HP 427A User manual
 HP 427A
OPERATING AND SERVICE MANUAL
=E-AC-170
SU: 347- 007 78
PROPERTY OF
ELECTRICAL ENGINEERING
TECHNICAL LIBRARY
VANDERBILT UNIVERSITY
VOLTMETER
427A
In dim 174:
|
1
il
PACKARD
HEWLETT i
Vict dH
a RESTA ta re Pe. | "ENTES IE PER EEE EE PE PE a UPRO "e AE . | : = ? т FE Lala N i .
a + a Cae ' . cea Lo . . : - - - -
# : .
f +
x
= E = 2
: « :
- + 4
„X =
x
= = = =
: He
В - -
L
x
Ti
rÉ
>
a
$
K4XL's “®- BAMA
This manual is provided FREE OF CHARGE from
the "BoatAnchor Manual Archive” as a service to
the Boatanchor community.
It was uploaded by someone who wanted to help
you repair and maintain your equipment.
If you paid anyone other than BAMA for this manual,
you paid someone who is making a profit from the
free labor of others without asking their permission.
You may pass on copies of this manual to anyone
who needs it. But do it without charge.
Thousands of files are available without charge
from BAMA. Visit us at http://bama.sbc.edu
|
OPERATING AND SERVICE MANUAL
-hp- Part No. 00427-90004
MODEL 427A
VOLTMETER
Serials Prefixed: 947-
Appendix C, Manual Backdating Changes,
adapts manual to serials prefixed 550-, 621-, 731-
Copyright Hewlett-Packard Company 1969
Р.О. Вох 301, Loveland, Colorado, 80537 U.S.A.
Printed: JAN 1970
ii и _ | = o "to o" A ||| dE C . I - a - _ Я
@ a Model 427A Table of Contents
TABLE OF CONTENTS
Section Page Section Page
I GENERAL INFORMATION. . ...... 1-1 V MAINTENANCE (Cont'd)
1-1, Description. . . ....... .. 1-1 9-7. AC Accuracy and Frequency
1-5. Battery . . . . .......... 1-1 Response Check. . . . . . .. 5-1
1-7. Instrument and Manual 9-14. Resistance Accuracy Check. . 5-2
Identification. . . . ....., 1-1 5-16, DC Accuracy. ., ....... 5-2
1-10. Available Accessories . . .... 1-1 5-18. AC Rejection Check. ., ... 5-3
1-12. Cables and Adapters ..... 1-1 5-20. Input Impedance Check .... 5-3
1-13. Probes, . ....... e... 1-1 9-25, Adjustment and Calibration
Procedures . ........ ‚ 5-4
Section Page 5-217. Cover Removal ........ 5-4
II INSTALLATION +... 44 1 2 2 4 4 4 à. 2-1 5-30. Amplifier Balance and Zero
2-1, Introduction. . ..,........ 2-1 Offset Adjustment, . . ... 5-5
2-3. Initial Inspection . . . . . e... 2-1 0-31. Regulator Adjust . .... .. 2-2
2-5, Power Requirements. ...... 2-1 0-32, AC Calibration. . . . . .... 5-5
2-7. Grounding Requirements . , .. . 2-1 5-36. Resistance Infinity Adjustment 5-6
2-10. Installation . . .......... 2-1 0-38. DC Calibration. . . . . . . . . 5-6
2-12, Bench Mounting .. ...... 2-1 5-40. Alternate Performance Checks
2-14. Rack Mounting. . ., . . . e. 2-1 and Calibration Procedures. . 5-6
2-16. Combination Mounting .... 2-1 5-42. AC Circuits . . . . . e e... 0-6
2-18. Repackaging for Shipment . . . . 2-1 5-45. Resistance Circuits. . . . .. 5-6
5-47. DC Circuits . . ,..,..... 5-7
Section Page 9-50. AC Rejection . . . . ...., 5-7
III OPERATING INSTRUCTIONS ...... 3-1 5-52. Input Impedance Check . . . . 5-7
3-1, Introduction. . .......,... 3-1 5-54. Battery Replacement. . . . . . . 5-7
3-3. Front and Rear Panel 5-56. Troubleshooting. ......... 5-7
Description . . . . .. . .. . 3-1 5-60. Power Supply . ........ 5-8
a 3-5 Operating Instructions .. . . . . 3-1 5-63. DC Amplifier . . ....... 9-8
| 3-6 Mechanical Zero Adjustment . 3-1 5-67, AC Metering Circuit. . . ... 5-8
| 3-8 Turn-On Procedure. ., .. , 3-1 5-71. Adjustment of Factory Selected
3-11 DC Measurements, . . . . . . 3-1 Components . . . . . . er... 5-8
3-12. Resistance Measurements . . 3-1 5-73. AIR19*, . . . . ........ 5-8
3-13. AC Measurements. . . . . .. 3-2 5-75 A2C2*#* 2 42 2 2 4 4 + 4 5-9
3-16 DB Measurements, , . . .. . 3-2 5-71. A2R14* aaa remo... . 5-9
5-80. A2R18* . .... 14 + + + . . 5-9
Section Page 9-82. Etched Circuit Board Repair. . . 5-9
IV THEORY OF OPERATION, , ....... 4-1
4-1. General. .............. 4-1 Section Page
4-5. DC Operation. . .......... 4-1 YI CIRCUIT DIAGRAMS. , , . .. .... . . 6-1
4-7. 'Ohms Operation . .......oo 4 6-1, Introduction ..,.......... 6-1
4-9, ACOQperation. . .......... 4-1
4-12. Circuit Descriptions, . ..... . 4-2 Section Page
4-13. DC Amplifier (A1). .. . .. . . 4-9 VI REPLACEABLE PARTS . .. .. . .... 7-1
4-16, DC Offset (A2) ......... 4-2 7-1, Introduction ............ 7-1
4-19. AC Metering Circuit (A2). . . . 4-3 7-4. Ordering Information. . ..... . 7-1
4-23. Battery Regulator A1. . . . . . 4-3 7-6. Non-Listed Parts. . . . . . ‚к... 7-1
Section Page Appendix
у MAINTENANCE , ............. 5-1
9-1. Introduction , ...,........ 5-1 A CODE LIST OF MANUFACTURERS
9-3. Required Equipment . . . ..... 5-1 B SALES AND SERVICE OFFICES
9-9. Performance Checks ..,....,. 5-1 C MANUAL BACKDATING CHANGES
LIST OF TABLES
Number Page Number Page
1-1, Specifications . . . ........... 1-0 5-3. 1% Resistors. . . ..... ..e..... 5
3-1, Efiects of Harmonic Distortion. .... 3-2 5-4, Troubleshooting , . ......... .. 5-7
3-2. DB Range Identification. . . . ... ‚ ‚ 3-2 9-5. Power Supply Voltages , . ....... o~8
Del, Required Test Equipment, . . .... . 5-0 9-6. AC Metering Circuit Voltages . . . . . 5-8
9-2. Resistance Accuracy Check. ‚ . . . . . 5-2 7-1, Replaceable Parts. . .......... 7-1
01791-2
iii
Table of Contents
Number
1-1. Model 427A Voltmeter , . . . . »
1-2, 11096A High Frequency Probe. .
3-1, Location of Front Panel Controls
and Indicators. . . = + « + «
3-2. Impedance Correction Graph . .
4-1. Simplified Block Diagram . . . .
-2. DC Operation. . + « к ¢ « « = «
iv
Ohms Operation .. +. +. + +»
AC Operation ... ++ ++ <<
DC Offset Circuit, . . . . + += =
AC Accuracy and Frequency
Response Check. . . + < + + =
—]][ y EE El
Model 427A
OF ILLUSTRATIONS
Page Number Page
. 1-0 5-2, Resistance Accuracy Check. .. . . . » 5-2
‚ 1-1 5.3. DC Accuracy and Linearity Check. . . . 5-2
5-4, AC RejectionCheck . . . + «+ ++ + >" 5-3
‚ 3-0 5-5, Input Impedance Check . . + + + кое + © 5-4
‚ 3-3 5-6. Location of Internal Adjustments . ., . . 5-5
. 4-0 5-7, Battery Replacement, . . ..rererre 5-7
+ 4-1
. 4-2 6-1. Location of Switch Components . . + + 6-2
4-2 6-2. Component Location . . . «+ + ++ +" » 6-3
4-3 6-3, Schematic Diagram . + + + 4 + + +" + 6-3
‚ 5-0 71. Location of Mechanical Parts . . . . . . 7-0
01791-2
a
section I
- FRNCTION 5
Model 42TA
dt HG
И daR Ti
>
@ 4274 VOLFMETER
=} "RANGE
Figure 1-1. Model 427A Voltmeter
Table 1-1.
Specifications
DC VOLTMETER
Voltage Ranges: +100 mV to +1000 V full scale in a
1, 3, 10 sequence (9 ranges).
Accuracy: +2% of full scale on any range (0°C to
50°C).
Input Resistance: 10 megohms on all ranges.
AC Rejection: Superimposed peak ac voltages (60
Hg and above) 100 times greater thanfull scale
affects reading less than 1%. Maximum 450
volts peak.
Overload: 1200 Vdc on any range.
AC YOLTMETER
Voltage Ranges: 10 mV to 300 V rms full scale in a
1, 3, 10 sequence (10 ranges).
Frequency Range: 10 Hz to 1 MHz.
Accuracy: (0°C to 50°C),
RANGE +2% OF FULL SCALE
0.01 Y - 30 Y 10 Hz - 1 MHz
100 Y - 300 Y 10 Hz - 100 KHz
Frequency Response:
IHZ ЭН: IOHz | MHz
Frequency response 10 mV to 30 V ranges.
CMHz 3MHz 4MHz
AC VOLTMETER (Cont'd)
Input Impedance; 10 megohms shunted by 40 pF on 10
mV to 1 V ranges; 20 pf on 3 V to 300 V ranges.
Response: Responds to the average value of the in-
put; calibrated in rms volts for a sine wave input.
Overload: 300V/rms momentarily, 1V range and
below,
425 V/rms maximum above 1V range.
OHMMETER
Resistance Ranges: 10 ohms center scale to 10 meg-
ohms center scale (7 ranges).
Accuracy: +59 of reading at midscale (0°Cto +50°С),
Polarity: Common terminal negative,
Source Current:
OPEN CIRCUIT | SHORT CIRCUIT
RANGE VOLTAGE CURRENT
X10 0.1V 10 mA
X100 0.1 V 1 mA
X1K 1 Y 1 má
X10K 1 y 100 ¡A
X100K 1 y 10 uA
X1M 1 Vv 1 uA
X10M 1 y 0.1 LA
GENERAL
Floating Input: May be operated up to 500 Vdc above
ground. (Ohms input open in any function except
ohms--volts input open when instrument is in off
position, )
Power: 22-1/2 volt dry cell battery. (Eveready No.
763 or RCA VS102. }
Option 01: Battery operation and ac line opera-
tion (selectable on rear panel), 115 or 230 Y
+20%, 50 Hz to 400Hz, 1/2 W.
1-0
01791-2
q
M a
pa
Model 427A
Section I
SECTION |
GENERAL
1-1. DESCRIPTION.
1-2. The Hewlett-Packard Model 427A is aversatile,
compact, self-contained voltmeter. It is capable of
making de measurements from 1 mV to 1000 volts, ac
measurements from 0. 3mVto 300 volts at frequencies
from 10 Hz to 1 MHz, and resistance measurements
from 0.2 ohms to 500 megohms. With the 01 option,
the Model 427A may be powered either by a 115 or
230 volt line or by an internal 22-1/2 volt dry cell
battery.
1-3, The use of solid state components throughout
gives the Model 427A both ruggedness and reliability,
Battery operation makesthe instrument ideal for field
use or isolation from common mode ground loops,
1-4, Figure 1-1 showsthe Model 427A, and Table 1-1
contains a list of the Model 427A Specifications,
1-5. BATTERY.
1-6. The battery used in the Model 427A is a 22-1/2
volt dry cell, Eveready No. 763 or an RCA \5102.
Typical battery life is morethan 300 hours continuous
operation or 700 hours intermittent operation.
1-7. INSTRUMENT AND MANUAL
IDENTIFICATION.
1-8, Hewlett-Packard uses a two-section eight-digit
serial number (000-00000). If the first three digits
(prefix) of the serial number on your instrument do
not agree with those on the title page of this manual,
INFORMATION
change sheets supplied with the manual will define
differences between your instrument and the Model
427A described in this manual.
1-9. If a letter prefixes the serial number, the
instrument was manufactured outside the United
States.
1-10. AVAILABLE ACCESSORIES.
1-11. The following accessories are available to in
crease the test capabilities of the Model 427A.
1-12. CABLES AND ADAPTERS,
-hp- 11001A 45" test lead, dual banana to BNC
male
-hp- 11002A 5' test lead-dual banana to alligator
clips
-hp- 11003A 5' test lead-dual banana to pencil
probe and alligator clip
-hp- 10111A shielded BNC female to banana
plug adapter
1-13. PROBES.
-hp- Model 11074A 10:1 Voltage Divider Probe
extends the voltage range of Model 427A by a
factor of 10.
