7 FILAMENT VOLTAGE TEST
Connect
an
AC
voltmeter
to
pins 2 and 7
of
the
octal socket. While
observingthe
readingon
the
meter, rotate
the
FILAMENT
switch
from
the
minimum
th
rough
the
maximum voltage positions a
nd
verify
that
the
voltage agrees
with
the
setting.
The
readings should
be
within
± 10%
of
nominal. Set
the
FILAMENT
switch
to
the
10
volt position.
Set
the
CATHODE
ACTIVITY
switch
to
the
nSf
position. The
filament
voltage should
drop
by
about
10%. Return
the
CATHODE
ACTIVITY
switch
to
the
NORMAL position and set
the
FILAMENT
switch
to
the
6.3 volt position.
7.1
Adjustment
No adjustment. This voltage
is
entirely
dependent
on
the
power
transformer
and
the
AC
line setting. Some
voltages
may read slightly higher due
to
the
lack
of
loading on
the
transformer.
8 PLATE VOLTAGE TEST
Connect
the
positive lead
of
a
DC
voltmeter
to
pin 3
of
the
octal socket. Connect
the
negative lead
to
pin
8.
Push
the
P4
GM
button
a nd read
the
voltage. Norma I plate voltage
is
150
± 5 volts. Release
P4.
Set
the
PLATE
VOLTS
switch
to
the
LOW
position and press
P4.
The reading should
be
65 ± 3 volts. Release
P4
and return
the
PLATE
VOLTS
switch
to
the
NORMAL position.
8.1
Adjustment
No adjustment. This voltage
is
entirely
dependent
on
the
power
transformer
and
the
AC
line setting.
Ifthe
voltage
is
low, check
and/or
replace
the
type
83 rectifier
tube
9 SCREEN VOLTAGE TEST
Move
the
positive lead
of
the
DC
voltmeter
to
pin 4
of
the
octal
socket. Push
P4
and read
the
screen voltage.
Normal
is
130
± 5 volts. Hold
P4
and press
Pl.
The reading should
drop
to
56 ± 3 volts. Release
PI
and
P4.
9.1
Adjustment
No adjustment. This voltage
is
entirely
dependent
on
the
power
transformer
and
the
AC
line setting.
If
the
voltage
is
low, check
and/or
replace
the
type
5Y3
rectifier tube.
Forthe
539C
the
Pi
low
screen voltage
is
not
adjustable.
10 BIAS VOLTAGE RANGE AND VOLTMETER TEST
Connect
the
positive lead
of
a high impeda nce
DC
voltmeter
to
pin
S.
Connect
the
negative lead
to
pin 8. Do
not
use a compensating shunt resistor/or this test. Set
the
BIAS
RANGE
switch
to
the
SOVposition. Adjust
the
BIAS
VOLTS
controlfullydockwise. Verify
that
the
maximum voltage
is
-40 volts. Return
the
BIAS
VOLTS
control
to
the
counter
clockwise, zero volts, pOSition. Set
the
BIAS
RANGE
switch
to
the
10V position. Adjust
the
BIAS
VOLTS
to
-
S.oo
volts
as
read on
the
DC
voltmeter.
Verify
that
the
tester
meter
reads 5.0 volts. Change
the
BIAS
RANGE
switch
to
the
SOVposition. Adjust
the
BIAS
VOLTS
to
-2S.oo volts
as
read on
the
DC
voltmeter.
Verify
that
the
tester
meter
reads 25.0 volts.
10.1
Adjustment
If
necessary, adjust
the
maximum
bias voltage by loosening
the
screw on
the
sliding
tap
of
R18/8.5K
tapped
power
resistor and sliding
it
to
the
position
which
gives
the
correct
reading. This
is
the
tap
with
the
jumper
wire
to
the
end
tab
of
the
resistor. Gently hold
the tap
with
insulated pliers and slide
the
tap
until
the
voltage
is
as
close
to
-40 volts
as
you
ca
n
get
it.
Th
is
adjustme
nt
maya
Iso
affect
the
scree n
vo
Itage
that
was
tested
in
the
previous step. The screen voltage should be retested
if
an
adjustment
is
made.
If
the
bias volts
meter
calibration
is
off
check resistors
R49/40K,
R50
/9.9K
and
R51/200
ohms.
25
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