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are connected in parallel with copper oxide rec-
(4) Secondary No. 3 (A, fig. 3) Supplies
tifier CR101 and bridge-balancing resistors
a 5-volt ac signal voltage for mutual
R123 and R125 (and meter shunt resistors
conductance tests. A voltage divider
R131 and R132, when used, on the TV-7A/U).
network consisting of R120, R121, and
At the same time, the rectifier bridge circuit is
R122 (fig. 42-44), connected across
connected between terminals 19 and 37 of T101
this winding, also provides signal volt-
through voltage-dropping resistor R124 and
ages of 1 volt and 0.5 volt, depending
variable resistor R134 (TV-7 B/U and TV-
on the resistor or resistors used.
7D/U only).
d. Filament Supply. Secondary No. 7 of
T101 (A, fig. 3) supplies filament voltage to the
(1) O n the TV-7/U and TV-7A/U, the
tube under test and voltage for rectifier emis-
v a l u e of voltage-dropping resistor
sion tests. Terminals 19 through 37 provide
R124 is such that, when 121 volts ac
voltages from 0 volt to 117 volts, under load.
(no load) exists between terminals
No-load voltages will be slightly higher. As an
19 and 37 of transformer T101, and
example, the no-load voltage measured between
pushbutton 1 -- L I N E ADJ. is de-
terminals 19 and 37 will be approximately 121
pressed, the meter pointer will indi-
volts with 93 volts across the primary. FILA-
cate at LINE TEST.
M E N T VOLTAGE switch S108 is used to
(2) On the TV-7B/U and TV-7D/U, the
select the desired filament voltage for the tube
value of resistors R124 and R134 are
under test. The BLST. position of switch S108
such that, when 121 volts ac (no load)
enables ballast tubes to be tested for continuity,
exists between terminals 19 and 37
and supplies voltage to certain rectifier tubes
of T101 and variable resistor R134 is
for emission tests. Center-tapped resistor R110
properly adjusted, the meter pointer
prevents injection of the filament voltage into
w i l l indicate at LINE TEST when
the grid signal voltage.
pushbutton 1 -- LINE ADJ. is de-
pressed.
7. Line Voltage Test Circuit
c. When power is applied to the test set and
(fig. 3 and 42-44)
the setting of resistor R126 is varied, the volt-
The line voltage test circuit consists prima-
age across the primary and the secondaries of
rily of a bridge circuit connected parallel to
T101 will change. The meter pointer should in-
terminals 19 and 37 of transformer T101. Meter
dicate at LINE TEST when pushbutton 1 --
M101, which can be switched into the bridge
LINE ADJ. is depressed and resistor R126 is
circuit, provides an indication of the proper ad-
properly adjusted.
justments of LINE ADJUST control R126.
d. Current flow through the line voltage test
a. The ac voltage between terminals 19 and
circuit is as follows:
37 of T101 is applied to the rectifier bridge cir-
cuit through part of switch S1101 and re-
(1) When terminal 37 of T101 is negative
sistors  R134  (TV-7B/U  and  TV-7D/U  only)
with respect to terminal 19, the right-
and R124. The rectifier bridge circuit, except
hand part of CR101 will conduct and
for the TV-7A/U, consists of copper oxide
the left-hand part of CR101 will not
rectifier CR101 and bridge-balancing resistors
conduct. Current will flow from termi-
R123 and R125. On the TV-7A/U (fig. 42 and
nal 37 through one part of switch
43), in addition to bridge-balancing resistors
S110-1, variable resistor R134 (TV-
R123 and R125, when meter shunt resistors
7B/U and TV-7D/U only), and volt-
R131 and R132 are used they are also part of
age-dropping resistor R124 to the
the rectifier bridge circuit and are connected in
junction of R123 and R125. The cur-
rent will divide at this point. Some of
parallel with copper oxide rectifier CR101. Re-
sistors R131 and R132 are added to the bridge
the current will flow through R125;
circuit, as required, during initial calibration
the remainder of the current will flow
of the line adjust circuit.
through R123, part of switch S110-1,
b. When pushbutton 1 -- LINE ADJ. is de-
meter M101 and filter capacitor C103,
pressed, meter M101 and filter capacitor C103
and another part of switch S110-1.

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