-hp- Model 11039À 1000:1 Capacitive Voltage
Divider for measuring voltages up to 24 KV.
-hp- Model 11096A High Frequency Probe ex-
tends the frequency range of the 427A to 500 MHz.
The voltage range is 0.25V to 30V.
Figure 1-2.
01791-2
11096A High Frequency Probe
e.
ea
Model 427A
Section I
SECTION Il
INSTALLATION
2-1. INTRODUCTION.
2-2, This section contains information and instruc-
tions necessary for installation and shipping of Model
427A Voltmeter, Included are initial inspection pro-
cedures, power and grounding requirements, install-
ation, and instructions for repackaging for shipment,
2-3. INITIAL INSPECTION.
2-4. This instrument was carefully inspected both
mechanically and electrically before shipment. It
should be physically free of mars or scratches and in
perfect electrical order upon receipt. To confirm
this, the instrument should be inspected for physical
damage in transit, Also, test the electrical perform-
ance of the instrument using the procedure outlined in
Paragraph 5-5. If there isdamage or deficiency, see
the warranty on the inside front cover of this manual,
2-5. POWER REQUIREMENTS.
2-6, The Model 427A uses a 22, 5 volt dry cell battery
for its primary power source. However, if Option01
is included, the Model 427A can be operated from any
source of 115 or 230 volts (+20%) at 50 to 400 Hz.
With the instrument disconnected from the ac power
source, move the elide switch (located on the rear
panel) until the desired line voltage appears. Power
dissipation is less than 1/2 watt maximum,
2-7. GROUNDING REQUIREMENTS.
2-8. To protect operating personnel, the National
Electrical Manufacturers" Association (NEMA) recom-
mends that the instrument panel and cabinet be ground-
ed. The Option 01 427A is equipped with a three-
conductor power cable which, when plugged into an
appropriate receptacle, grounds the instrument. The
offset pin on the power cable three-prong connector
is the ground wire.
2-9, To preservethe protection feature when operating
the instrument from atwo-contact outlet, use a three-
prong to two-prong adapter and connect the pigtail on
the adapter to ground,
2-10. INSTALLATION.
2-11. The Model 427A is fuily transistorized; there-
fore, no special cooling is required. However, the
instrument should not be operated where the ambient
temperature exceeds +55%C (1310F), For additional
information, address inquiries to your local -hp-
Sales and Service Office. (See Appendix B for office
locations.)
2-12, BENCH MOUNTING.
2-13, Model 427A is shipped with plastic feet and tilt
stand in place, ready for use as a bench instrument.
01791-3
2-14, RACK MOUNTING.
2-15, Model 427A may be rack mounted by using an
Adapter Frame (-hp- Part No. 5060-0797). The adapt-
er frame is a rack frame that accepts any combination
of submodular units. It can be rack mounted only.
2-16, COMBINATION MOUNTING.
2-17. The Model 427A may be mounted in combination
with other submodular units by using a Combining Case
(-hp- Model 1051A), If the 427A is equipped with a
carrying handle, it will be necessary to remove the.
top cover on 427A before inserting it into the Com-
bining Case. The Combining Case is a full-module
unit which accepts various combinations of submodular
units. Being a full-module unit itself, it can be bench
or rack mounted and is analogous to any full-module
instrument.
2-18. REPACKAGING FOR SHIPMENT.
2-19. The following paragraphs contain a general guide
for repackaging of the instrument for shipment, Refer
to Paragraph 2-20 if the original container is to be
used; 2-21 if it is not,
NOTE
If the instrument is to be shipped to
Hewlett-Packard for service or repair,
attach a tag to the instrument identifying
the owner and indicating the service or
repair to be accomplished; include the
model number and full serial number of
the instrument, In any correspondence,
identify the instrument by model number,
serial number, and serial number prefix.
2-20. I original container is to be used, proceed as
follows:
a. Place instrument in original container. If
original container is not available, a suitable
container can be purchased from your near-
est -hp- Sales and Service Office,
b. Ensure that container is well sealed with
strong tape or metal bands,
2-21, If original container is notto be used, proceed
as follows:
a. Wrap instrument in heavy paper or plastic
before placing in an inner container.
b. Place packing material around all sides of in-
strument and protect panel face with cardboard
strips.
с. Place instrument and inner container ina heavy
carton or wooden box and seal with strong tape
or metal bands.
d. Mark shipping container with "DELICATE
INSTRUMENT, '"" "FRAGILE" etc,
2-1
Section II
Model 427A
MODEL 427A TRONT PANEL
il ” vdd, a
a res A me 7
SN > EL NA
& enn ZN
10 tom = ‚7754 A
de HEWLE}1 - PACKARD / 4274 VOLTMETER
(1-7 FUNCTION RANGE
АСМ XIOK
XI | 3 IO XIQOK
xIdO L3 30 XIM
xo 1 O0 XIOM
.53 300
AZ
- ONLY [ be
15% MIN. ‚ol 1200 — о
OT 5 vous оны:
LK {Rm
5» »
BATT/LINE (option 01 only) slide switch: Se-
lects either battery or line operation.
De ZERO 0
427A-8-0529
115/230 slide switch (option 01 only): Selects
either 115 Vac or 230 Vac for line operation,
Line input (option 01 only): Connects ac
operating power to instrument.
RANGE switch: Selects appropriate range of
unknown input.
DC ZERO/Q e thumbwheel: Usedto electrical -
ly zero the instrument in DC mode and to infinity -
set the instrument in OHMS mode.
© © © © ©
OHMS terminal: Connects unknown resistance
to instrument.
MODEL 427A REAR PANEL (CPTION Ol)
BATT RFQ
O
O
LINE
O TES
\
COM terminal: Connects to instrument com-
mon. (Common input for ACV, OHMS and
Dev.)
(8) VOLTS terminal: Applies unknown ac or dc
voliage to instrument.
FUNCTION switch: Selects mode of operation.
Selections are OFF, BATT, +DC, -DC, OHMS
and AC.
Mechanical zero: Mechanically zeroes the
meter.
(1) Meter face: Displays the magnitude of unknown
resistance or voltage in ohms or volts respec-
tively.
Figure 3-1. Location of Front Panel Controls and Indicators
01791-2
д м
AM A
д а
у <
—— р” ————— - —— = = Л
Model 427A Section II
SECTION III
OPERATING INSTRUCTIONS
3-1. INTRODUCTION. 3-10. OPTION 01 INSTRUMENT.
. Select either battery or line operation withthe
3-2. The Model 427A may be operated as a dc volt- a ; ;
meter, ac voltmeter, ohmmeter or dB meter, This tery panel BATT/ LINE slide switch. > er
section contains operating instructions for each mode I'y operation 1s selec 3 a, © © ery
of operation, according to Paragraph 3-9.
b. I line operation is selected, set the 115/230
3-3. FRONT AND REAR PANEL DESCRIPTION. slide switch to indicate the proper line volt-
age,
3-4, Figure 3-1 shows the location of all the Model , ;
427A controls and indicators and explainsthe function ©. poate the D УТОК swith to he desired /
of each. The Option 01 rear panel is shown, The unctlon. uring line operation, the T
standard rear panel is blank 1.5 MIN check position displays the output of
pan * the Option 01 power supply. The reading
should be 1, 5 or higher on the 0-3 scale on
3-5. OPERATING INSTRUCTIONS. any range, indicating a power supply output
NOTE of 15 volts or more. This serves as a con-
venient check of the Option 01 power supply.
To obtain maximum battery life,
set the FUNCTION switch of OFF 3-11. DC MEASUREMENTS.
when the instrument is not in use, a. Rotate the FUNCTION switch to +DCV or
3-6. MECHANICAL ZERO ADJUSTMENT. -D CV depending on the polarity of the input.
b. Short the VOLTS input tothe COM input, ro-
3-7. Before any measurements are made, complete tate RANGE to 0. 1, and adjustthe DC ZERO/
the Mechanical Zero Adjustment inthe following steps. Q« thumbwheel for zero meter deflection.
. с. Remove shorting connection. If there is a
a. Be sure instrument has been off for at least zero offset with COM and VOLTS open, refer
- to Paragraph 4-18 and Paragraph 5-30.
b. Rotate Mechanical Zero Adjustment screw d. Select approximate range of input with RANGE
CLOCKWISE until meter pointer isto the left switch.
of zero and moving upscale toward zero,
с. Continue to rotate adjustment screw clockwise,
STOP when needle is exactly on zero. If
needle overshoots, repeat step b. DO NOT APPLY MORE THAN
1200 VDC TO ANY DC RANGE.
d. When pointer is exactly over zero, rotate
adjustment screw slightly COUNTERCLOCK- e, Connect input across VOLTS and COM ter-
WISE to relieve tension on suspension. If minals and read magnitude of input on meter.
the pointer moves to the left, repeat whole
procedure, but make the counterclockwise 3-12. RESISTANCE MEASUREMENTS.
rotation less.
3-0. TURN-ON PROCEDURE.
DAMAGE TO 427A INPUT CIR-
3-9, STANDARD INSTRUMENT. CUIT MAY RESULT IF DC OR
AC VOLTAGE IS APPLIED TO
a. Rotate the FUNCTION Switch to BATT/1. 5 OHMS TERMINAL.
MIN position. a. Rotate the FUNCTION switch to OHMS.
b. The meter should read 1.5 or higher on the b. Selectthe approximate range withthe RANGE
~ a
0-3 scale on any range, indicating that the
battery voltage is 15 volts or higher. If the
reading is below 1.5, replace the battery
according to the steps in Paragraph 5-54.
01791-2
switch; and withthe input terminals open, ad-
just the DC ZERO/Qw thumbwheel Рог ап =
indication onthe ohms scale. {Pointer should
rest on the mark just to the left of =).
3-1
Section II
C. Connect the unknown resistance across the
OHMS and COM terminals. Read the resis-
tance value on the ohms scale.
NOTE
For best accuracy, select an
ohms range -that will place the
meter pointer near the center
of the scale,
3-13, AC MEASUREMENTS.
3-14, The Model 427A responds to the average value
af the ac input and is calibrated in rms volts for a
sine wave input. Since the average value and the rms
value of a non-sinusoidal signal are different, any
distortion on the input will affect the accuracy of the
reading. Table 3-1 shows the effect of harmonic dis-
tortion on a reading.
NOTE
The following table is uni-
versal in application since
these errors are inherent in
all average-responding volt-
meters. The error shown above
may vary with the phase relation-
ship between the harmonic and
fundamental.
Table 3-1. Effects of Harmonic Distortion
INPUT VOLTAGE TRUE RMS METER
CHARACTERISTICS VALUE INDICATION
Fundamental = 100 100 100
Fundamental + 10% 100.5 100
second harmonic
Fundamental + 20% 102 100 - 102
second harmonic
Fundamental + 50% 112 100 - 110
second harmonic
Fundamental + 10% 100. 5 96 - 104
third harmonic
Fundamental + 20% 102 94 - 108
third harmonic
Fundamental + 50% 112 90 - 116
third harmonic
3-15, Use the following stepsto make an ac measure-
ment.
a, Rotate FUNCTION switch to ACY,
NOTE
With the input shorted, there
may be a zero offset of about
two minor divisions. This is
caused by the bias current through
the meter bridge and does not affect
the accuracy of ac measurements as
the meter moves upscale,
3-2
Model 427A
b. Rotate RANGE switch to approximate range
of input voltage.
DO NOT APPLY MORE THAN 425V
RMS WHEN THE INSTRUMENT IS
ON RANGES ABOVE 3, OR MORE
THAN 300V RMS ON RANGES BE-
LOW 3.
с. Connectthe signal to be measured to the
VOLTS and COM terminals and read the
magnitude on the voltage scale.
3-16. DB MEASUREMENTS.
a, Making a dB or dBm measurement is essen-
tially the same ag making an ac voltage mea-
surement, Followthe steps in Paragraph 3-13,
but read the magnitude on the dB scale.
b. The 1 volt position of the RANGE switch is
the 0 dBm range. Each position above 1 volt
is a 10 dB increase, and each position below
1 volt is a 10 dB decrease. Table 3-2 lists
the dB value of each range,
Table 3-2. DB Range Identification
RANGE DB RANGE DB
300 +50 1 0
100 +40 0.3 -10
30 +30 0.1 -20
10 +20 0.03 -30
3 +10 0,01 -40
с, A given dB reading is equal to the algebraic
sum of the range andthe meter reading. For
example, if the meter reading were -6 and
the instrument were on the 10 volt (+20 dB)
range, the final reading would be 20 dB -
6 dB = 14 dB.
d. The 427A meter is calibrated in dBm. 0dBm
is equivalent to 0.775 volt dropped acrossa
60092 load. Consequently, any dBm measure-
ments must be made across atotal impedance
of 60082. Measurements across other imped-
ances will be in dB, not dBm,
e. To convert a dB reading to dBm, use the Im-
pedance Correction Graph (Figure 3-2). For
example, to convert a +30 dB reading made
across a b0Q load to dBm, locate the 502
load impedance on the bottom of the graph.
Follow the impedance line to the heavy
black line and read the meter correction
at that point. The correction for 509 15
+10. 5 dBm, and the corrected reading is
+40. 5 dBm.
