HP 400F, Operating And Service Manual, Page: 25 / 54

Model 400F /FL
5-30. M
E
T
E
R
CALIBRATION.
30 MV RANGE.
a. Set switch S I to Position A.
b. Set 400F /FL RANGE switch to 30 my. and set
100 KHz L. P. F1LTER switch to OUT.
c. Set voltmeter calibrator for 30
mv output at
400 Hz.
d. Adjust
A2R62
for a 400F /FLmeter Indication
of
30 my.
e. Set switch Sl to Position
B.
f. Adjust test oscillator for a 400F /FL meter
jndication of 30 mv at 400 Hz. Set a reference
on meter of test oscillator and use amplitude
control to maintain reference whenever fre­
quency of oscillator is changed.
g. Set test oscUlator to 20 Hz. maintaining am­
plitude at :iD
mv.
h.
Adjust A2R59 for a 400F /FL meter
indication of 30mv.
i. Set test oscUlator to 4 MHz. maintaining am­
plitude at 30 my.
j . Adjust A2C36 for a 400F /FL meter indication
of 30 mv.
5-31. METER CAIJBRATION. 0. 1 MV RANGE.
N OT E
The O. 1 mv range meter calibration
is performed on a higher range.
This is done by shorting test points
which provide the amplifier with the
addltional l0 db
of gain that normally
is switched in only on the O. 1 mv
range.
a. Set switch SI to Position B.
b. Set 400F/FL RANGE switch to 30 mv. and set
100 KHz 1.. P. FILTER switch to OUT.
c. Adjust test oscillator for a 400F /FL meter
indication of 30 mv at 400 Hz.
d. Set 400F/FL RANGE switch to 100 my.
e. Short TPI toTP4 and short TP2 to TP3. (This
increases the
gain
of the meter amplifier by
10 db, as if the instrument were on the
O.
1 ·
mv range . )
f.
Adjust A2R68 for a 400F/FL meter indication
of 30 mv. (Although the 400F /FL RANGE
switch is in the 100 mv position, the instru­
ment effeeUvely is still on the 30 mv range. )
g. Set test oscillator to 30 Hz. maintaining am­
plitude at 30 mY.
h. Adjust A2R58 for a 400F /FL meter indication
of
30 mv.
5-32. ATTENUATOR AUGNM EN T.
5-33. The follOWing procedures are used to properly
align the input attenuator of the 400F /FL at both high
01795-1
Section
V
Paragraphs 5-30 to 5-42
and low frequencies. Use the test setup shown in Fig­
ure 5-1 for the attenuator alignment.
a. Set switch S1 to Position A.
b. Set 400F/FL RANGE switch to 1 volt. and set
100 KHz L. P. FILTER switch to OUT.
c. Adjust voltmeter calibrator for a 1 volt output
at 400 Hz.
d. Adjust AIR7 for a 400F/FL meter indication
of 1 volt.
e. Set switch SI t o position
B.
f.
Set test oscillator for a 400F /FL meter indi­
cation
of 1 volt at 400 Hz.
g. Set testosclllator t ol00 KHz, maintaining the
amplitude at
1
volt.
h. Adjust AIC2 for a 400F/FL meter indication
of 1 volt. If more than a 1% adjustment is
needed. repeat the 400 Hz adjustment.
5-34. A2Ql BIAS ADJUSTMENT.
5-35. A2R6 provides a bias adjustment for field effect
transistor A2Q1.
a. Monitor voltage at junction between A2R5
and
A2R3 with a dc voltmeter.
b. Adjust A2R6 fora -6v indication at the junct'lon.
5-36. REPLACEMENT OF A2C37
...
.
5-37. The value of A2C37 is individually selected to
compensate for varying circuit parameters within the
instrument. Certain Model 400F /FL instruments
may not have a capacitor in this location.
5-38.
If
an instrument cannot be properly calibrated
on the 30 mv range at 4 MHz, A2C37 shouldbe changed.
Increase the value of A2C37
if
the instrument meter
indication is high and cannot be adjusted low enough.
Decrease the value of A2C37
if
the instrument meter
indication is low and cannot be adjusted high enough.
5-39. TROUBLESHOOTING PROCEDURE.
5-40.
U
the 400F /FL is operating improperly , it either
needs to be calibrated or has a circuit that is mal­
functioning. Troubleshoot the instrument
only
after
it has been determined that the malfunction cannot be
corrected
by
performing the Alignment and Calibra­
tion Procedures in Paragraph 5-19.
5-41. When a malfunction occurs, remove powerfrom
the 400F /FL and visually inspect for loose or broken
wires and connectors. Also check for overheated or
loose components and similar conditions that could
be
a source of trouble.
5-42. The checks outlined in this section were not de­
signed to measure
all circuit parameters. but to
localize the malfunction. Therefore , it is probable
that additional checks and measurements will be re­
quired to completely isolate the faulty component.
5-5