Bottom Cover Removal; Bottom Cover Replacement; Adjustment Procedures; Mechanical Meter Adjustment - HP 4328A Operating And Service Manual

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Model 4328A
b. Slide the cover forward, allowmg its forward
edge to enter the groove in the front panel.
c. Replace the cover retaining screw.
5-23,. BOTTOM COVER REMOVAL
a. Remove the retaining screw at the rear of the
cover.
b. Swing the tilt stand out to free the cover.
c. Slide the cover rearward far enough to free the
forward edge.
d. Tilt the forward edge of the cover upward and
lift the cover from the mstrument.
5-24. BOTTOM COVER REPLACEMENT
a. Set the tilt stand out of the wav of the cover.
b.
Rest the bottom cover flat on the cast guides
proJecting inward near the bottom of each side
frame.
c. Slide the cover forward on the guides so that the
formed portion at the rear of the cover slides
over the two short projections at the rear corner
of each side frame.
d. Replace the retaining screw . .
5-25. ADJUSTMENT PROCEDURES
5-26. The following is a complete adjustment and cal-
ibration procedure for the Model4328A. These opera-
tions should be conducted only if it has previously been
established by PERFORMANCE TESTS, that the Model
4328A is out of adjustment. If the procedure outlined
do not rectify any discrepancy that may exist, and all
connections and setting have been rechecked, refer to
TROUBLESHOOTING in Section VIII, for possible
cause and recommended corrective action.
5-27. MECHANICAL METER ADJUSTMENT
a. When the meter is properly zero -set, the pointer
rests over the zero mark on the meter scale
when the instrument is:
(1} at normal operating temperature.
(2) in its normal operating position.
(3) turned off.
b. Set the pointer as follows to obtain best accuracy
and mechanical stability,
(1) Turn mstrument off.
(2)
Rotate the meter mechanical adJustment
screw clockwise until the meter pointer is
to the left of zero and moVIng up the scale
toward zero. Stop when the pointer is ex-
actly over the zero mark. If the pointer
Section V
Paragraphs 5-23 to 5-35
overshoots, repeat step 2.
(3) When the pointer is exactly on zero, rotate
the adjustment screw approximately 3 de-
grees counter-clockwise, This frees the
adjustment screw from the meter suspen-
sion. If the pointer moves during this step,
repeat steps 2 and 3.
5-28. DC POWER SUPPLY CHECK
5-29. Refer to Table 5-4 for Power Supply Check
points and typical voltage values. Measure de voltage
between common and designated Location on Mother-
Board. Measure de ±13V ac ripple withOscilloscope
(HP Model 140A). The peak value of ripple should not
exceed 2mV.
Table 5-4. Power Supply Test
Location on Line
Voltage
Mother-Board
Tolerance
Variation
+13V WHT/RED +12V-+14V
103V-127V
-13V
WHT -12V--14V
5-30. BIAS ADJUSTMENT
5 -31. With the probe leads shorted adjust R360 so
that Q302 collector voltage reads 3. 7V to COMMON.
This sets the bias on Q303 base Oscillator output
transistor.
5-32. T302 ADJUSTMENT
a. Set the Model 4328A to 1m&1 Range with the
probes shorted or 1m&1 across them.
b. AdJust T302 by turning top core cw or ccw for
maximum peak reading. Output is taken at
T301 terminals marked BLU and BLK.
5-33. OSCILLATOR OUTPUT ADJUSTMENT
a. Set the Model 4328A to 100&1 Range with the
probes shorted.
b. AdJust R306 and R360, alternately, for a volt-
age of 200m Vp-p at T301 terminals marked
BLU and BLK (use HP Modell40A).
5-34. ELECTRICAL ZERO ADJUSTMENT
a. Set Model 4328A Range Sw1tch to 100&1,
b. Short the current probes and voltage probes to
each other, for zero mput.
c. RotateR228 clockwise slowly and ascertam that
the Meter pointer moves up scale, and then ro-
tate counterclockwise until pointer reaches
"just" zero.
5-35. LINEARITY ADJUSTMENT
a. Set Model 4328A Range Sw1tch to
lOOn.
5-3