01791-2
BE
д æ
a A
a ‚- E ДН mn 5 = о 1 . = a *
Model 427A Section III
A a
+25
+20
+15
+
o
+
Cn
METER CORRECTION - DBM
—20
— 25
| 10 100 IK lOK I00K
IMPEDANCE —- OHMS
STL-A-0D4TT
~ a
Figure 3-2. Impedance Correction Graph
01791-1 3-3
пад
E ad Ted LA emt A Td © eff Fall ef Tut А! Дан, MY] We = me = FR TE E o
in
` «а
MEM
< WEISE NOTE PSIAIdUWIS “[-p eINdIA
Si
=H
©
®
=
voy- vit
SITOA L'9—
397 104 NONIWOS “Y solv oan le—o—" | Aauarive
AldeNs AU3LLVE o
S110A 29+
(2v) _Linowio Lo | MOLVANSLLY HOLYNNILLY | os HT an
ONINILIW OV 1504 2% 3ONVYH OV HIMOd
| 10 NOILdO
(17) | 199 SIWHO y
| wat MOLYNNILIY [*——sWnol #0L9313S LAENI SLTOA
HE sa y 39NVH SWHO 57 NOI LINN
- E
(27)] 7179 90 29+ ANNI SHO
НЭ) Зи
E
(2 Lsnrav ty) HOLVNNILLv
135330 90 Mal [| 3nvu 50
-
pl
=
a
©
db
52
01791-1
4-0
A a
A a
уж <.
Model 427A
Section 1V
SECTION IV
THEORY OF
4-1. GENERAL.
4-2. The Model 427A measuresac voltage, dc voltage,
and resistance. It is battery operated, but with Op-
tion 01, can be powered by line voltage. Figure 4-1
shows a simplified block diagram of the 427A,
4-3. The Battery Regulator (Al) regulates the bat-
tery output and provides +6. 7 and -6. 7 volt bias sup-
ply to the amplifiers. The 427A uses two amplifiers,
the DC Amplifier (Al) and the AC Metering Circuit
(A2). The former is a high input impedance unity
gain amplifier used toamplify de and resistance inputs.
It also serves as a preamplifier for ac signals. The
AC Metering Circuit amplifies ac signals from the
preamplifier, converts them todc signals proportional
to the average ac, and connects them to the meter.
The meter is calibrated to display the rms value of
the ac input.
4-4. The DC Offset Adjust (A2) compensates for
leakage current from thede amplifier, and DC CAL and
OHMS CAL areresistive circuits used for calibration.
4-5. DC OPERATION.
4-6. Figure 4-2 shows the Model 427A in the DC Mode
of Operation. The dc input is first applied to the DC
Range Attenuator where it is attenuated by 10dB for
each step ofthe attenuator. Thedc signal from the at-
tenuator goes to the DC Filter, and the filter rejects
any ac superimposed noise that may be present on the
input. The dc output of the filter goes to the DC Am-
plifier (A1) and then to the meter. The DC Amplifier
matches the high impedance of the attenuator to the
low impedance of the meter, The DC CAL circuits
OPERATION
are resistive circuits in series with the meter used
to adjust the meter current to calibrate the lower
ranges.
4-7. OHMS OPERATION.
4-8. Figure4-3is ablock diagram of the Model 427A
in the OHMS Mode of Operation. With the input open,
Ra and Ry, forma voltagedivider. The voltage across
R, causes full scale current toflow through the meter.
The OHMS CAL circuit adjusts the meter current for an
indication of = with the input open. When R, is equal
tothe parallel combination of Ry; and Ry, the total re-
sistance from the OHMS terminal to ground will be
half the parallel combination of R, and Ry,, the voltage
into the amplifier will be halved, and the meter indi-
cation will be half scale. The Model 427A is designed
go that the full RANGE setting will be displayed in the
center of the scale. For example, 10 £ on the X10
range is a center scale reading.
4-9. AC OPERATION.
4-10, Figure 4-4 shows a block diagram of the 427A
in the AC Mode of Operation. The input signal goes to
the AC Range Attenuator. On the 1 volt range and be-
low, the signal is not affected by the AC Range Attenuator;
but on all the higher ranges, the signal is attenuated
by 50dB. Capacitor C3adjusts the frequency response
of the attenuator with a 3 volt 100 KHz input. The
signal from the AC Range Attenuator goes through
the DC Amplifier to the AC Post Attenuator where it
is attenuated by 10 dB for each step of the RANGE
selector. The DC Amplifier matches the low impe-
dance of the Post Attenuator to the high impedance of
the Range Attenuator, acting as a preamplifier.
ATTENUATOR —a—
| 2 7 1 FILTER AMPLIFIER
| © A
! 1 FEEDBAC
E In 9— 0 к
1 DE
| CAL
COM I
427A-R0 | |
Figure 4-2. DC Operation
01791-2 4-1
Section IV Model 427A
OHMS
ÂT TENUATOR
# %
+6.7V
Ра? © 2-=-—--
DC
7 AMPLIFIER
Ry Rp — AND
FEEDBACK
OHMS
NN CAL
у о”
427A-RC ` 7
Figure 4-3. Ohms Operation
COM
|= >—— — — —Ф
42T4—ROA V
AC RANGE AC POST
[VoLTs] ATTENUATOR ATTENUATOR ac
У A X DC / \
OQ} сео
2 2 AMPLIFIER METERING
3 $ $
© #—
Î l |
E IN T > 3
| FEEDBACK | <
$ AC FEEDBACK
400"
AZRI7 CAL
<
Figure 4-4, AC Operation
4-11. The AC Metering Circuitcontains both a feedback
stabilizedac amplifier andan averaging meter circuit,
The meter circuit converts the ac signal to a de volt-
age proportional to the average of the ac amplifier
output. A2R17 adjusts the current through the meter
so Lhat the scale reading is in rms volts.
4-12. CIRCUIT DESCRIPTIONS.
4-13. DC AMPLIFIER (Al).
4-14, Figure 6-3 is the schematic diagram of the
Model 427A. The input to the DC Amplifier (A1) is
applied through Pin 2 to the impedance converter
AlQ6. A field effect transistor is used as the impe-
dance converter because of its characteristically high
input impedance. Transistors A1Q7 and A1Q9 make
up a two-stage amplifier, with A1Q9 as an emitter
follower output stage. The signal from the emitter
of A1Q9 is fed back to the base of A1Q7 for gain sta-
bilization.
4-15. A1Q8 actsasa constant current source for A1Q6.
The constant current from AlQ8 assures linearity in
Al1Q6 and helps minimize drift.
4-2
4-16. DC OFFSET (A2).
4-17. The gate leakage from A1Q6 (Iggg) amounts to a
fraction of a nanoamp, This current is insignificant
with the input shorted; but with the input open, it flows
through the DC Range Attenuator resistanceof 10 M 2
resulting in a few millivolts deflection on the lower
ranges. Consequently, the meter indications with the
input open and with the input shorted can be different.
When measuring across a low impedance, Iggg flows
mostly through the low impedance; and this difference
does not effect the measurement. Unless Iaeg 15
compensated for, it will effect measurements made
across high impedances (>1 M 9).
4-18. The DC Offset Circuit (A2) (see Figure 4-5)
compensates for the leakage from A1Q6. A positive
voltage tapped from A2R7 reverse biases A2CR1. The
reverse leakage current from A2CR1 (IR) meets an
extremely high resistance at the gate of A1Q6 and
passes through the much lower resistance of the at-
tenuator, in a direction opposite to that of Iggg. By
adjusting A2R7, Ip can be set so that it and Icgg cancel
eachother. The net voltage dropacross the attenuator
01791-2
ME MA
„к
ED
ge «>
Model 427A
[70 A2
RE R7
= = = == = === = — — = — x =
(re Al TO ее |
OF AQT
A) =
RIO
I l
| |
Ic Gs 655
i |
1 1
< =
<, ОР ATTENUATOR
< (10 MEGOHMS)
J —6.75V
427A-B-0560
Figure 4-5, DC Offset Circuit
would then be zero. An alternative method of mini-
mizing the effects of IGss would beto zero the instru-
ment with the impedance of the measurement source
connected to the input terminals rather than with the
input shorted, A2CR1 has a temperature charac-
teristic quite similar to that of A1Q8. Therefore,
01791-2
Section IV
both Igas and Ig change by approximately the same
amount with temperature and the amount of additional
error at higher temperatures is lessened.
4-19. AC METERING CIRCUIT (A2).
4-20, Tigure 6-3 contains the schematic of the AC
Metering Circuit. The ac input from the ac post at-
tenuator is applied through A2C1 tothe base of A2Q1.
A2Q2 is an emitter follower that provides impedance
matching to common emitter output stage A2Q3.
Capacitor A2C4 provides an ac feedback path for gain
stabilization,
4-21. The output from the collector of A2Q3 is recti-
fied by A2CR3 and A2CR4 and applied to the meter
movement.
4-22, Resistor A2R17 is used to calibrate the ampli-
fier at low frequency and is adjusted for full scale
meter deflection witha 10 mV, 400 Hz input. Capacitor
A2C3 is used to calibrate the amplifier at high fre-
quency. With a 10 mV, 1 MHe input, A2C3 is adjusted
for full scale,
4-23. BATTERY REGULATOR Al (See Figure 6-3),
4-24. The Battery Repulator regulates the de voltage
fromthe 22.5 volt battery or from the optional power
supply. The voltage drop across AICR2 and the
emitter-base junction of A1Q3 provides the -6. 7 volt
reference for the power supply and the =6, 7 volt output,
A1Q5 senses changes in the +6, 7 volt output and con-
trois Al1Q2, the positive series regulator. Al1Ql is a
current source for Al1Q5, and diodes A1CR3, CRA4,
and CR5 provide temperature stabilization. Tran-
sistor A1Q4 provides a current shunt for A1CR2 to
Keep its voltage constant under heavy current loads,
4-3
Section V Model 427A
Table 5-1, Required Test Equipment
INSTRUMENT REQUIRED RECOMMENDED
TYPE CHARACTERISTICS USE MODEL
DC Voltage* Range: 0-300 V Performance Checks ~hp- Model 738BR Volt-
Standard Accuracy: 0.2% meter Calibrator
Test Oscillator*
Frequency Range: 10 Hz to 1 MHz
Output: 0 to 3 Vac
Performance Checks
-hp- Model 652A Oscil-
lator
Yariable Line
Transformer
Frequency Range: 50 to 60 Hz
Voltage Range: 0 {о 120 У
Performance Checks
Powerstat Type 116B
Decade Resistor
Range: 10% to 10 M&Q
Accuracy: +0.5%
Performance Checks
General Radio Model
1432Z Decade Resistor
Accuracy: +2%
DC Voltmeter Range: 0-50 Vdc Troubleshooting -hp- Model 427A Volt-
Accuracy: +2% meter
AC Voltmeter Range: 0-50 Vac Troubleshooting -hp- Model 427A Volt-
meter
Resistors
100 k + ‚ 1%
1 MQ +.1%
Performance Checks
-hp- Part No, 0811-0460
-hp- Part No, 0811-0473
* Contained in -hp- E02-738BR VTVM Calibration System
4#274-B-1180
VOLTMETER CALIBRATOR
hpT38BR
TEST OSCILLATOR
hpeaza
VOLTMETER CALIBRATION SYSTEM
hpEo2-7388R
® © Q
ee O © oQ 6
e Ia
® © = © фе
hp427A
VOLTMETER
5-0
Figure 5-1. AC Accuracy and Frequency Response Check
01791-2
A aN
Model 427A
Section V
SECTION V
MAINTENANCE
5-1. INTRODUCTION.
2-2. This section contains information necessary to
maintain the Model 427A. The following paragraphs
describe the Performance Checks, the Calibration
Procedures, and the Troubleshooting Procedures.
5-3. REQUIRED EQUIPMENT.
9-4. Table 5-1 is a list of the equipment needed to
properly maintain the Model 427A. If the recommended
model is not available, use any substitute that meets
the required characteristics.
5-5. PERFORMANCE CHECKS.
9-6, The Performance Checks are "in cabinet" tests
that compare the Model 427A with its specifications.
These procedures can be used both for incoming in-
spection and periodic inspection. A Performance
Check Test Cardis providedat the end of this section
for recording the performance of the Model 427A during
the performance checks, The card canbe removed
from the manual and used as a permanent record of
the incoming inspection or of a routine performance
check. If the Model 427A does not meet its specifi-
cations, refer tothe Adjustment and Calibration Pro-
cedures, Paragraph 5-25.
5-7. AC ACCURACY AND FREQUENCY RESPONSE
CHECK.
5-8. The AC Accuracy and Frequency Response Check
requires a test oscillator that is flat within + 0.5%
from 10 Hz to 1 MHz, The absolute value of the ap-
plied voltage must be accurate within +0.2%. The
-hp- Model T38BR Voltmeter Calibrator produces a
400 Hz signal that is within less than 0.2% of the in-
dicated output. The -hp-Model 652A Test Oscillator
can be adjusted to within less than0,25% of a desired
reference from 10 Hz to 10 MHz.
NOTE
Before beginning the Performance
Checks, be sure to adjust the me-
chanical meter zero according to
the steps in Paragraph 3-6,
5-8. AC ACCURACY CHECK.
