exciter lamp must maintain constant brilliancy,
supply, and 6.5 volts for the transceiver filaments.
since it serves as the source of light which is re-
The primary of T11 is fused by F2, and the circuit
flected from the facsimile copy to the photocell
is completed through ON-OFF switch S2 on the
during transmission of a picture. The exciter
transceiver operating panel. In Rectifier Power
lamp is illuminated only when selector switch S1
Unit PP-86(*)/TXC-1, the starting voltage for
is in the TRANSMIT or SET RANGE position.
the transceiver motor is supplied from the line
Input voltage is applied to V17, which amplifies
through terminals 2 and 4 of the Jones plug when
the signal and applies it to one section of V18.
the START switch is operated. Two capacitors,
This section of V18 serves as the driver for push-
C10 and C11, form a high-frequency suppressor
pull class AB1 tubes V19 and V20. The output of
these tubes is applied to the lamp through one
livered by V22 is filtered by swinging input choke
secondary on T15, and to control voltage ampli-
T12, choke T13, and filter capacitors C12, C13,
fier circuit V21 and V23, through the other second-
and C14. In Rectifier Power Unit PP-86/TXC-1,
ary. Tube V21 varies the amplification of tube
filter capacitor C13 is in parallel with output filter
V17 in an automatic voltage-control circuit.
capacitor C14 (fig. 66). In Rectifier Power Units
a. First Lamp Amplifier (V17) (fig. 68).
PP-86A/TXC-1, PP-86B/TXC-1, and PP-86E/
1,800-cycle signal from the motor amplifier buffer
TXC-1, C13 is in parallel with first filter capaci-
(V3, sections 2, 3, and 4) in the fork oscillator unit
is applied to the injection grid (pin 4) of V17,
82. Exciter Lamp Supply (V17, V18,
type 7S7. This signal is applied through pin 9
V19, V20, V21, V23)
of the power supply plug, coupling capacitor C2,
and the voltage-divider circuit composed of re-
sistors R1 and R2. The grid is bypassed to
The exciter lamp supply, located in Rectifier
ground by C1 to suppress high frequencies. Re-
Power Unit PP-86(*)/TXC-1, receives a con-
sistor R6 is the unbypassed cathode resistor. The
stant-frequency input signal of 1,800 cycles from
control voltage to regulate the amplification of
the fork oscillator unit, amplifies and regulates it,
V17 is coupled from control voltage amplifier V21
and supplies the exciter lamp with an 1,800-cycle
directly to the control grid of tube V17 (pin 6).
signal which remains steady at 6-volt amplitude.
The voltage must be well regulated because the
Capacitor C7 is a smoothing capacitor for the
Figure 68. First lamp amplifier, exciter lamp supply.