HP 400D, Инструкция по эксплуатации и обслуживанию

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Sect.
IV
Page S
4)
Change input signal to 6. 4 mc and set amplitude
to "SET LEVEL".
5) The reading on the vtvm under test should not
be more than 5%
c1
full scale aoove
0.90.
Any read­
ing below
0 . 90
is acceptable. A high frequency
pt:!ak Is
undesirable at frequencies above
4
mc.
H
the reading is more than 5% high, add capacitor
C40
and resistor R 82
if
not already in the cathode
circuit of V2 in your vtvm. Repeat steps I through
5
if
these parts are added.
The values of
RS2
and
C40
can be adjusted to bring
the 6. 4 mc response below the 5%
maximum. H
you
change either R82 or C40 in value, repeat steps
I through 5.
6) Change the input signal to
10
cps and set the am­
plitude to "SET LEVEL" step
1.
The reading on
the vtvm under
test
should be
0. 90,
±5%
of
full scale.
To increase the
10
cps indication, remove
RBO
if
present in V2 grid circuit. Add Ral in V3 grid cir­
cuit
if
additional increase is needed after
RSO
re­
moval. Conversely, to decrease the indication,
remove RSI and add
RSa
if
necessary. Either but
both resistors can be added. Both resistors
can
be
omitted. A value of 2 . 2 megohms or higher
should be used for
RSO
or RSl when adjusting low
frequency response. Check tubes and coupling capa­
citors if you find that a resistor value below 2.2 meg­
ohms is required.
7)
Inc rease the input signal to about 20 cps and
set the amplitude to "SET LEVEL" of step 1. The
reading on the vtvm under test should not be more
than ±2% of full scale from
0 . 90.
H
necessary,
make compromise resistor adjustments to satisfy
steps 6 and
7.
S)
Switch the vtvm under test to the
0. 003
volt
range . E stablish a new
400
cps "SET LEVEL"
with a reading of
0. 90
on the
0
to
1
scale of the
vtvm under test.
9)
Change
the
input signal to
4
mc and set the input
amplitude to the "SET LEVEL" established in step
B,
Set the reading on the vtvm under test to
0. 90
by
adjusting capacitor C14.
10)
Switch
the vtvm
under test
to the
0.01
volt
range.
Establish a new
400
cps "SET LEVEL" with a read­
ing
of
0. 90
on
the 0 to 1
scale
of
the
vtvrn
under test.
ll)
Change the input signal to
4
mc and set the input
amplitude to the
"SET
LEVEL" establ1shed In step
10.
Set the reading on the vtvm under test to
0. 90
by adjusting - capacitor C16.
12) Check frequency respOnse on
the
0. 03, 0
. 1, and
0. 3
volt ranges. Establish a
400
cps "SET LEVEL"
for each range and then check the response at 4 mc.
H
an error greater than ± 5% of full scale is noted,
make a compromise adjustment
of
C21.
H
the setting
of C2l is changed, repeat all previOUS steps except
6 and 7 The compromise setting of C2l must be
used when repeating step
3.
13)
Switch the vtvm under test to the
1. 0
volt range .
Establish a new
400
cps "SET LEVEL" with a read­
ing
of
0.90
on
the
0
to
1
scale of the vtvm under test.
14} Change the input signal to 2
0
kc
and set the input
amplitude to the "SET LEVEL" established in step
13. Adjust capaCitor C4 for a reading of
O.
90.
15) Change the input Signal to 4 mc and set the am­
plitude to the "SET LEVEL" established in step 13.
The reading on the vtvm under test should not be
more than ±2%
of
full scale from
0. 90.
Adjust R6 in the input divider to bring the
4
mc
response within ±2%. This resistor consists of
several parallel resistors. Increasing the resistance
of R6 will raise the frequency response at
4
mc.
Lowering the re sistance will decrease the 4 mc
response.
16) The frequency response
of
the
3
volt range can
be checked.
H
other ranges have been properly
adjusted
this
range will be
within
specifications.
K.
The following frequency response adjustment pro­
cedure Is based upon the use of the alternate test
eqUipment as explained in paragraph
4-5,
In the
following procedure, test frequencies of 10 cps,
1
mc,
4
mc, and 6. 4 mc are given. The
10
cps and
4
mc frequencies are the band limits of the volt­
meter. The 6. 4 mc check point is for determining
high frequency performance.
The input voltage to the
vtvtrl
under test must always
be monitored by a reference volbneter having a
known
frequency respJnse. The reference voltmeter read­
ing at
400
cps will be called "reference level" in all
steps that follow.
NOTE
The frequency response
controls in the
inst rwne nt
will
prol:ably not need adjustment. These steps have been
included to verify the instrument response and to re­
store proper operation in case
the
original adjustment
is altered. fi'ailure to meet any
of
the following tests
can usually be traced to one or more weak tubes.