D=10. Connect the test oscillator, and the voltmeter
calibrator as shown in Figure 5-1.
a. Set the voltmeter calibrator for an output of
0.01 volts at 400 Hz,
b, Set S1 in Figure 5-1 to position A.
c, Set the Model 427A FUNCTION to ACV and
the range to 0,01,
d. The 427A should read 0.01 volts rms + 2%
(2 minor scale division).
01791-3
e. Repeat steps a through d for each ac RANGE
selection through 300 V by setting the volt-
meter calibrator output tothe full scale value
for each range. The Model 427A indication
should not vary from the known inputby more
than 2% on any range. 2% corresponds to 2
minor divisions on the 0-1 scale and 1-1/2
minor divisions on the 0-3 scale.
f. Ser the Model 427A to the 1 volt range and
apply 0,9, 0,8, 0.7, 0,6, 0,5, 0,3, 0,2 and
0.1 volt signals. In each case the reading
should be within two minor divisions of the
known input signal.
E. Set the Model 427A to the 3 volt range and
apply 2.5, 2, 1.5, 1, and 0.5 volt signals.
In each case the reading should be within
1-1/2 minor divisions of the known input sig -
nal,
9-11. FREQUENCY RESPONSE CHECK.
9-12. The frequency range of the -hp- Model 652A
is 10 Hz to 10 MHz. The set level indicationmen-
tioned in the following steps is used to re-establish
the proper amplitude each time the frequency is
changed.
a. Set 81 in Figure 5-1 to position B. Set the
Model 427A RANGE to 0.01,
b, Set the test oscillator to 400 Hz and adjust
the output for a 0.95 indication on the 427A
0-1 scale.
с, Set test oscillator to expand, and adjust the
set level control (REF SET) for convenient
meter indication.
d. Record set level indication for use as a re-
ference in steps e and f.
e. Change the oscillator frequency to 10 Hz and
reget the oscillator amplitude to the set level
indication established in stepc. DO NOT re-
adjust the set level control on the oscillator.
The 427A Indication should not vary by more
than +2 minor scale divisions (+2%).
f. Repeat step e for 100 Hz, 1 kHz, 10 kHz,
100 kHz, 500 kHz and 1 MHz. In each case
the 427A indication should not vary by more
than +2 minor scale divisions (+ 2%).
5-13. Repeat Paragraph 5-11 with the 427A RANGE
set to 3 volts, and test oscillator output set to give
3 Y reading on 427A in step b. The 427A reading
should not vary by more than +2% (1-1/2 small
scale divisions),
5-1
Section V
5-14, RESISTANCE ACCURACY CHECK.
5=15, To check the resistance accuracy, precision
resistances are needed, Figure 5-2 shows the resis-
tance accuracy check using a General Radio Model
14327 Decade Resistor. The resistance used should
be accurate to within +0, 5% and should have a range
of 10 ohms to 10 M ohms,
a. With the input open, set the Model 427A
FUNCTION to OHMS and the RANGE to
X10. Adjust the DC ZERO/ wx adjustment
for an indication of « on the meter face,
(The needle should rest on the mark just to
the left of =).
b. Connect the decade resistor and the Model
427A as shown in Figure 5-2, and set the
decade for 10 £2.
с. The 427A meter should read within +5% of
the known resistance (- one small scale divi-
sion, + one-half small division).
d, Repeat steps a through c using the RANGE
and decade resistor settings listed in Table
5-2.
Model 427A
NOTE
The DC ZERO/ Qu adjustment
need only be made on the X10
and X1K ranges.
Table 5-2, Resistance Accuracy Check
RANGE DECADE
X100 100 2
X1K 1000 ©
X10K 10 KR
X100K 100 KR
X1M 1 MQ2
X10M 10 MQ
5-16, DC ACCURACY.
5-17. The DC Accuracy Check requires a dc voltage
standard that is accurate to within +0. 2% of its indi-
cated output from 0.1 volt to 300 Y. The -hp- Model
738BR Voltmeter Calibrator is accurate to within
+0, 1% of the indicated output, Figure 5-3 shows the
test setup for the DC Accuracy Check.
a. Set the Model 427A FUNCTION to +DCV and
the RANGE to 0.1,
DECADE RESISTOR
GENERAL RADIO 14327
hp 427A
VOLTMETER
PUDO
о
DO a
427A-B-0533
Figure 5-2. Resistance Accuracy Check
VOLTMETER CALIBRATOR
hp 738BR
9 O Q
pp)" *_ e68
hp 427A
VOLTMETER
4É7A-B-C550
Figure 5-3. DC Accuracy and Linearity Check
5-2
01791 -3
д ма
PO
ge —
~~ a
Model 427A
b. Adjust the DC ZERO/Qw= for zero, This ad-
justment need only be made onthe 0.1 volt
range,
C. Connect the voltmeter calibrator and the
Model 427A as shown in Figure 5-3,
d. Set the voltmeter calibrator output to 0.1
volts de. The Model 427A should read 0.1
volt +2%,
e. Repeat steps a through e for each RANGE
selection to 300 Y by setting the voltmeter
calibrator output to the full scale value for
each range. The Model 427A indication should
not vary from the known input by more than
+2% on any range. 2% corresponds to 2 min-
or divisions on the 0-1 scale and 1-1/2 minor
division on the 0-3 scale,
f. Set the de RANGE to 1000 Y and the voltmeter
calibrator to 300 V. The Model 427A should
read 300 Y +2% of full scale on the 1000 volt
range,
g. Set the Model 427A to the 1 volt range and
apply 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0,3, 0,2,
and 0.1 volt dc signals from the voltmeter
calibrator. 1n each case the reading should
be within two minor divisions of the known
input voltage.
h. Set the Model 427A to the 3 volt range and
apply 2.5, 2, 1,5, 1, and 0.5 volt dc signals.
In each case the reading should be within
1/2 minor division on the 0-3 scale,
i. Repeat setps a through f with the FUNCTION
set to -DCY and the voltmeter calibrator set
for a negative output. The test results should
be the same.
5-18. AC REJECTION CHECK.
5-19. A peak ac superimposed noise signal 100 times
the full scale input should affect the Model 427A read-
ing less than 1%. Figure 5-4 shows the test setup
using a variable line transformer as a noise generator.
А 7,07 volt rms output from the variable line trans-
former corresponds to a 10 volt peak noise signal.
The 10 volt noise signal will be applied to the 0.1 volt
dc range.
Section Y
a, Set the 427A FUNCTION to +DCV and short
the input. Set the RANGE to 0.1 and adjust
the DC ZERO/Q« for 0 meter indication.
b. Switch the FUNCTION to ACV and the RANGE
to 10, Connect the variable line transform-
er and the Model 427A as shown in Figure 5-4.
¢. Adjust the transformer output for a reading
of 7, 07 volts rms on the 427A,
d. Switch the 427A FUNCTION to +DCV andthe
RANGE to 0.1,
e. The meter reading shouldbe 0 +1%(1 minor
scale division).
NOTE
The meter may move upscale
momentarily and then return to
zero. This indicatesthe charging
of the DC Filter capacitors and
is normal,
Í. Repeat steps a through e using the 1 volt dc
range and 70, 7 volt rms signal from thetrans-
foriner.
5-20, INPUT IMPEDANCE CHECK.
5-21. INPUT RESISTANCE CHECK.
5-22. Figure 5-5 shows the setup for the input resis-
tance check, A 1 M{ resistor is connected in series
with the input, and the voltage drop across the input
resistance will be:
Rin
Er = Eapplied | Rgeries + Rin
With 1 volt applied, En will be 0, 91 volt if the input
resistance is 10 M{2. Ep varies directly with changes
in Rin.
a, Connect the Model 427A and the voltmeter
calibrator to position A illustrated in Figure
5-5. Set the Model 427A FUNCTION to+DCV
and RANGE to 1 V.
b. Set the voltmeter calibrator for +1 V output.
C, Connect the voltmeter calibrator to position
B shown in Figure 5-5.
VARIABLE
LINE
TRANSFORMER
hp 427A
VOLTMETER
A2TA =E= CAL
Figure 5-4. AC Rejection Check
01791-3
5-3
Section V Model 427A
hp 427A
TEST OSCILLATOR VOLTMETER
hp652A pr
TUN
—
© @ 3
® © = © geo 100K ,0el% | TO m
[ hpo811- 0460
St ®
INPUT CAPACITANCE CHECK
VOLTMETER CALIBRATOR
hp7388R hp427A
VOLTMETER
ATTN
e Q @
ops °° 008 oes
= E) mm
\ +
3
| | MES, Cal
No hp 0811-0473
A AE BA
INPUT RESISTANCE CHECK
Figure 5-5. Input Impedance Check
d. The voltmeter reading should drop to 0. 91,
indicating an input resistance of 10 M£, The
input resistance may vary slightly, and a
tolerance of +2% should be allowed.
5-23, INPUT CAPACITANCE CHECK.
5-24. The 10 MR input resistance is shunted with 40
pF on the 0.01 through 1 volt ac ranges and with 20 pF
on the 3 through 300 volt ac ranges. For this input
capacitance check a 100 kf resistor is placed in ser-
ies with the meter input, At a known frequency, the
reactance of the shunt capacitance will be equal to
100 kQ. At this point the voltage across the input re-
sistance and shunt capacitance will be equal to 0. 707
times the input voltage. The input capacitance may
be checked by finding the frequency at which the dis-
played voltage drops to 0, 707 times the input, As in-
put capacitance decreases, the roll off frequency in-
creases, and vice versa.
a. Connect oscillator and Model 427A to position
A of the input capacitance check (Figure 5-5}, and set
the Model 427A FUNCTION to ACV and RANGE to 1V.
b. Set the oscillator frequency to 60 Hz and ad-
just the amplitude for a full scale display on
the Model 427A.
e. Connect the oscillator to position B and in-
crease the frequency until the meter display
drops to 0.707. The frequency at this point
should be about 40 kHz. The input capacitance
is nominally specified at 40 pF and may vary
from instrument to instrument. A frequency
variation of +10% is acceptable.
d. Repeat stepsathroughc usingthe 3 volt range
of the 427A. Increase the frequency in step
c until the reading drops to 2.1 volts. This
should occur at about 80 kHz. This verifies
input capacitance of 20 pF on 3 volt range and
above.
ADJUSTMENT AND CALIBRATION
PROCEDURES.
5-23.
5.26. The following adjustment and calibration pro-
cedures should be used only if it has been determined
through the performance checks in Paragraphs 5-5
through 5-24 that the Model 427A is not performing
within its specifications. The location of the internal
adjustments is shown in Figures 5-6 and 6-2,
5-27. COVER REMOVAL.
5-28, To remove the top or bottom covers, remove
the Phillips screws securing the cover, slide the
cover about 1 inch to the rear, and lift it off. To re-
place the cover, reverse the removal procedure.
5-29, To remove a side cover, remove the four Phillips
screws and lift it off.
01791-3
æ |
Y ‘a, Model 427A Section V
AZC3 A?Ri7 AZRT A?RE5 A2R4 AIRIS AIR20 AIRIS AIRS
"N rns °C i SET > CAL DE CAL OHMS CAL oHMSCAL -— AMPBAL RES ADI
gr и A
NY Jeoo pogós 225 DOO Nahoo/00078
ON O O
O Dé) | © der O 3 № ® 0 DO
59 © О 16 @ 90
OO re (@ © О DO |
OO \ O O —— —O 5
JO O 5 O OQ
OO О = = O OO
OU O O DO
O OL JO Ol JOO
DO ЗОО ООО ООО 290 0000000500
| 090 Obed Elo о
LEFT SIDE \ 7 RIGHT SIDE
A2R3 C3
AV SV
DC CAL IOOKC ADJ
Figure 5-6. Location of Internal Adjustments
NOTE
Before beginning the calibration, be
sure to adjust the mechanical meter
zero according to the steps in Para-
graph 3-6.
b, Short VOLTS to COM and OHMS to COM. Set
FUNCTION to +DCY. Meter should be zcro-
ed within 2 minor divisions upscale,
C. Switch FUNCTION to OHMS. If meter deflects,
adjust AIRS REG ADJ [or zero deflection.
This may affect +DCV zero setting, so rotate
FUNCTION back and forth between OHMS and
+DCY, and adjust A1R5 until meter reading
is the same in both positions,
5-30. AMPLIFIER BALANCE AND ZERO OFFSET
ADJUSTMENT,
a. Short VOLTSand COM terminals: set FUNC-
TION to either +DCV or -DCV.
b. Set DC ZERO/Qw for zero deflection.
с, Remove shorting connection from VOLTS and
9-32, AC CALIBRATION.
5-33. Three adjustments must be made to calibrate
(E «=.
a
COM terminals. If meter deflects, adjust
A2R7 OFF ADJ for zero deflection. Short
VOLTS and COM terminals and recheck zero
adjustment. Repeat steps band cif necessary.
d. Set the FUNCTION to +DCV and turnDC ZERO/
So fully to the right. Set Range to 0.1. Re-
cord position of indicator.
e. Turn FUNCTION to -DCV and rotate DC
ZERO/2 fully to the left. Note meter
indication,
f. Repeat steps d and e and adjust A1R15 AMP
BAL until the meter indication in both steps
is the same.
