Tektronix FG 504

Calibration Procedure-FG 504 (SN Β 040000 & UP)
Adjustment Procedure
8 . Adjust L ow Dial W aveform Symmetry (R215)
Set the F G 504 FREQUENCY Hz (START) d ial to 1 and
t he MULTIPLIER to 10 . Set the oscilloscope for d o
coupled normal triggering and ad just sweep speed and
trigger level so one waveform cycle just fills the graticule
h orizontally . Adjust R 215 (LF Sym Cal) on
the Α 3 L OOP
boar d so that
the h alves of the square wave are exactly
equal in time . Disconnect the 50 0 cables and termination
from the F G 504and oscilloscope .
9 . Check Dial
Calibration (R115, R 145) and Adjust
M
echanical Alignment
α . Connect the
F
G
504 TRIG OUTPUT through α 50 Ω
coaxial cable to α 50 Ω termination at the frequency
counter input . Set the F G 504 MULTIPLIER to 10 3
a
nd
t he
FREQUENCY Hz
(START) d ial
to .1
(fully cw) . A d just
R 115 (Min Dial Cal) on Α 3 L OOP boar d for α reading of
150 Hz to 200 Hz on the counter . Setthe
FREQUENCY H z
(START) d ial to 40 and ad just R 145 (
Χ
40
Cal)
on
Α 3 L OOP
board for α counter
d isplay of 40 .0 kHz . Set the FRE-
QUENCY Hz (START)
d ial to 1 ; the counter display should
be 1 .0 kHz . If the reading is correct, ski p p art b a nd
proceed to part c ; if n ot correct,
perform p art b .
b . M echanical dial
adjustment : U se α 1/16" Allen
wrench to
loosen set screws on the dial coupling behind
the front panel . Use long nose p liers to rotate
R
125
potentiometer shaft until the counter
reads 1 .00 kHz . W ith
t he
FREQUENCY H z (START) dial set to 1, tighten the
coupling
set screws .
ε .
Set the FREQUENCY H z (START) dial to 30 and
check t hat STOP FREQ d ial will rotate fully ccw and stop
with t he index mark aligned with t he index markon the
panel . If alignment is correct, p roceed to p art e ;
if not
correct, p erform part d .
d . Use α 0 .050" Allen wrench to loosen t he STOP FREQ
k nob set screws, then r emove the k nob .
Turn the p oten-
tiometer
shaft
to
the ccw endand re-install the STOP
FREQ k nob so index mark is aligned with front panel index
mark . Tighten the set screws .
e . Set the STOP FREQ d
ial fully ccw and check t hat it
stops
with its index mark within a pproximately 5 degrees
of 40 on the FREQUENCY Hz (START) d ial .
410
Th e mec h anical d ial a dj
ustment in p art b must be
performe d wit h th e instrument ope
r ating . E xercise
caution to avoid shorting
out circuitry with Allen
w r enc h or pliers .
f . Re p eat step 9, p arts
α t hrough e, as necessary for
correct
d ial calibration . Disconnect the 50 Ω cable and
termination from the F G 504and counter .
10 . Adjust
R esidual Offset (R1140)
Set the F G 504
ATTENUATOR (dB) to -50 dB . Set all
front p anel pushbuttons to the OUT p osition . Connectthe
F G 504 OUTPUT through α 50 Ω unterminated
coaxial
cable to either the oscilloscope vertical
input or digital
voltmeter
input . Adjust R 1140 (Offset B alance) on Α 1
MAIN b oard for α reading of zero volts ±100 mV on the
oscillosco pe or voltmeter .
11 . Adjust Zero Input Offset
(R1015)
Set the F G 504 ATTENUATOR
(dB)
to
the 0 dB
position . Adjust R 1015 (Input Offset) on the Al MAIN
board for a reading of 0 V±100 mV on
the oscillosco p e or
voltmeter .
Disconnect the 50 Ω cable .
12 . Adjust Output Impedance (C1092)
P ush t he F G 504 square-wave p ushbutton
and the
TRIGGER FREE RUN p
ushbuttonin . SettheMULTIPLIER
to 10 5 and the
FREQUENCY Hz (START) dial to 40 .
Connect two
unterminated 42-inch 50 Ω coaxial cables in
series
with α female-to-female bnc adapter ;
connect one
end to the F G 504 OUTPUT and
the other end to the
oscilloscope
vertical input . Adjust the oscilloscope ver-
tical
sensitivity, triggering (Mode to Auto) and swee p
speed
to display at least one com p lete square
wave cycle
approximately 6-divisions in
amplitud e . Adjust C1092
(Output Impedance) on the
Α 1
MAIN
board for minimum
reflected aberration
behin d t he rising and falling edges of
the square wave . Disconnect
the 50 Ω cables from the
F G 504 OUTPUT and
oscilloscope vertical input .
13 .
Adjust S q uare W ave Amplitude and DC L evel
(R630, R 641)
Connect the F G 504 OUTPUT through α 50 Ω coaxial
cable to α 50 Ω termination at the oscilloscope vertical
input . Set the MULTIPLIER to
102
.
A djust the oscilloscope
vertical sensitivity, triggering,
and sweep s peed to display
at least one cycle of thes q uare wave at α calibrated 2 W div
amplitude . Adjust R 630 (Sq Wave
Am p l Adj)
on
the Α 1
MAIN
board for α p eak-to-peak amplitude of 15 V to
15 .9 V . Set the oscilloscope vertical in p ut coupling to
ground and center the trace vertically . R eturn vertical
i nput coupli ng to d c, and adjust R 641 (Sq W ave Offset Adj)
on the Α 1 MAIN board for square wave
positive and
n egative p eaks equally s p aced above
and below the
graticule center
. Disconnect the 50 Ω cable and termina-
tion from
the F G 504 and oscilloscope .