and TR12, and the
square-wave output signal is coupled through transformer T3 to the LT-
and grid voltage-rectifiers and as a drive signal to the HT-converter.
The HT-converter contains transistors TR4, TR6, TR8 and TR11 and the
output signal is coupled through transformer T2 to the HT-rectifiers.
The Blower-converter contains transistors TRI and TR2 and the output
transformer T1 transforms the square wave output voltage to the correct
level.
Included in the Power Pack is also a loudspeaker connected to the
associated receiver AF-output.
5.8.2 /261\ CONVERTER DRIVER LT-RECTIFIERS AND LT-STABILIZERS.
A bi-stable muiti-vibrator composed of transistors TR2 and TR4 is driven
by oscillator IC1 with a nominal frequency of 440Hz. The output signals
from the muiti-vibrator are therefore square waves with a repetition
frequency of 220Hz, and these signals having a phase difference of 180"
are, after current amplification in transistors TR1 and TR3, used as
driving signals for the LT-converter.
One output signal from the LT-converter is rectified in diodes D11 and
D12 which are followed by two voltage stabilisers both having a nominal
voltage of 7.5 V.
Another output signal from the LT-converter is rectified in diodes D16
and D17 followed by a voltage stabiliser having a nominal output voltage
of 15.7V.