NOTE
If the range of adjustment A1R15 is
insufficient, refer to Paragraph 5-74.
5-31, REGULATOR ADJUST.
a. Complete Amplifier Balance and Offset adjust-
ment (Paragraph 5-30),
01791-2
the ac circuits in the Model 427A. First, A2R17 ad-
justs the absolute amplitude calibration with a 10 mV
400 Hz input. Then A2C3 is adjusted with a 10 mV 1
MHz input to calibrate the high frequency response.
Finally the frequency response of the AC Range At-
tenuator is set by adjusting C3 with a 3 V 100 kHz
signal applied to the input,
5-34. LOW FREQUENCY CALIBRATION.
a, Connect the Model 427A as shown in Figure
9-1, and set S1 to position A.
b. Set the voltmeter calibrator output to 400 Hz
at 0,01 volt rms, and set the 427A RANGE
to 0.01 and FUNCTION to ACV.
c. Adjust A2R17 400 CPS ADJ for exactly 0.01
volt indication on the 427A. If the range of
adjustment A2R17 is insufficient, refer to
Paragraph 5-81.
0-35. HIGH FREQUENCY CALIBRATION,
a. Connect the Model 427A ag shown in Figure 5-1.
9-5
Section V
Set S1 to position B. Set 427A RANGE to
0,01 and FUNCTION to ACV.
b. Set the oscillator to 400 Hz and adjust the
output for exactly a 0.01 volt indication on
the 427A.
е. Adjust the set level control (REF SET) on
Test Oscillator for a convenient meter indi-
cation. Record set level indication for use
as a reference in step d.
d. Adjust oscillator frequency to 1 MHz and
adjust the amplitude vernier to the set level
indication established in step c. DO NOT
readjust the set level control.
e. Adjust A2C3 1 MC ADJ for exactly a 0.01
volt indication un the Model 427A. If the
range of adjustment A2C3 is insufficient,
refer to Paragraph 5-76.
fi, Rotate 427A RANGE switch to 3, set Sl to
position A. Adjust the voltmeter calibrator
for an output of 3 V at 400 Hz and record
indication on 427A meter.
g. Change S1 to position B. Set the oscillator
to 400 Hz, and adjust amplitude for 427A
meter indication recorded in step I.
h. Adjust the set level control (REF SET) for
a convenient reference.
ii Increase oscillator frequency to 100 kHz,
and readjust oscillator amplitude to set level
reference established in step h.
ji. Adjust C3 3 V 100 kHz ADJ for exactly a3
volt indication on the 427A.
5-36. RESISTANCE INFINITY ADJUSTMENT.
5-37. The resistance calibration is affected by the
amplifier balance, zero offset, and regulator adjust-
ments. Perform the steps in Paragraph 5-30 and
5-31 before making the resistance infinity adjustment.
a, Set FUNCTION to OHMS and RANGE to X10.
b. Short OHMSto COM and adjust the DC ZERO/
Qu for zero indication. Open the input and
adjust A1R18 X10 OHMS CAL for an æ indi-
cation, The indicator should rest on the
mark just to the left of =.
ce Change RANGE to X1K, short OHMSto COM
ard adjust DC ZERO/ Q« for zero indication,
Open the input and adjust A1R20 X1K OHMS
CAL for an « indication,
5-38. DC CALIBRATION.
5-39. A dc voltage standard is needed to calibrate the
de ranges. A2R3, A2R4, and A2R5 are adjusted for
5-6
Model 427A
full scale inputs onthe 0.1, 0.3, and 1 volt ranges
respectively. The 3 volt through 1000 volt ranges
are calibrated by A2R5 and require no special cali-
bration. Use the test setup in Figure 5-3.
a Set FUNCTION to +DCV and RANGE to 0. 1.
Set the voltmeter calibrator output to +0, 1
volt,
b. Adjust A2R3 0.1V DC CAL for full scale on
the 0-1 scale.
c. Rotate RANGE to 0.3, and change the cali-
brator output to +0. 3 volt,
d. Adjust A2R4 0.3V DC CAL for 3 on the 0-3
scale,
e, Rotate RANGE to 1 and change the calibrator
output to 1 volt.
f, Adjust A2R5 1V DC CAL for full scaleonthe
0-1 scale.
5-40. ALTERNATE PERFORMANCE CHECKS
AND CALIBRATION PROCEDURES.
5-41, The following alternate procedures should be
used only if the equipment in Table 5-1 is not avail-
able. In each alternate procedure use an instrument
of the specified accuracy. If a less accurate instru-
ment is used, the calibration or test may not be within
the Model 427A specifications, To guarantee a specific
accuracy, use a standard at least four times more
accurate than the Model 427 À.
5-42, AC CIRCUITS.
5-43. Any test oscillator with low distortion (<2%)
may be used as an ac voltage standard. If the distor-
tion level is too high, the calibration may be wrong,
as the 427A is an average responding rms calibrated
meter. (The effects of harmonic distortion are dis-
cussed in more detail in Section II, Paragraphs 3-14
and 3-15.)
5-44. Monitor the oscillator output with a recently
calibrated rms voltmeter known to be four times as
accurate as the Model 427A over the same band of
frequencies. The rms voltmeter serves as a refer-
ence. Each time the oscillator frequency is changed,
readjust the output for the reference. The Model 427A
ac calibration is based on a 400 Hz absolute refer-
ence, so always start the ac calibration or perform-
ance checks at 400 Hz,
5-45, RESISTANCE CIRCUITS.
5.46, If a decade resistor is not available, a selec-
tion of precision resistors may be used. The resistors
should be at least 1% resistors and the values selected
should correspond to the RANGE settings, The -hp-
part numbers for 1% resistors for each range are
given in Table 5-3,
01791-3
e a
- ">
Model 427A
Table 5-3. 1% Resistors
RESISTOR (+1%) -hp- PART NO.
109 0757-0984
1002 0757-0198
ko 0757-0159
10k0 0757-0839
100k Q 0757-0367
1M 0698-3583
10MO 0698-3592
5-47. DC CIRCUITS.
5-48. A precision dc voltage source is required for
de calibration and performance checks, Since the
427A is only calibrated on the 1 volt, 0,3 volt and 0.1
volt ranges, only three different voltages are needed.
5-49. A mercury battery has good short term stability.
Connect a series voltage divider with a variable output
across the battery and monitor the output witha recently
calibrated ас voltmeter knownto be four times as accur-
ate as the Model 427A, Use this output to calibrate
the 0,1, 0.3, and 1 volt ranges.
5-50. AC REJECTION.
5-51. To check AC Rejection on 0.1 volt range an
oscillator with output of 10 volt peak-to-peak into 10
M ohms may be used, If the -hp- Model 738BR Volt-
meter Calibrator is available a 400 Hz 10 volt peak-
to-peak output may also be used to check the AC Re-
jection of Model 427A.
5-52, INPUT IMPEDANCE CHECK.
5-53. Measure the resistance betweenthe VOLTS and
COM terminalsdirectly with the Model 427A Function
Switchat +DCV or -DCV using an accurate ohmmeter.
Another Model 427A could be used for this purpose.
If an L-C meter or capacitance bridge is available,
measure the input capacitance between the VOLTS
and COM terminalsdirectly, Be sure the Model 427A
FUNCTION switch is in the ACV position.
5-54. BATTERY REPLACEMENT.
5-55. Figure 5~7 showsthe battery holder and the bat-
tery connectlons, Turnthe twist-lock fastener 1/4 turn
counterclockwise, tiltthe battery and holder toward the
rear of the instrument, and lift out. Replacethe battery
with an Eveready 763 or RCA VS102,22 1/2 volt dry cell
DN
>
LY
42TA-B-05654 В
Figure 5-7, Battery Replacement
01791-3
>
Section Y
5-56. TROUBLESHOOTING.
5-57, Whenthe Model 427A operates improperly, first
adjust and calibrate it according to the procedures in
Paragraph 5-25, If calibration is impossible, then
proceed with the troubleshooting steps,
5-58, Check the instrument for obvious evidence of
trouble, such as loose or broken wires or broken
connectors. Check the printed circuit boards for
cracks and separations, and ensure that all connectors
and pins are clean and tight,
5-59, Isolate thetrouble to a particular circuit using
the troubleshooting table (Table 5-4) and the Theory
of Operation (Section IV). Then refer to the Trouble-
shooting steps for that circuit in the following para-
graphs.
Table 5-4, Troubleshooting
SYMPTOM
PROBABLE TROUBLE
AREA
Battery ok, no re-
sponse to input.
Power Supply. (See
Paragraph 5-80. )
All +DCV ranges pegged
with no input. ACV and
OHMS ok.
DC offset circuit, Check
A2CRI1. Thencheck
A1Q6.
Nonlinear tracking on
voltage ranges.
DC Amplifier. Check
AlQ8 and associated
circuit. Check value
of range resistors.
Check AIR14 and A1Q9.
Constant upscale deflec-
tion on lower +DCV
Tanges; voltage at TP1
low.
DC Amplifier. (See
Paragraph 5-63.)
Meter pegs on +DCV
and OHMS ranges,
DC Amplifier; check
A1Q6, A1Q8, and A1Q9.
(See Paragraph 5-65.)
OHMS range always
reads near zero, DCV
and ACV ok.
Range resistor (Ry in
Figure 4-3) open.
Check R19 through
R25 on S1.
Range resistors (Ry, in
Figure 4-3) shorted.
Check R12 throughR18
on Si.
Check Power Supply.
OHMS always reads =.
DCV and ACV ok.
Either one of R19
through R25 (Rg) shorted
or one of R12 through R18
open.
Intermittent operation. Power supply, check Á1-
Q4 (See Paragraph 5-60. )
Zero-offset in ACV AC Metering Circuit
СТМ greater than
2 +
(See Paragraph 5-67.)
Meter pegs full scale
on any AC range,
AC Metering Circuit,
check A2CR3 and A2CR4
(See Paragraph 5-67.)
=
Section V
5-60, POWER SUPPLY.
5-81. Check at Al pin 7 for +6. 4 to +7 volts and Al
pin 9 for -6.4 to -7 volts. If there is no output, check
A1Q4 first. If the power supply has been overloaded,
A1Q4 may be bad. Minimum battery voltage is 15.5
volts.
5-62, Measure the dc voltages at the check points
given in Table 5-5, All measurements are made with
reference to circuit ground.
Table 5-5. Power Supply Voltages
NOTE
The voltages listed in this table
are nominal. A tolerance of
+10% should be allowed except
for minimum voltages listed.
CHECK POINT VOLTAGE
+15V (+8V min)
+7, 3V
+14,8V (7.8V min)
+6. 7V (+6.4V min)
+15V (8, 6V min)
Emitter A1Q1
Collector Al1Q1
Base A1Q1
Emitter Al1Q2
Collector A1Q2
Emitter A1Q3 -0, DY
Collector A1Q3 -0.2V
Collector AlQ4 -6.7V («6;4V min)
Base A195 +0, 5V
Across A1CR2 +6.2V
5-63. DC AMPLIFIER.
5-64. To make an operational check of the DC Ampli-
fier, set the RANGE switch to 1 and the FUNCTION
switehto+DCVY. Connectal volt sourcetothe VOLTS
and COM terminals and monitor the voltage at Al pin
8. Since the DC Amplifier is a unity gain amplifier,
the voltage should be +1,07 0,07 volts dc. If this
reading is correct, the DC Amplifier is operating
properly. If it is incorrect, proceed with the follow-
ing troubleshooting procedures.
5-65, Check at the colleetor of Al1Q9 for +3,5 Vdc,
and check for +3.0 Vdc at AITPI. If the voltage at
the collector of A1Q9 is quite high (6 or 7 volts) and
the voltage at A1TP1 is +3,0 Vdc, AlQD is probably
open, If the collector voltage is low and the test
point voltage is correct, AlQ8 is probably shorted.
If both voltages are incorrect, À1Q7 or A1Q8 is probably
bad.
5-66. If the collector voltage on A1GO is correct and
the voltage at A1TP1 is slightly higher than normal,
A1Q86 is probably bad.
NOTE
If A1Q6 is replaced and the meter
remains pegged or indicatesupscale
and cannot be adjusted, check the
value of factory selected component
A1R19 See Paragraph 5-71 and 5-73,
5-8,
Model 427A
5-67, AC METERING CIRCUIT.
5-68. To check the AC Metering Circuit, set the
RANGE to 0,01 and the FUNCTION to ACV. Connect
a 10 mV rms source to the VOLTS and COM terminals
and monitor the signal at A2 pin 0. The signal at A2
pin 0 should be 10.7 mV rma +0.7 mV. If the mea-
sured signal is incorrect, the trouble is in either the
DC Amplifier or the AC Post Attenuator.
5-69, Monitor the signa! at the collector of A2QS.
The signal should be 0.28 Vrms +0. 04 \. I the
measured signal is correct, the AC Metering Circuit
is functioning properly. If not, proceed with the
following troubleshooting procedures.
5-70. Check for dc voltage levels listed in Table 5-6.
