at least 20 db below the maximum signal (1/10
maximum value on the oscilloscope), it is neces-
a. Wafer Replacement. If a wafer is defective,
sary to improve the balance. This may require
it is easier to replace the wafer than to replace the
changing the photocell or checking the transmit-
entire switch and cable assembly. At the factory,
ting optical system. After proper contrast is
a special socket wrench (fig. 124) is used for re-
obtained between black and white, as adjusted for
moving the nuts of the entire switch assembly.
negative transmission, set the CONTRAST con-
Similar socket wrenches can be made easily in the
trol for positive transmission and obtain as good
field. If materials are not available, long-nosed
a balance on white as possible. Readjust the
pliers will serve the purpose.
balance by adjusting the sliding contact on R42.
b. Grounding Switch. A leaf switch is actuated
If further improvement is necessary, adjust the
by the selector switch when in the transmitting
value of R49, except in TT-1D/TXC-1, TT-1E/
position. This switch grounds the tip of the
TXC-1, and TT-1F/TXC-1 models, by changing
RADIO XMTR jack for the purpose of control-
the resistor to a higher or lower value. The
ling the power relays in the radio transmitter.
balance on either white or black copy of 20 db
Clean and burnish the springs. If proper opera-
below the maximum signal can be obtained by
tion is not obtained after cleaning the springs,
adjusting the CONTRAST control and the
they may be bent for better contact.
sliding contact on R42.
c. Sylus Actuating System. After working the
switch, be sure that the adjustments of the
stylus actuating system are not upset. If the
a. General. The alinement of the signal am-
stroke is too long, make correction by bending
plifier involves nothing more than step-by-step
the actuating arm attached to the selector switch.
checks of signal voltages and waveforms. If
The stylus holder assembly for Facsimile Trans-
there is any deviation from the voltages in the
ceiver TT-1/TXC-1 through TT-1C/TXC-1 is
tracing chart, or if there is any tendency for the
shown in figures 125 and 126. Figure 127 shows
signal to flatten as shown by the oscilloscope,
the stylus holder assembly for Facsimile Trans-
locate the faulty stage and take corrective meas-
c e i v e r s TT-1D/TXC-1, TT-1E/TXC-1, and
ures. All parts may be replaced with approxi-
TT-1F/TXC-1.
mate equivalents, with the exception of trans-
former T2. In emergencies, this transformer can
ceivers TT-1/TXC-1, TT-1A/TXC-1, TT-1B/
be replaced with a driver transformer designed to
TXC-1, and TT-1C/TXC-1, Parts Description
operate into a 6N7 tube or a pair of 6V6 tubes.
Such a transformer should have a turns ratio of
1 to 1 for full secondary. Connect one-half of
the low impedance secondary of the driver trans-
Ref
Function
Name of part and description
Symbol
former to terminals 1 and 2. Leave the other
half of the secondary open. If such an emer-
Supports stylus nec-
STYLUS ASSEMBLY
gency replacment is made, low-voltage line ter-
dle.
minal connections may be obtained by using the
Conducts high volt-
A
STYLUS
a g e to recording
UC feed coil.
paper.
b. Stylus Transformer. Stylus transformer T3
Holder for stylus A.
B
HOLDER, stylus
should be replaced with an exact equivalent. In
Clamps stylus in
SCREW
C
an emergency, a driver transformer, such as one
holder.
designed to operate into a pair of 6V6 tubes or
D
PIVOT,
fixed
Left-hand pivot for
a single 6N7 tube, will serve the purpose. The
stylus shaft.
E
PIVOT,
adjustable
Right-hand pivot for
voltage breakdown rating of the transformer
Stylus shaft.
should be above 2,000 volts. The line side should
S P R I N G , bracket
Spring support for ad-
F
be connected to terminals 1 and 2. A line-to-line
justable pivot.
transformer may be used, but the recording will
BRACKET ASSEMBLY:
Supports pivote.
G
not be at full density.
including fixed pivot.
