TM 11-5805-356-34-1
tion as an oscillator. Capacitor C8 and the in-
C2, ON-OFF switch S9, and fuse F2, to winding
ductance of transformer winding 4-6 determine
1-2 of transformer T1. The 230-volt ac power is
the oscillator frequency, which is approximately
applied to the same connector, but is not applied
55 Hz. Resistors R6 and R7 are current-limiting
across transformer winding 1-2 in series with
resistors. Resistors R2 and R4 establish the base
winding 3-5. This doubles the primary-to-second-
bias of transistors Q2 and Q3. Capacitor C7 pro-
ary turns ratio and maintains the secondary out-
vides feedback to the base of the transistors.
put voltages at the same level as for 115-volt ac
input power. The 26-volt dc power is applied at
d. Power Transformer T1. Power transformer
T1 provides the input ac power requirements for
connector J5, through ON-OFF switch S9, fuse
low voltage rectifier CR2-CR3 and high voltage
Fl, and overvoltage protector Q1-CR1 to inverter
rectifier CR4-CR5. The primary windings pro-
Q2-Q3. When at 26V DC, switch S8 intecon-
vide the flexibility to permit the 26-volt dc invert-
nects the inverter circuit with primary Windbags
of power transformer T1. The inverter circuit
er, a 115-volt ac source, or a 230-volt ac source
then converts the incoming dc to ac and applies
to provide the input power.
this ac power to winding 4-6 in series with series
e. High Voltage Rectifier CR4-CR5. H i g h
winding 7-9 of the transformer.
voltage rectifier CR4-CR5 is a full-wave rectifier
that provides +108 volts dc (5v) to supply
b. Overvoltage Protector Q1-CR1. Overvolt-
the loop current requirements of the associated
age protector Q1-CR1 is a series voltage regula-
teletypewriter equipment. For the receive tele-
tor that protects the inverter circuit, and hence
typewriter, an external power source may be em-
the power supply, from damage if the dc input
ployed to provide the loop current. Connection
voltage rises above 27 volts. When the input
of such a source at EXT. BAT connector J4 dis-
voltage rises above this level, Zener diode CR1
connects the high voltage rectifier as a source of
breaks down, clamping the base of series regu-
loop power for the receive loop.
lator Q1 to -27 volts. As a result, the emitter
f. Low Voltage Rectifier (CR1-CR2. Low volt-
of transistor Q1 cannot rise above -27 volts, and
age rectifier CR1-CR2 is a full-wave rectifier that
the voltage by which the input exceeds 27 volts
furnishes the internal dc power requirements of
is dropped between collector and emitter of tran-
the TH-22/TG. The rectified output voltage is
sistor Q1. The circuits are also protected against
applied to low voltage regulator Q4-CR6 for
the inadvertent application of reversed polarity.
If a polarity reversal occurs, diode CR11 is for-
g. Low Voltage Regulator Q4-CR6. Low volt-
ward-biased, and the resultant heavy current
age regulator Q4-CR6 provides voltage regula-
causes fuse F1 to open.
tion and electronic ripple filtering for the low
c. Inverter Q2-Q3. Inverter Q2-Q3 is con-
voltage power supply. Regulation is provided by
nected to the input circuit of the power supply
Zener diode CR6, which maintains the output
when switch S8 is at 26V DC so as to change
voltage at +18 volts dc (1.8v). Transistor Q4
the 26-volt dc input to ac. When connected
and associated components R8, R9, and C11 pro-
through switch S8, transistors Q2 and Q3 func-
vide electronic filtering.
2-14
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