If a given reading is wrong, the trouble is probably
in that component or its associated circuit. If A2CR3
or A2CR4 are replaced and the zero offset in ACV
FUNCTION is greater than 2%, checkthe value of factory
selected component A2R14*, See Paragraph 5-72 and 5-77.
Table 5-6. AC Metering Circuit Voltages
NOTE
The voltages listed in this table
are nominal. A tolerance of +10%
should be allowed.
CHECK POINT VOLTAGE
A2TP1 +2.8V
A2Q1 Collector +2.8 V
A2Q2 Emitter +2,2 Y
A2Q3 Collector -0,5 V
5-71. ADJUSTMENT OF FACTORY SELECTED
COMPONENTS.
5-72, Certain components within the Model 427A are
individually selected in order to compensate for
slightly varying circuit parameters. These compo-
nents are dencted by an asterisk (*) on the schematic,
and the optimum or average value is shown. The
following paragraphs describe the function of each
factory selected component and give instructions for
their selection. Normally these components do not
need to be changed unless another associated compo-
nent is changed. For example, replacement of a
transistor may require the changing of an associated
factory selected component.
5-73. A1R19*,
5-74. A1R19* adjusts the range of the AMP BAL re-
sistor A1R15. If the AMP BAL A1R15 cannot be ad-
justed properly after replacing transistor A1Q6, Al-
R19* may need to be changed. Use the following steps
to select A1R19*,
a. Set RANGE to 0. 3.
b. Set DC ZERO/Q« adjustment to center and
A1R15 to its center.
01791-3
„д <a
‚>
a ">
Model 427A
c. Select the FUNCTION (+DCV or -DCV) which
will produce an upscale deflection.
d. If the FUNCTION selected is -DCV, increase
the value of A1R19*; if +DCY is selected, de-
crease AIRI9*, The value range of AIR19*
is 0 to 18508,
5-75. A2C2*,
5-76. A2C2* adjusts the range of the high frequency
calibration capacitor A2C3 1 MC ADJ. If during the
high frequency calibration (Paragraph 5-35) A2C3 can-
not be adjusted for the proper reading, the value of
A2C2* should be changed. ifthe reading is consistently
high, change the value of A2C2* to 47 pF. I the read-
ing is consistently low, remove A2C2*.
5-77, A2R14*,
5-78. A2R14* is factory selected to improve upscale
meter tracking and correct any non-linearity of diodes
A2CR3 and A2CR4. If diode A2CR3 or A2CR4 are re-
placed, A2R14* may need to be changed. Use the pro-
cedure outlined in the following paragraph to select
A2R14*,
5-79, If a zero-offset greater than 2% (two minor
divisions on the 0-1 scale) exists in ACV FUNCTION
replace A2R14* with a smaller value of resistance.
The correct value for A2R14* is the largest value of
resistance that adjusts the zero-offsetto less than 2%.
Tracking error could result if the zero-offset indica-
tion is reduced below 1%. The nominal value for
A2R14* is 91 ohms (-hp- Part No, 0683-9105), The
recommended replacement value for A2R14* is either
a 47 ohm (-hp- Part No. 0683-4705) or 68 ohm (-hp-
Part No. 0683-6805) 1/4 W, 5% resistor.
5-80. AZ2R16*.
5-81. A2R16* adjusts the range of the low frequency
Calibration Resistor A2R17 400 CPS ADJ. If the AC
Metering Circuit is functioning properly and the 400
CPS ADJ cannot be adjusted for the proper indication,
during low frequency calibration (Paragraph 5-34),
A2R16* may need to be changed. I the reading is
consistently low, change A2R16* to 56,2 ohms (-hp-
Part No, 0757-0395).
01791-2
Section Y
5-82. ETCHED CIRCUIT BOARD REPAIR.
0-83. The Model 4274 uses plated-through double-
sided etched circuit boards, To prevent damage to
the circuit board and components, observe the follow-
ing rules when soldering:
a. Wear clean, lintfree cotton or rubber gloves
when handling the circuit boards. Avoid
touching the board or components with bare
fingers as skin oils can cause leakage paths.
b. Use a low-heat (25 to 50 watts) small-tip
soldering iron, and a small diameter rosin
core solder.
c To remove a component, clip a heat sink
(long nose pliers, commercial heat sink
tweezers etc.) onthe component lead as close
to the component as possible. Place the
soldering iron directly on the component lead
and pull up on the lead, If a component is
obviously damaged or faulty, clip the leads
close to the components and then remove
the leads from the board.
A
ECAUTION}
A
EXCESSIVE OR PROLONGED HEAT
CAN LIFT THE CIRCUIT FOIL FROM
THE BOARD OR CAUSE DAMAGE
TO COMPONENTS.
d. Cleanthe component lead holes by heatingthe
solder in the hole, quickly removing the g0l-
dering iron, and inserting a pointed, non-
metallic object such as a toothpick.
e, To mount a new component, shape the leads
and insert them in the holes. Clip a heat sink
on the component, heat with the soldering
iron, and add solder as necessary to obtain
a good electrical connection.
f. Clipexcessleads off after soldering and clean
excess flux from the connection and adjoining
area, using type TF Freon (-hp- Part No,
8500-0232).
5-9
UN
“о неф | > mu 2° {0
a,
ae,
« sjuaucdwic) Ч23145 JO UOIJEIOT ‘1-9 2andtg
ca
+
+ ‘SHIAVM YJHLO WOY4 HJ4JI0 SHZEWNN Nid VIS MOST ENE
= | NOILINDA]) zi
a [№154] INFWNYLSNI 50
= 1NOH{ MOLLOS HQOYHJ O3MGIA JIT SHAATM HILIMS
Z 12 0Z 61 ¿1 Y SI bi El ZI 1 0 6 8 2 9% 6 $ € | 22 12 02 El ¿1 SI Sl # El 2 1 0 56 8 2 9 6 b € 2 |
TENINHAL
[647104] Ге
AY
Об
uo:
Sr6
aL
у I
Ta
I T
€5
€
1 T
+ r
20€
PE
e
q TI I
Lent 56 J 06 * GbE 76 EE
¿76 19 |
| r Zid
| 926"
| 3 ZE
906
Cae /208 /T06 Jk:
CT
A
8
B
L
a нь a
176 — : | z =
£06 a 8 16 £ | in ol £
#0 6 l : | | ! 6 26
FZ6 a I ное) + 6 I v6
106 O, 9 с и 8 =
ROE —0 AOS HOTOS TIT YALIN Live ` ¿
a? al a | "a el 9 #6
= (AVHO ‘HAOUE Вы El 5 ve
ET Го z care Bao
> b LIAM = 16 53) "EJOS b 216
SIG Ps | MOTOO OHVONY.LS DNIEN € 906
E 106 UCIOS HIM SALONEC IG — — I о!
© © l TE | с
= 20€ | SALON EA, ¿eu OL
3 Ce av) LT
on y - ki
01791-2
6-2
LE
DC ZERO/Nc0 A2
R20
XI F
“RD (e) О, WHT/BLK/ORN
2 RS ARC} os WHT/BLK/YEL
GRN
> NR O
(8)
O OFF || WHT/RED/ VIO
ADJ
WHT/ELK/BLU 3(0) ais “CRIT > OF: WHT/ RED YEL
Ta LRG (6) 7 WHT/BLK/BRN
aa
AMP 3
AN ® BAL ca OF { WHT/BLK/GRN
— 4 |-- 12 : i . -
WHT/BRN/YEL [email protected] NO: _- (0)5 WHT/RED/GRN
WHT/YEL/GRY &(®) A ERA (6)4 wHT/BRN/BLU
| i BLu OS ul
WHT/RED 7(8) a
WHT/YEL B(®)
{RIA @ 3 WHT/BRN/GAN
wur wie] 9(@) (5) o нтв кумо
| REG qa ARS © !
mejo) ADJ RIÓ (®) | (WHT/BLK/RED
WHT/RED/GRY li(e) —|R3 - HB.» ca @ ® (6)O WHT/GRN/VIO
О =O M&S св О
Ce {es REY
=
: CRS \ — 3
un cr
8 CRT | © ;
n R22 i =
| `
ANY PC PLUG ON BOARDS ARE FOR FACTORY TEST ONLY. NUMBERS BY STAND-OFF
PINS APPEAR ON SCHEMATICS.
Si A!
5
о
o
R37 C3
MI
AZ TA A-05404
ORN WHT/BLU/YEL WHT/BLK
TO TO TO
[voLTs]
Figure 6-2. Component Location
10,
mM ес
mi .-1 ¡a
| rr
4
dl
ONLY
19,
Об, ОЙ TT BT m PPE. 1 и = ло
SCHEMATIC NOTES
PARTIAL REFERENCE DESIGNATIONS ARE SHOWN. PREFIX
WITH ASSEMBLY OR SUBASSEMBILY DESIGNATION(S) OR BOTH
FOR COMPLETE DESIGNATION.
COMPONENT VALUES ARE SHOWN AS FOLLOWS UNLESS OTHER-
WISE NOTED.
RESISTANCE IN OHMS
CAPACITANCE IN MICROFARADS
CONNECTED TO "A" IN OPTION 01 INSTRUMENT; CONNECTED
TO "B" IN STANDARD INSTRUMENT.
DENOTES ASSEMBLY.
-—— — — — — — DENOTES OPTION 01.
DENOTES MAIN SIGNAL PATH.
DENOTES DC FEEDBACK PATH.
DENOTES AC FEEDBACK PATH.
Ll DENOTES POWER LINE GROUND; VOLTMETER CHASSIS,
V DENOTES SIGNAL GROUND; CIRCUIT GROUND.
[ — ]PENOTES FRONT PANEL MARKING,
L _]DENOTES REAR PANEL MARKING,
y= DENOTES SCREWDRIVER ADJUST.
Xx AVERAGE VALUE SHOWN, OPTIMUM VALUE SELECTED
AT FACTORY.
ONAN DENOTES COMPONENTS NOT MOUNTED
ON ASSEMBLY.
J24 DENOTES WIRE COLOR: COLOR CODE SAME AS
RESISTOR COLOR CODE. FIRST NUMBER IDENTIFIES
BASE COLOR, SECOND NUMBER IDENTIFIES WIDER
STRIP, THIRD NUMBER IDENTIFIES NARROWER STRIP.
(e. E. 924, = WHITE, RED, YELLOW.)
OHMS RANGE
# ATTENUATOR À 906
DE
©,
O,
R25
| том
R24 ?
[582K 7
R23 5
GAL (©) ®
EDO {5} ° ©
| 3
R21
18750 @ ©
2
675 o” ©
20
Lao Me
F/0 $67.5м QD) SIF(F,R)
S2A(R) 945 hs | 945, |
15
Dus]
o 2 RIZ
20, SIE(F,A)
73M @,
© бе (3)
[= 0cv] 4
— 0 101-6 o
348, | 9
ОНМ5 | > — «€ RIS
7 ита @
ACY 1
RIG 12
2! | 1.75K (6)
RIT 4
Leek <)
18
co 1.295
COM 30, Cul 4 2
A у ©
O,
®,
DC RANGE
VOLTS) > —— $e RI
J [BATT] 10K O SIBIFA) o SIDR} (D
i e RIS RE 1,9
[+ Dev] ©.
© + QU
Hoo
©
° es
net
9 6.837MÉ ©,
RS _ 3
2.163M: {7
R42 5
683.7K;
216 3«® ©
68.37K$ do
RL и
= Ka
21.63K2 D
RG 12
10K 2
\
AC RANGE
f ATTENUATOR À
e
o {Dy SIAR) ‚95, |
3 в n
у ® в
ca < RIO в
кс -7-3PF À Fiom O,
ADJ | o 8
®
e,
,
La [an
PET £3l723K | ©
©
om
A2TA-J-1ITDA V
J <= — tp parie ie . - в hem me " a
OHMS RANGE
F ATTENUATOR À 228,
©,
O, [FUNCTION]
+6.7V SZE(F) RY
©, FROM —o— о
7.5M RANGE AT
© ©
O4
eek (7) XIOK |
A23 5 G) xIK | IO XiDOK | —
676K © , 4
3 @ woo 3 i _—30 км © 226,
TE 1
eso © @ xo . “00 xiom (Y O 307,
| “ый
6750 = @ ,. 03 E —300 © less
RZO 22 ONLY [ ос —
575 OQ © -al 1000 —oncy 4 = -
©. Praz]
о
< RI9
267.58 (D) __ SIFIFA)
sas o DC OFFSET sek DS ——
233 245, OHMS ! yon c# CR] I 227,
- ]
REI RE
2 RIE © ZOK
prove 2, SIE(F,R} а
[10.5 O —— — —Y- - P/0 À | | DC AMPL
(Ole: ° =
pn, FUNCTION |
T RE 12 (E) OHMS ®
ик © a 2
o (D) — Le
RI7 14 Dev ! 2
| 18.8 7 © “+N 2 : J
| 8 y. 2
1, 295M ey MS o |
J 18 (A) OFF J "O
®, о
e, ©
I
©
DC RANGE oa] |
f ATTENUATOR Y CONTO
[FUNCTION] pe FILTER
. re a as
¡OK (1) SIB(F,R) Ke) SIDR) (1) DC (A) S2CIR) 3, i ERR SA ak 453k _ (By S2C(F) 334, D ЗНА} 977, (a) SPDIR) 5 2
3 E RE 1,8 83, 7 © 3 ват 5 8 “ RIO
| ou où o ROM 2 2800
lo © Ka 1 © le:
® © e ©,
С -——— E = = HZ
RIA 13 13
O. ® 245) ©. © 5 !
e „723 a" 20 18 3 © |5 1
$ 9 E. ®, © ©, ©, ASSEMBLY
‚неба а o ? © "чение
$83 SE ©. o | 967, M {A S2DIF) 256 lo EL
216 Ro ue > Te’ — o
OT вс? 9 >. " +
60.37K2
ино 224 ©, LO,
21.63K5 {ny an O, 07
RA < ! Il [4 à
10k%
©,
ac A ©
RANGE ‘в
y ATTENUATOR \
— <= AC
+ BAT,
TO
lo R356 MI
3 SEE T
4 A FOR E
| LEVEL
Ar
— BAT.
