HP 428B Operating And Service Manual page 50

Model 428B
►New or Revised Item
ERRATA:
Pages 1-0 and 2-1. The power frequency should be 48
- 440 Hz.
Page 1-1. Delete Paragraph 1-5a (the 3528A is
obsolete).
►Page 3-2, Paragraph 3-22. Change last sentence to
read as follows:
"If the jaws mate properly, the zero set should stay
within 0.2 mA, while rotating the probe head with
respect to the earth's magnetic field (probe aligned in
an East-West direction)."
►Page 3-2, Paragraph 3-35. Change the third
sentence to read a follows: "With the RANGE switch at
1 mA, rotation of the closed probe should not vary the
zero set more than 0.2 mA."
Pages 4-0,7-2 and 7-4. Change V3, V4 to CR13
through CR16.
Page 4-3, Paragraph 4-29. Change all "40" to "40
kHz".
Page 4-4, Figure 4-9. Change R87 to R81 . Delete
C12 and return C42 directly to common.
Paragraph 4-49. Delete the words "tube V11" and
insert "Zener diodes CR10, CR17.".
Page 5-0. Change the 50 Ω resistor to 0698-8155.
Change the recommended DC voltmeter to -hp- Model
3469B.
Add: Resistors (2),10 K, 1 %, matched, for alignment,
-hp- Part No. 0757-0442.
Page 5-1, Paragraph 5-2. Add: See the Performance
Test Card at the end of this section."
►Page 5-1, Paragraph 5-11 c. Add the following
sentence: "Point probe in an East-West direction."
Page 5-2. Set the OUTPUT LEVEL control to CAL for
Paragraph 5-18.
►Page 5-3, Paragraph 5-24a. In second sentence,
change reference to 0.1 mA to read 0.2 mA
►Page 5-3, Paragraph 5-28. Replace entire
paragraph with the following:
5-28a. Connect an electronic dc voltmeter to test
point 5 (Pin 1, V9) of the 428B. The voltage at this
point should be 272 ± 6 V; if not, adjust R 109 for
272 V.
b. Measure +12 ±1 V dc between the cathode
of CR 10 and ground.
c. Measure -7 ±1 V dc between the anode of
CR9 and ground.
43
MANUAL CHANGES
Manual Part No. 00428-90003
10 April 1974
►Page 5-3, Paragraph 5-32. Change C10 to L10.
Change C14 to C18.
The 6.3 V filament supply is available at pin 4 or 5 of
V6.
Page 5-3, Paragraph 5-32. Replace entire paragraph
with the following:
5-32. Disconnect FEEDBACK DISCONNECT (See
Figure 7-3); red wire. Place range switch in the 10 amp
position. Adjust fine and course zero controls for
center of travel. Adjust R46 for zero on front panel
meter.
►Page 5-4, Paragraph 5-33. Replace entire
paragraph with the following:
5-33. Reconnect FEEDBACK DISCONNECT.
►Page 5-4, Paragraph 5-42. Add to last sentence"
(2.5 - 3.3 V rms)."
►Page 5-4, Paragraph 5-45. Add the following to
sentence two: ".... carrying 35 mA rms ac, f ≤400 Hz."
►Page 5-4, Paragraph 5-47. Replace the feedback
disconnect before proceeding to Paragraph 5-48.
►Page 5-4, Paragraph 5-47. Add to last sentence: "(.2
V - .4 V peak)"
Para. 5-51. Replace the feedback disconnect before
proceeding to Paragraph 5-52.
►Page 5-5, Paragraph 5-54. Replace entire
paragraph with the following:
►Page 5-5, Paragraph 5-58. Remove Steps a and b.
Re-letter Steps c to f to read a to d respectively. I n
newly designated Step d, Step d is now Step b; Step e
is now Step c.
►Page 5-5. The following paragraph is added
following Paragraph 5-58 to complete the adjustment
procedure:
5-54. Preset the controls as follows:
a. Set RANGE switch to 100 mA
b. Adjust R84 for minimum ac at the
wiper connection of R84. The reading
should be less than 0.1 volts.
c. Adjust R82 for minimum ac out at the
wiper of R82a. The reading should be
≤ 0.02 volts.
d. Thoroughly clean probe head jaws
(See Paragraph 5-7),
e. Degauss probe head (See Paragraph
3-29).