D R A F T
D R A F T
D R A F T
Garex Twomobile
8
Handbook
POWER SUPPLY SECTION
The 12V DC supply is connected to the equipment via the 7A fuses FS1, FS2
and the power switch SI on the front panel. When the equipment is switched
on the positive and negative sides of the supply are connected to the
receiver and the green lamp illuminates. The positive side of the supply is
connected to the DC converter.
The DC converter consists of VT70I, VT702 in a push—pull blocking
oscillator circuit. AC is developed in the secondary of T701, rectified by
a full—wave bridge rectifier MR70I(a-d) and smoothed by C7O1, R701, C702a
and C702b. Another secondary winding provides heater supplies for v601,
V602 via a choke-capacitor filter. When the transmit button on the
microphone is pressed the transmit relay RLB is energised, RLB1 changes
over to break the negative supply to the receiver and connects it to the
converter to provide the HT and heater supplies to the transmitter valves.
The red TX lamp is connected in parallel with the energising coils of RLA
and RLB and illuminates when the microphone switch is operated.
Reversed Polarity Protection
A selenium rectifier MR702 is connected across the DC supply when the power
switch is on and is normally non-conducting. If the supply polarity is
reversed, MR702 will conduct and blow one or both of the supply fuses. It
is vital that the correct fuses are fitted (7A rating, 16mm belling-lee).
RELAYS
The coils of the relays RLA and RLB are each connected to the negative side
of the 12v supply. The positive side is connected to the rel&ys via the
microphone press—to-talk switch.
RLA
is the antenna changeover relay and transfers the antenna
connection from the receiver input to the transmitter output.
RLB
is the transmit relay.
RLB1
transfers the 12V negative supply from the receiver to the DC
converter.
RLB2
transfers the input connection to the audio amplifier (VT503) from the
receiver volume control to the output from microphone preamplifier (VT502).
RLB3/RLB4
transfers the AF output from the loudspeaker transformer T503 to
the modulation transformer T504.
Summary of Contents for TWOMOBILE MK II
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Page 13: ...D R A F T D R A F T D R A F T Garex Twomobile 13 Handbook ...
Page 14: ...D R A F T D R A F T D R A F T Garex Twomobile 14 Handbook SCHEMATICS ...
Page 15: ...D R A F T D R A F T D R A F T Garex Twomobile 15 Handbook ...
Page 16: ...D R A F T D R A F T D R A F T Garex Twomobile 16 Handbook ...
Page 17: ...D R A F T D R A F T D R A F T Garex Twomobile 17 Handbook ...