TO
R36 EMI
4:11
+3 TERK
©
|
|
|
|
|
|
|
PWR SUP, 7
YIA S2E(RIIO
Po A2 | AC METERING CIRCUIT A
SSEMBLY (00427-
Fro Al | DC AMPLIFIER & BATTERY REGULATOR ASSEMBLY (00427-66501) _
0
! DC AMPLIFIER FROM — 9-0 ®
y I AI-S 10 20% |
X : O € +647V
O ASSEMBLY
6 MOUNTING
| o SCREW
I
| © IT
I
E == ke gay
+3 Les
I o
I т -
IMPEDANCE € 4 |
CONVERTER — ¡[DE ZERO/AS0] 4 8.1, DC/OHMS
, —— y A
CTION] 96 | 8 AC POST
a } RI
2800 t
R3I
| ле 28 on © OF, 95 geod
as: aa
1 / 2271 RI ©,
I 2
10813 619 @
ASSEMBLY t R28$ mas $
РИО ' 3541.94 _ 909 3)
SCREW AA o |
R29£ R34 7
108.17 1020 3 !
АЛЛА, =
‚ RIOS 9
50: ©
) Vv |
BATTERY REGULATOR \ f | ©,
3 {
1
RI o +5:7 Y 5
3 Ponle cy || es |
R2 SeEíFIS 7 TT
560 ©
——————]
ва © ?
al 30.IK$ l an o
| I
в
+ Ват.
R35 B MI R4 à y cR3 !
SEE TABLE 5-5 12.lk: |
FOR DC VOLTGE
| LEVELS. ME CRA
N |
Е 93 hz2 Y CAS
e:
CRE 33542 =6+47V
6+2V 97 ~ BTV
1! 10 x * + : SL To
Le $ ow La S2C{RIIO
RS REG ADJ 5
— ВАТ, 5
BAT, 7.
R38 aM
COPYRIGHT 1966 BY HEWLETT-PACKARD COMPANY
AC METERING
+É
01
ha
o
a
Model 427A Section V
во Аг |
|
(A) SEBIF) BL, !
+ ВАТ, R33
FROM 158K === СА ===, [RANGE]
via Socio © 7 "© PWR SUP, | | D SIC
5 20 I > I Fig
RO; [FUNCTION] К O,
Li 22 Р/О cw RI
— © o o SX A 3 500 10 y 20%
14
2 0 ors TTR yl
14 3 21 CW R4 RI 16
© 1500 2 go
215, 216 * "7" Í
> 00 — J y ® I
Р/О | AC METERING CIRCUIT A - A TR 2 RS OY Re
A? CUIT ASSEMBLY (00427-66502) 7} | ® , 5% 8870 I
| 4 | |
| о® | — _
XE———— 1 6.7V
ASSEMBLY
Jv” MOUNTING I
SCREW |
P/0 À | | I | 20
К Те —6.7V !
| ca |
| Te ! !
' I [RANGE]
f ; AC METERING CIRCUIT = 7 OHMS CAL «===, (Г) SIC(F)
+6. TV №
| XID I ®
|
I I 906, Ру AA 4 Sle, (3) я
В I Ъ CF Rig a
xx 500 (a
400 CPS 2 cw 5 ®
HO MV R20 RI
— 5K 8870
Cw ” I
Ri7
IK |
RIE |
59,0 8
.
I
I
01791-2
Figure 6-3. Schematic Diagram
6-3
HE
Sectio
n VII Model 427A
MPI MP2
MP3
MPIC
MPa
MPO
4274 -B- 05404
MPil
MPI3 MPI4
MP& MPS
: OPTION Ol ONLY
Figure 7-1.
Location of Mechanical Parts
01791-1
M
an
7-2
ref
cat
tog
fol
01791
Р
Pn
Model 427A
Section VII
SECTION VII
REPLACEABLE PARTS
7-1. INTRODUCTION.
7-2. This section contains information for ordering
replacement parts. Table 7-1 lists parts in alpha-
meric order of their reference designators and indi-
cates the description, -hp- part number of each part,
together with any applicable notes, and provides the
following:
a. Total quantity used in the instrument (TQ)
column).
b. Description of the part. (See list of abbrevia-
tions below. )
с. Typical manufacturer of the part in à five-
digit code. (See Appendix A for list of manu-
facturers. )
а, Manufacturer's part number.
7-3. Miscellaneous parts are listed at the end of
Table 7-1. Each factory selected component is keyed
to paragraph describing the selection of the component
value,
7-4. ORDERING INFORMATION.
7-5, To obtain replacement parts, address order or
inquiry to your local Hewlett-Packard Field Office.
(See Appendix B for list of office locations. ) Identify
parts by their Hewlett-Packard part numbers,
7-6. NON-LISTED PARTS.
7-7, To obtain a part that is not listed, include:
a, Instrument model number.
b. Instrument serial number,
с, Description of the part.
d. Function and location of the part.
DESIGNATORS
А = assembly F = fuse MP = mechanical part TC = thermocouple
B = motor FL = filler T = plug Y = vacuum tube, neon
BT = battery HR = heater q = trengistor bulb, photocell, etc.
© = capacitor IC = integrated circuit ен. = transislor-diode Ww = cable
CR = diode — J = jack R = resistor X = socket
DL - delay line E = relay RT = thermistor ADS = lampholder
Ds = lamp L = inductor 5 = switch XF — fuseholder
E = mise electronic part M = meter T = transformer É = network
ABEREYIATIONS
= silver ID = inside diameler ns = nanosecond {a) = 1079 al = slide
Al = aluminum Impe = impregnaled seconds SPDT = single-pole double-
A = alnpere {s) ined = incandescent ns? = not separalely replace- throw
Au = gold 108 = insulation {ud} able SPET = Single-pole single-
с _ throw
cer _ capacitor ES: — kilolhm (a) = 10% chris 0 = ohm (s) Ta - tantalum
A = coefficient kHz — = klchertz = 10** hertz 004 order by description TC = Lemperature coefficient
com = common = outside diameter TiO - titanium dioxide
comp = composition L = inductor р peak 2
«ann = connection lin = linear taper - , - Lor = toggle
dep ~ deposited lug = logarithmic taper pe = printed circuit 1 a = nes
DPDT —= double-polc double - - - pi = 107 rim | = (rimmer
roe? m = mili = 10% pF picofarad (s) = 10 TSTR = transislor
DPST = double-pole single- mA = milliampere (8) = 1073 ply = peak inverse voltage Y = volt (s)
row amperes +8 p/0 = part of vacw = aliernating current
MHz = megahertz = 10 heriz pos = position (3) working vollage
elect = electrolytic Me = megohm-{s) = 10*% ohms poly = polystyrene var - variable
encap —encapsulated met film = metal film pot = potantiomeler часу = direct current working
r = manufacturer Р-р = peak-to-peak voltage
F = farad (e) mig = mounting 3 ppm = parts per million
FFT = field effcet transistor my = millivolt (8) = 107" volte prec = precision (Lamperature Ww = watt (8)
{xd = fixed т, = micro = 10-9 + coefficient, long term w/ = with
GaAs = gallium ars enide uv = microvolt (as) = 10 volts stability, and/or tol- wiv = working inverse voltage
GHz = gigahertz = 10™ hertz my = Mylar erance) w/0 = without
_ -9 ww = wirewound
gd = guard (ed) пА = nancampere (s) = 10 в = resistor ;
Gé = germanium amperes Rh = rhodium * = optimum value selected
grd = ground (ed) NC = normally closed rma = root-mean-square at factory, average
Ne — neon rot = rotary valne shown (part may
H = henry (ies) NO = normally open be omitted)
Hg = Mercury NPO = negative positive zero Se = selenium ++ = no standard type num-
Hz = hertz (cycle (5) per (zero temperature co- seut = section (s) ber assigned (selected
second) efficient) Si = silicon or special type)
REY E ® Dupont de Nemours
01791-2 7-1
Section VII Model 427A
Table 7-1 Replaceable Parts (Cont'd)
REFERENCE -hp-
DESIGNA TOR PART NO. TQ DESCRIPTION MFR. MFR. PART NO.
Al 00427-66501 1 Assembly: board DC Amplifier includes -hp-
C1 thru C6 Q1 thru Q9
CR1 thru СВ5 R1 thru R21
A1C1 0160-0170 1 C: fxd cer 0.22 pF +80% -20% 25 vdcw 56289 | 5C9A obd
A1C2, A1C3 0160-0168 2 C: fxd 0.1 и Е +10% 200 vdew 56289 | 192P10492
A1C4 0150-0093 1 C: fxd 0.01 oF +80% -20% 100 vdew 91418 | TA obd
A1C5 0180-0224 1 C: fxd Al elect 10 pF +75% -10% 15 vdew 56280 | 30D106G015BA4
A1C6 0180-1800 1 С: fxd Al elect 100 uF :100% -10% 6 vdew | 56289 | Non-polar 30D type
obd
A1CRI 1901-0025 1 Diode: Si 100 mA at +1V 100 piv 12 pF -hp-
AlCR2 1902-0568 1 Diode: breakdown 6.2 V +5% 12954 | DZ50801U
A1CR3 thru 1910-0022 5 Diode: Ge HD1872 03877 | obd
A1CR5
A1Q1 1850-0111 2 TSTR: Ge PNP 2N404A 01295 | 2N404A
A1Q2 1854-0087 1 TSTR: Si NPN 2N3417 24446 | 2N3417
AlQ3 1854-0033 2 TSTR: Si NPN 2N3391 24448 | 2N3391
A1Q4 1850-0111 TSTR: Ge PNP 2N404A 01295 | 2N404A
A1Q5 1854-0033 TSTR: Si NPN 2N3391 24446 | 2N3391
A1Q6 1855-0023 1 TSTR: FET SU527 17856 | SU527
A1QT 1854-0057 4 TSTR: Si 2N3855A 24446 | 2N3855A
A1Q8 1853-0036 2 TSTR: Si PNP 2N3306 07263 | obd
A1Q9 1854-0057 TSTR: Si 2N3855A 24446 | 2N3855A
AlR1 0757-0198 1 R: fxd prec met flm 100 ohms +1% 1/2 W 75042 | CEC T-0 obd
А1Н2 0684-5611 1 В: fxd comp 560 ohms +10% 1/4 W 01121 | CB5611
A1R3 0684-1541 1 R: fxd comp 150K +10% 1/4 W 01121 | CB1541
A1R4 0757-0444 1 R: fxd prec met fim 12.1K +1% 1/8 W 75042 | CEA T-O obd
A1R5 2100-1735 1 R: var ww 5 ohms +10% 1-1/2 W 11236 | 110 obd
A1R6, A1R7 0698-4972 2 R: fxd prec met flm 499K +1% 1/2 W 75042 | CEC T-O obd
A1RB 0757-0453 1 В: fxd prec met flm 30. 1K +1% 1/8 W 75042 | CEC T-O obd
A1R9 0757-0454 1 В: fxd prec met flm 33.2K +1% 1/98 W 75042 | CEA T-O abd
А1Н10 0698-4199 1 В: fxd prec met flm 2800 ohms +1% 1/4 W | 19701 | MF6C T-O obd
AlR11 Not assigned
A1R12 0757-0439 1 R: fxd prec met fim 6810 ohms +1% 1/8 W | 75042 | CEA T-O obd
A1R13 0757-0440 2 R: fxd prec met flm 7500 ohms +1% 1/8 W | 75042 | CEA T-O obd
AlR14 0684-3321 1 R: fxd comp 3300 ohms +10% 1/4 W 01121 { CB3321
A1R15 2100-0394 1 R: var ww 300 ohms +20% 1-1/2 W 71450 | 110 obd
A1R16 0698-4205 1 R: fxd prec met flm 21K +1% 1/8 W 75042 | CEA T-O obd
A1R17 0698-4207 1 R: fxd prec met flm 44.2K 21% 1/8 W 75042 | CEA T-O obd
A1R18 2100-0328 2 R: var ww 500 ohms +10% 1-1/2 W 71450 | 110 obd
A1R19* 0757-0408 1 R: fxd prec met flm 250 ohms +1% 1/8 W 75042 | CEA T-O obd
