11
GRID SIGNAL VOLTAGE TEST
Set
the
BIAS
VOLTS
control
to
zero. Connect a high impedance
AC
voltmeter
to
pins 5 and 8
ofthe
octal socket. Do
not
use
a compensating shunt resistorforthis test. Set
the
FUNCTION
switch
to
positions A
(GO,OOO)
through F
(600) and verify
that
the
voltages are:
A=.25, B=.25,
C=.25, D=.50, E=2.5, F=1.0 volts
AC.
11.1
Adjustment
The
grid signal
is
provided
from
a 5.0
volt
winding
on
the
power
transformer.
If
the
voltages are incorrect measure
the
5.0 volts across taps Rand S on
the
power
transformer
to
verify it
is
correct. Individual grid signal voltages are
obtained by fixed divider resistors
R52
/500
ohms,
R9/
300 ohms,
RI0/
100 ohms,
Rll
/50
ohms and
R12/
so.
Check these resistors
for
proper va lue. If
the
5.0 volts
is
incorrect,
th
is
voltage
is
directly affected by
the
POWER
ADJUST
control. Carefully check
the
UNE
ADJUST
METER
for
inaccuracy and correct
it
as
necessary.
If
however, all
other
operating voltages are correct and only
the
5
VAC
grid
winding
is
wrong, replace
the
grid signal divider
resistor
R52
with
an
appropriate
new
value
to
correct
the
error
and bring
the
grid signal voltages
to
the
specified
values.
12
V.R.
VOlTPJlETER TEST
Set
the
FUNCTION switch
to
the
H
{V.R.
TEST}
position. Connect
the
positive lead
of
a
DC
voltmeter
to
pin 3
of
the
octal socket. Connect
the
negative lead
to
pin
8.
Push
P4
and read
the
voltage. Adjust
the
V.R.
VOLTS
& MILS
controlfora
readingof
150vo/ts. Verify
that
the
main panel
meter
reads 150 volts. Release
P4.
Set
the
V.R.
VOLTS
&
MILS
control
to
zero.
12.1
Adjustment
Check resistors
R20
/ 1K,
R21/
1K,
R22
/ 600 ohms and
R23
/ 470K. Also check
the
main
meter
sensitivity
as
described
in
step
15
(METER
BRIDGE
BALANCE)
below.
13
V.R.
~JlILLIA~JlPERE
METER TEST
Set
the
BIAS
VOLTS!VRVOLTS & MILS (toggle switch)
to
the
VRVOLTS & MILS position. Connect a
2K,
5W,1%
resistor across
the
DC
voltmeter
used
in
the
last test.
Push
P4
a nd adjust
the
V.R.
VOLTS
& MILS control
for
a
reading
of
100
volts.
Verifythatthe
V.R.
VOLTS
&
MILS
meter
is
reading
50
mA.
Release
P4,
disconnect
the
DC
voltmeter
and remove
the
2K resistor. Return
the
BIAS
VOLTSNRVOLTS & MILS (toggle switch)
to
the
BIAS
VOLTS
position. Set
the
VRVOLTS & MILS control
fully
counterdockwise.
13.1
Adjustment
Check resistors
R43
/198
oh
ms
and
R44
/ 2 oh ms.
14 POWER SUPPLY BALANCE CALIBRATION
A.
Set
the
FUNCTION switch
to
the
G (diode rectifier) position. Connect a
DC
coupled oscilloscope
to
pin 3
of
the
octal socket.
Use
pin 8
as
a common
forthe
scope.
Press
P4
(locked). Observe
the
plate voltage and
obtain a
display on
the
scope
that
shows
the
rounded positive peaks
of
the
120Hz (100Hz) pulsating
DC
with
as
high a gain
as
possible. Set
the
vertical position on
the
scope
to
move
the
trace
downward
as
you
adjust
the
gain upward
to
maintain
the
top
of
the
trace on
the
screen. Adjust
R8
for
peaks
of
equal
amplitude. Release
P4.
B.
Connect
the
scope
to
pin 4
of
the
octal socket.
Press
P4
(locked). Adjust
the
scope
as
before
to
display
the
120Hz (100Hz) peaks, and observe
the
screen bias voltage. Adjust
R15
for
equal peaks
ofthe
120Hz
(100Hz) pulsating
DC.
Release
P4
and disconnect
the
scope.
26
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