(See Paragraph 5-73)
A1R20 2100-0205 2 R: var ww 5000 ohms +10% 1-1/2 W -hp-
A1R21 0698-4202 1 В: fxd prec met flm 8870 ohms +1% 1/8 W | 75042 | CEA T-O obd
A1R22 0684-3911 1 R: fxd comp 390 ohms +10% 1/4 W 01121 | CB3911
A? 00427-66502 1 | Assembly: board AC Metering Circuit includes | -hp-
C1 thru C9 Q1 thru Q3
CR1 thru CR4 R1 thru R17
A2C1 0180-0039 3 C: fxd elect 100 u F 12 vdew 56280 | 30D107G012DC4M1
A2C2* 0160-0356 1 C: fxd mica 18 pF +5% 300 vdew 04062 | okd
(See Paragraph 5-75)
A2C3 0130-0017 1 C: var cer 8-50 pF 72082 | 557-019-U2PO-34R
A2C4 0180-0060 1 C: fxd elect 200 pF +100% -10% 3 удел 56289 | 30D207G003DC4
A2C5 0180-0033 1 C: fxd elect 50 u F +100% -10% 6 vdew 56289 | 30D506G006CB4M1
A2C6 0180-0039 C: fxd elect 100 uF 12 vdew 56289 | 30D107G012DC4MI1
7-2
01791-3
о =
> =
= >
-
mr reall, 5 a
Model 427A Section VII
Table 7-1. Replaceable Parts (Cont'd)
REFERENCE -hp-
A2CT, A2C8 0180-0064 2 C: fxd elect 35 uF +100% -10% 6 vdew 56289 | 30D356G006BB4
A2C9 0180-0039 С: fxd elect 100 uF 12 vdcw 56289 | 30D107G012DC4M1
A2CRI 1902-0571 1 Diode: zener 14 Y 04713 | SZ10939-224
A2CR2 Not assigned
A2CR3, 1910-0022 Diode: Ge HD1872 03877 | obd
A2CR4
A2Q1, A2Q2 1854-0057 TSTR: Si 2N3855A 24446 | 2N3855A
A203 1853-0023 TSTR: Si NPN 2N3703 01295 | obd
A2R1 0757-0283 1 R: fxd prec met flm 2000 ohms +1% 1/8 W | 75042 | CEA T-O obd
A2R2 0698-4202 1 R: fxd prec met flm 8870 ohma +1% 1/8 W | 75042 | CEA T-0 obd
A2R3 2100-0328 R: var ww 500 ohms +10% 1-1/2 W 71450 | 110 obd
A2R4 2100-0291 1 R: var ww 1500 ohms +20% 1-1/2 W 71450 | 110 obd
A2R5 2100-0205 В: var prec ww 5000 ohms +10% 1-1/2 W -hp-
AIRS 0757-0449 1 В: fxd prec met film 20K +1% 1/8 W 75042 | CEA T-O obd
АЭВТ 2100-0094 1 R: var pot comp lin 50K +30% 1/10 W 71450 | UPE 70RE -hp- obd
A2R8 0757-0465 1 В: fxd prec met flm 100K +1% 1/8 W 75042 | CEA T-O obd
A2R9 0698-4207 1 R: fxd prec met fim 44. 2K +1% 1/8 W 75042 | CEA T-O obd
A2R10 0757-0461 1 НВ; fxd prec met flm 68, 1K +1% 1/8 W 75042 | CEA T-0 obd
A2R11 0757-0419 1 R: fxd prec met flm 881 ohms +1% 1/8 W 75042 | CEA T-O obd
A2R12 0684-2731 1 R: fxd comp 27K +10% 1/4 W 01121 | CB2731
A2R13 0757-0437 1 R: fxd prec met flm 4750 ohms +1% 1/8 W | 75042 | CEA T-O obd
A2R14* 0683-9105 1 R: fxd comp 91 ohms +5% 1/4 W 01121 | CB9105
(See Paragraph 5-717)
A2R15 0757-0440 В: fxd prec met film 7500 ohms +1% 1/8 W | 75042 | CEA T-O obd
A2R16* 0698-4386 1 R: fxd prec met flm 59.0 ohms +1% 1/8 W | 75042 { CEA T-0O obd
(See Paragraph 5-80)
A2R17 2100-2069 1 R: var ww 1000 ohms +20% 1-1/2 W 11238 | 110
Bl 1420-0030 1 Battery: 22-1/2 V dry cell 83740 | No. 763 obd
C1, C2 0170-0022 3 С; fxd my 0.1 и Е +20% 600 vdew 84411 | HEW-27 obd
C3 0132-0003 1 C: var trimmer 0.7 to 3 pF 72982 | 535-016-4R
C4 0140-0152 1 C: fxd mica 1000 pF +5% 300 vdcw 04062 | DM16F102J
C5 0170-0022 С: fxd my 0.1 uF +20% 600 vdew O0OLH | HEW-17 obd
J1 See Option 01
J2 See MP16 and MP18
M1 1120-0903 1 Meter: 100 uA -hp-
R1 0684-1031 1 R: fxd comp 10K +10% 1/4 W 01121 | CB1031
R2 0698-4217 1 В: fxd prec carbon flm 6.837 meg 21% 2 W| 91637] DC2 obd
R3 0730-0113 1 R: fxd prec carbon Ilm 2.163 meg +1% 1 W| 91637 | Dc1 obd
R4 0698-4214 1 В: fxd prec met flm 683. TK +0, 5% 1/4 W 75042 | СЕВ Т-О obd
R5 0898-4212 1 В: fxd prec met flm 216. 3K +0. 5% 1/4 W 75042 | CEB T-O obd
R6 0698-4209 1 R: fxd prec met flm 68. 37K +0, 5% 1/4 W 75042 | CEB T-O obd
RT 0698-4206 1 R: fxd prec met flm 21. 83K +0. 5% 1/4 W 75042 | CEBT-0 obd
R8 0698-4203 1 R: fxd prec met flm 10K +0, 5% 1/4 W 75042 | СЕВ Т-О obd
RY 0884-1051 1 В: fxd comp 1 meg +10% 1/4 W 01121 | CB1051
R10 0698-4128 1 В: fxd prec met flm 10 meg +0. 25% 1/2 W | 03888 PME 70 obd
R11 0698-4129 1 В: fxd prec met flm 31.723K 10.1% 1/4 W | 75042 | CEB T-3 obd
R12 0698-4219 1 В: fxd prec carbon flm 11,74 meg 21% 1 W| 91637 | DC1 obd
R13 0698-4189 1 НВ: fxd prec met film 10, 15 ohms +1% 1/4W| 19701 | MF6C T-O obd
R14 0698-4191 1 R: fxd prec met flm 101.5 ohms +1% 1/4W] 19701 | MF5C T-O obd
R15 0698-4198 1 R: fxd prec met film 1174 ohms +1% 1/4 W | 19701 | MF6C T-0 obd
R16 0698-4204 1 R: fxd prec met flm 11, 75K +1% 1/4 W 19701 | MF6C T-O obd
R17 0698-4210 1 R: fxd prec met film 118.8K +1% 1/4 W 19701 | MF6C T-O obd
R18 0698-4215 1 В: Ixd prec met Пт 1.295 meg +1% 1/2W | 75042 | CEC obd
017913
7-3
Section YI Model 427A
Table 7-1. Replaceable Parts (Cont'd)
REFERENCE -hp-
DESIGNATOR PART NO. TQ DESCRIPTION MFR. MFR. PART NO.
R19 0698-4220 1 НВ: fxd prec carbon flm 67.5 meg +1% 3 W | 91637 | DC2 obd
R20 0898-4194 1 НВ: fxd prec met flm 675 ohms +0.5% 1/4W | 75042 | CEB T-0O obd
R21, R22 0698-4201 2 В: fxd prec met flm 6750 ohms +0, 5% 1/4W| 75042 | СЕВ Т-О obd
R23 0698-4208 1 R: fxd prec met flm 67. 6K +0. 5% 1/4 W 75042 | CEBT-0 obd
R24 0698-4213 1 В; {xd prec met fim 682K 10.5% 1/4 W 75042 | CEB T-O obd
R25 0730-0131 1 В: fxd prec carbon film 7.5 meg +1% 1 W 91837 | DC-1 obd
R26 0698-4200 1 R: fxd prec met flm 3419 chms +0, 25% 1/8 W| 75042 | CEA T-O obd
R27 0698-4197 1 R: fxd prec met flm 1081 ohms +0. 25% 1/8 W| 75042 | CEA T-O obd
R28 0698-4193 1 К: fxd prec metflm 341. 9 ohms +0, 25% 1/8W| 75042 | CEA T-0 obd
R29 0698-4192 1 НВ: fxd prec metflm 108. 1 ohms +0, 25% 1/8W| 75042 | CEA T-O obd
R30 0698-4190 1 R: fxd prec metflm 50 ohms +0. 25% 1/8 W | 75042 | CEA T-O obd
R31 0698-4196 1 R: fxd prec met fIm 1070 ohms +1% 1/8 W 75042 | CEA T-O obd
R32 0757-0418 1 В: fxd prec metflm 819 ohms +1% 1/8 W 75042 | CEA T-O obd
R33 0757-0422 1 R: fxd prec metflm 909 ohms +1% 1/8 W 75042 | CEA T-O obd
R34 0698-4195 1 R: fxd prec metfim 1020 ohms +1% 1/8 W 75042 | CEA T-0 obd
R35, R36 0698-4211 2 R: fxd prec metflm 158K +1% 1/8 W 75042 | CEA T-O obd
R37 2100-1990 1 В: var ww 200 chms +20% DC ZERO/fNœ 71450 | Type 118 obd
61 00427-61902 1 Switch: RANGE -hp-
52 00427-61901 1 Switch: FUNCTION -hp-
00427-69501 Conversion Kit (to Option 01) -hp-
OPTION 01
Cl 0180-1802 1 C: fxd Al elect 150 uF +100% -10% 40 vdew| 56289 | obd
CR1 1901-0025 1 Diode: 8i 100 mA at +1 V 100 piv 12 pF -hp-
Ji 1251-2357 1 Connector: ac power cord receptacle 82389 | AC-3 obd
53 3101-1234 1 Switch: alide DPDT 115/230 42190 | 4633 obd
sa 3101-0011 1 Switch: slide DPDT LINE/BATT 42190 | 4603 obd
Tl 9100-1328 1 Transformer: ac power -hp-
Wi 8120-1348 1 Power cord T0903 | KH-T041
MECHANICAL PARTS
SEE FIGURE 7-1
MP1 5060-5918 1 Cover: top (with handle) -hp-
MP2 5060-0702 2 Assembly: frame 6 x 8 sm -hp=
MP3 00427-00204 1 Panel: rear (Option 01 only) =hp-
MP3 00427-00202 1 Panel: rear —hp-
MP4 5000-0702 2 Cover: side 6 x 8 sm -hp-
MP5 5060-0727 2 Assembly: foot third module -hp-
MP6 5040-0700 2 Hinge -hp-
MP7 1490-0031 1 Stand: tilt third module stainless steel rod | 91260 | obd
MP8 5000-0710 1 Cover: bottom 5 x 8 sm -hp-
MP9 00427-00204 1 Panel: from -hp-
MP10 5020-5388 1 Meter trim: third module -hp-
MP11 0370-0311 1 Thumbwheel: DC ZEROQ/ Ow -hp-
MP12 Not assigned
MP13 1750 A-64A 1 Holder: trimmer capacitor (used with C3) -hp-
MPl4 00427-00601 1 Shield: switch -hp=
7-4 01791-3
~~
а A
>
A
E eme
A
ma
Model 427A Section VII
Table 7-1. Replaceable Parts (Cont'd)
REFERENCE -hp-
DESIGNA TOR PART NO. TQ DESCRIPTION MFR. MFR. PART NO.
MP15 00427-05501 1 | Shield: can (Option 01 only) -hp-
MP16 1510-0009 1 | Assembly: binding post black COM w/o -hp-
solder turret brass, P/O J2
MP17 0340-0099 J | Insulator: binding post single grey plastic -hp-
0, 500'' OD x 0, 200'' ID x 0. 090" thick
with anti-rotation boss, P/Q J2
MP18 1510-0008 1 | Assembly: binding post VOLTS red w/o -hp-
solder turret brass, P/O J2
MP19 1510-0037 1 | Assembly: binding post OHMS blue w/o -hp-
golder turret brass, P/O J2
MP20 0370-0077 2 | Knob: skirted bar 5/8" diameter black for -hp-
1/4" diameter shaft
MP21 00427-06401 1 | Holder: battery -hp-
MP22 00427-90004 1 | Manual: operating and service -hp-
01791-2 7-5
7
— a —_—— Aa. 1 AL " — a л — - = Em aw — ll.
2 MANUAL CHANGES
MODEL 427A
VOLTMETER
Manual Serial Prelixed 947-
-hp- Part No. 00427-90004
Instrument Serial Number Make Manual Changes Instrument Serial Number Make Manual Changes
ALL ERRATA
ERRATA
Section VII, Replaceable Parts:
Delete A2R21 and A2R22.
Change -hp- Part No. of MP3 Panel: rear (Option 01 only) from 00427-00204 to 00427-00205.
Supplement A for 00427-90004
26 February 1970
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement