HP (Hewlett-Packard) 8808A User Manual
TM 11-6625-2872-14&P
TECHNICAL MANUAL
OPERATOR'S, ORGANIZATIONAL,
DIRECT SUPPORT AND GENERAL SUPPORT
MAINTENANCE MANUAL
(INCLUDING REPAIR PARTS AND SPECIAL TOOLS LIST)
FOR
PREAMPLIFIER, LOGARITHMIC
AM-6681(V)1/U
(HEWLETT-PACKARD MODEL 8808A)
(NSN 6625-00-134-3557)
HEADQUARTERS, DEPARTMENT OF THE ARMY
12 MARCH 1981
SAFETY STEPS TO FOLLOW IF SOMEONE IS THE VICTIM OF ELECTRICAL SHOCK
5
12345
DO NOT TRY TO PULL OR GRAB THE INDIVIDUAL
IF POSSIBLE, TURN OFF THE ELECTRICAL POWER
IF YOU CANNOT TURN OFF THE ELECTRICAL POWER, PULL, PUSH, OR LIFT THE
PERSON TO SAFETY USING A DRY WOODEN POLE OR A DRY ROPE OR SOME
OTHER INSULATING MATERIAL
SEND FOR HELP AS SOON AS POSSIBLE
AFTER THE INJURED PERSON IS FREE OF CONTACT WITH THE SOURCE OF
ELECTRICAL SHOCK, MOVE THE PERSON A SHORT DISTANCE AWAY AND
IMMEDIATELY START ARTIFICIAL RESUSCITATION
This manual contains copyright material reproduced by permission of the Hewlett-Packard Company.
TM 11-6625-2872-14&P
TEHNICAL MANUAL HEADQUARTERS
No. 11-6625-2872-14&P WASHINGTON, DC, 12 March 1981
}
OPERATOR'S, ORGANIZATIONAL, DIRECT SUPPORT,
AND GENERAL SUPPORT MAINTENANCE MANUAL
(INCLUDING REPAIR PARTS AND SPECIAL TOOLS LIST)
FOR
PREAMPLIFIER, LOGARITHMIC AM-6681(V)l/U
(HEWLETT-PACKARD MODEL 8808A)
(NSN 6625-00-134-3557)
DEPARTMENT OF THE ARMY
REPORTING ERRORS AND RECOMMENDING IMPROVEMENTS
You can help Improve this manual. If you find any mistakes or if you know of a way to
improve the procedures, please let us know. Mail your letter, DA Form 2028
(Recommended Changes to Publications and Blank Forms), or DA Form 2028-2 located in
back of this manual direct to Commander, US Army Communications and Electronics
Materiel Readiness Command, ATTN: DRSEL-ME-MQ, Fort Monmouth, NJ 07703. In either
case, a reply will be furnished direct to you.
This manual is an authentication of the manufacturer's commercial literature which, through usage, has been
found to cover the data required to operate and maintain this equipment. Since the manual was not prepared in
accordance with military specifications, the format has not been structured to consider levels of maintenance.
i
SECTION 0. INTRODUCTION
Scope...................................................................................................... 0-1 0-1
Indexes of Publications . . . . .. ............................................................. 0-2 0-1
Maintenance Forms, Records, and
Reports ............................................................................................. 0-3 0-1
Reporting Equipment Improvement
Recommendations (EIR).......................................................................... 0-4 0-1
Administrative Storage ............................................................................ 0-5 0-1
Destruction of Army Electronics
Materiel............................................................................................. 0-6 0-1
I. GENERAL INFORMATION
Description .............................................................................................. 1-1 1
II. INSTALLATION
Portable Case or Rack Mounting ............................................................. 2-1 3
Installation in Sanborn Recording
Systems............................................................................................ 2-5 3
III. OPERATION
Operating Controls................................................................................... 3-1 3
Balancing ................................................................................................ 3-9 4
Calibration............................................................................................... 3-11 4
Alternate Calibration Procedure............................................................... 3-12 4
Operation ................................................................................................ 3-14 4
50 dB Span Operation ............................................................................. 3-17 5
100 dB Span Operation ........................................................................... 3-21 5
Operation with Monitoring Instruments ..................................................... 3-25 5
Simultaneous Recording and Monitoring
of 8808A Output................................................................................ 3-27 5
TM 11-6625-2872-14&P
TABLE OF CONTENTS
Paragraph Page
IV. PRINCIPLES OF OPERATION
Output ..................................................................................................... 4-1 6
Stage Description .................................................................................... 4-2 6
Signal Flow.............................................................................................. 4-3 6
Dynamic Range....................................................................................... 4-4 6
Block Diagram Information ...................................................................... 4-5 6
Detector Outputs ..................................................................................... 4-6 6
DB SPAN Switch Circuit.......................................................................... 4-7 6
LOG ZERO Level Setting........................................................................ 4-8 6
V. REPLACEABLE PARTS
Introduction.............................................................................................. 5-1 8
Ordering Information................................................................................ 5-3 8
ii
TM 11-6625-2872-14&P
TABLE OF CONTENTS - Continued
Page
APPENDIX A. REFERENCES.................................................................................................... A-1
B. COMPONENTS OF END ITEM LIST (COEIL)
(Not applicable)
C. BASIC ISSUE ITEMS LIST (BIIL)
(Not applicable)
D. MAINTENANCE ALLOCATION
Section I. Introduction.......................................................................................................... D-1
II. Maintenance Allocation Chart for Plug-In
Amplifier AM-6681(V)1/U .............................................................................. D-3
III. Tool and Test Equipment Requirements for
Plug-In Amplifier AM-6681(V)1/U .................................................................. D-4
iii
TM 11-6625-2872-14&P
LIST OF ILLUSTRATIONS
Number Page
1-1 8808A Log Level Preamplifier.................................................................................................... 1
4-1 8808A Successive Detector ...................................................................................................... 7
4-2 8808A Block Diagram ................................................................................................................ 7
FO 5-1 Model 8808A Log Level Schematic............................................................................................ In back
of manual
LIST OF TABLES
Number Page
1-1 Specifications ............................................................................................................................ 2
3-1 Bottom and Full Scale Signal Levels.......................................................................................... 3
5-1 Reference Designation Index ..................................................................................................... 9
5-2 Part Number - National Stock Number
Cross Reference Index ........................................................................................................ 17
iv
TM 11-6625-2872-14&P
SECTION 0
INTRODUCTION
0-1. SCOPE.
This manual describes Logarithmic Preamplifier AM-6681(V)1/U and provides instructions for operation and
maintenance. Throughout this manual, the preamplifier is referred to as Hewlett-Packard Model 8808A Log-Audio
Preamplifier.
0-2. INDEXES OF PUBLICATIONS.
a. DA Pam 310-4. Refer to the latest issue of DA Pam 310-4 to determine whether there are new editions,
changes, or additional publications pertaining to the equipment.
b. DA Pam 310-7. Refer to DA Pam 310-7 to determine whether there are modification work orders (MWO's)
pertaining to the equipment.
0-3. MAINTENANCE FORMS, RECORDS, AND REPORTS.
a. Reports of Maintenance and Unsatisfactory Equipment. Department of the Army forms and procedures used for
equipment maintenance will be those prescribed by TM 38-750, The Army Maintenance Management System.
b. Report of Item and Packaging Discrepancies. Fill out and forward SF 364 (Report of Discrepancy (ROD)) as
prescribed in AR 735-11-2/DLAR 4140.55/NAVMATINST 4355.73/AFR 400-54/MCO 4430.3E.
c. Discrepancy in Shipment Report (DISREP) (SF 361). Fill out and forward Discrepancy in Shipment Report
(DISREP) (SF 361) as prescribed in AR 55-38/NAVSUPINST 4610.33B/AFR 75-18/MCO P4610.19C and DLAR 4500.15.
0-4. REPORTING EQUIPMENT IMPROVEMENT RECOMMENDATIONS (EIR).
If your equipment needs improvement, let us know. Send us an EIR. You, the user, are the only one who can tell
us what you don't like about your equipment. Let us know why you don't like the design. Tell us why a procedure is hard
to perform. Put it on an SF 368 (Quality Deficiency Report). Mail it to Commander, US Army Communications and
Electronics Materiel Readiness Command, ATTN: DRSEL-ME-MQ, Fort Monmouth, New Jersey 07703. We'll send you
a reply.
0-5. ADMINISTRATIVE STORAGE.
Administrative storage of equipment issued to and used by Army activities shall be in accordance with TM 740-90-1.
0-6. DESTRUCTION OF ARMY ELECTRONICS MATERIEL.
Destruction of Army electronics materiel to prevent enemy use shall be in accordance with TM 750-244-2.
0-1/(0-2 Blank)
SECTION I
GENERAL INFORMATION
1-1. DESCRIPTION.
1-2 The 8808A is a Log Level Preamplifier which
produces a dc output proportional to the logarithm of
the ac input signal, over an extremely wide range of
signal amplitudes. The input signal dynamic range
can be up to 100 dB (100,000:1). In addition, a
50 dB (320:1) span is provided for greater signal resolution
1-3. The Preamplifier is designed for use with low
output impedance accelerometers, as well as vibration
and acoustic transducers, which have outputs in the
frequency range of 5 Hz to 100 kHz. It is also useful
for continuous monitoring or recording of signal output
in dB during frequency analysis of amplifiers, filters,
transmission networks, and similar devices.
1-4. The 8808A can be plugged into Sanborn direct
writing recording systems. When used with recorders
having 50 division chart paper, the calibrated output is
2 dB per division for the 100 dB span, or 1 dB per
division for the 50 dB span. Also, the preamplifier
can be benchtop or rack mounted, with the output
connected to a monitoring instrument such as a
voltmeter or oscilloscope. For recording, a strip
chart recorder or magnetic tape recorder can be
connected to the output.
TM-11-6625-2872-14&P
1-5. The range switch provides nine bottom scale
sensitivities in 10 dB steps from 0 dBV to -80 dBV
(dBV = decibels referred to 1 volt RMS). For the
50 dB span, the full scale signal is 50 dB above the
bottom scale level. For the 100 dB span, the full scale
signal is 100 dB above the bottom scale level.
1-6. All nine RANGE switch positions can be used with
the 50 dB span. The four switch positions outlined in
red on the panel (-50, -60, -70, -80) are used for the 100
dB span only.
1-7. Specifications for the 8808A Log Level Preamplifier are
given in Table 1-1.
Figure 1-1. 8808A Log Level Preamplifier
-1-
TM 11-6625-2872-14&P
Table 1-1. Specifications
ELECTRICAL SPECIFICATIONS
INPUT RESISTANCE: Single-ended to ground 1 megohm minimum.
SIGNAL DETECTION: Full-wave average. 50 dB or 100 dB span, switch selected from front panel.
DETECTION ACCURACY: ± 1 dB maximum error, sine wave input.
MAXIMUM SENSITIVITY: 100 µV rms of sine wave corresponds to bottom scale on most sensitive range.
GAIN STABILITY: Temperature: Less than 2 dB/10°C, 0° to 40°C. Line Voltage: Less than 0.5 dB, 103 to 127 volts.
ATTENUATION: 50 dB span ranges: 9 bottom scale ranges at -80 dBV to 0 dBV in 10 dB steps corresponding to
100 µV, 320 µV, 1 mV, 3.2 mV, 10 mV, 32 mV, 100 mV, 320 mV and 1 volt. Top scale is nominally 50 dB (320X) above
bottom scale.
100 dB span ranges: 4 bottom scale ranges at -80 dBV to -50 dBV in 10 dB steps corresponding to 100 µV, 320 µV, 1 mV
and 3.2 mV. Top scale is normally 100 dB (100,000X) above bottom scale.
ATTENUATION ACCURACY: ± 3% maximum error (0.25 dB) for -80 to -50 dBV attenuation ranges. For other ranges,
detection error (± 1 dB) may add to attenuation error.
OUTPUT: Single-ended to ground, ± 2..5 V maximum or 0 to +5 volts across 1000 ohms minimum.
OUTPUT RESISTANCE: Approximately 10 ohms.
SIGNAL BANDWIDTH: 5 Hz to 100 kHz, less than 3 dB down from mid-band level on SLOW response range. 500 Hz to
100 kHz on FAST response range.
SIGNAL CREST FACTOR: 3 to 1 at full scale on 100 dB span, ±500 volts peak maximum allowed.
DETECTION RESPONSE TIME: For a step change in input amplitude with ratio of 40 dB (100:1) or greater, the time
required for the output to increase or decrease between values corresponding to 105 and 90% of the maximum applied
signal (i.e. , 20 dB below max. applied signal and 1 dB below max applied signal) is approximately 20 msec in FAST
position and 2 sec in SLOW position. i. e. , average rate of change of output under these conditions corresponds to
approximately 900 dB/ sec in FAST: 9 dB/sec in SLOW.
OUTPUT NOISE: Maximum noise appears at bottom scale. 50 dB span: 80 mV pp: 100 dB span: 40 mV pp.
INTERNAL CALIBRATION: -80 and +20 dBV, internally adjustable; -30 dBV accurate to + 0.5 dB. Stability: less than
0.25 dB, 10° to 40°C or 103 to 127 volts; approximately 500 Hz.
GENERAL SPECIFICATIONS
Terminals: DC output on front panel. Input and auxiliary DC output on rear of mating power supply.
Front Panel Controls: RANGE switch; GAIN potentiometer locking; LOG ZERO, 10-turn potentiometer, locking; 50/100
dB SPAN switch; SPAN BALANCE, screwdriver adjust; RESPONSE TIME/CAL switch.
Internal Controls: Signal Board: Balance adjust; CAL adjust (2); Zero Suppression adjust; Attenuator compensation
trimmers (4). Detector Board: 100 dB span mid-scale adjust.
Weight: Approximately 5 lb. (2, 3 kg).
Front Panel Dimensions: 7" high, 2-1/16" wide (178 x 52 mm).
Note: When Preamplifier is used in a recording system, these specifications are affected by performance of the recorder
and driver amplifiers. (Consult data sheet of appropriate system for details.)
All Sanborn 8800 Series Amplifiers are tested for performance under normal production environmental conditions:
ambient temperature 20° to 30° C and relative humidity less than 80% unless otherwise noted.
-2-
TM 11-625-2872-14&P
SECTION II INSTALLATION
2-1. PORTABLE CASE OR RACK MOUNTING.
2-2. The 8808A is operated as a self-contained instrument using an 860-500 Power Supply to furnish operating power for
the preamplifier. The preamplifier power supply combination operates on a 115/230 volt 50 or 60 Hz power line. See the
power supply Operating and Service Manual, IM-860-500-3.
2-3. The preamplifier power supply combination can be mounted in the 860-1400 Case for single channel benchtop
operation. For two channel operation, two preamplifiers and power supplies mount in an 860-200 Module, for benchtop
or rack mounting.
2-4. When the 8808A is operated with the 860-500 Power Supply, preamplifier input and output signal connections are
made on the rear panel of the power supply as follows:
Signal Input Jack J3: Plus (+) signal pin A
Signal ground pin B
Mating connector is 10G3-34FW
Signal Output Jack J2: Plus (+) signal pin A
Signal ground pin E
Mating connector is 10B9-5MW
For monitoring, connect the preamplifier output signal to a voltmeter, oscilloscope, or other voltage indicating instrument
which has a signal range of 0 to +5 volts or 2.5 volts. The output signal can be recorded using a strip chart recorder,
magnetic tape recorder, or other instrument which will operate with an input of 0 to +5 volts, or ± 2. 5 volts.
2-5. INSTALLATION IN SANBORN RECORDING SYSTEMS.
2-6. The 8808A can be installed in Sanborn Recording Systems 7701A, 7702A, 7704A, 7706A, 7708A, for 1, 2, 4, 6, or 8
channels of recording using the heated stylus recording technique. Operating power for the preamplifier is supplied by
the recording system. See the recording system instruction manual for installation information.
2-7. The 7701A Recorder is supplied in a portable case. The 7702A Recorder is supplied either in a mobile cart, or for
rack mounting. The 7706A, 7708A Recorders are rack mounted.
SECTION III OPERATION
3-1. OPERATING CONTROLS.
3-2. RANGE switch selects the bottom scale
signal level. Scale is calibrated in dBV
(decibels referred to a 1 volt rrns signal). Full
scale signal for 50 Db span operation is 50 dB
50 DB SPAN
Range
Switch Bottom Scale Full Scale
Setting dBV Volts rms dBV Volts rms
above bottom scale signal. For 100 dB span,
full scale signal is 100 dB above bottom scale
signal. Bottom scale and corresponding full
scale signal levels for each setting of the
RANGE switch are given in Table 3-1.
3-3. DB SPAN switch selects either 50 dB or
100 dB maximum span between the bottom
scale and full scale input signal levels.
NOTE
On the 100 dB span, only the 50, -60, -70, -80 RANGE switch
positions are used.
Switch also indicates recorder calibration: 1
dB/div for 50 dB span. 2 dB/div for 100 dB
0 0 1 V +50 316 V
-10 -10 .316V +40 100 V
-20 -20 .100V +30 31.6 V
-30 -30 31.6 mnV +20 10 V
-40 -40 10 mV +10 3.16 V
-50 -50 3.16 mV 0 1 V
-60 -60 1 mV -10 .316 V
-70 -70 316 µV -20 .1 V
-80 -80 100 µV -30 31.6 mV
100 DB SPAN
-50 -50 3.16 mV +50 316 V
-60 -60 1 mV +40 100 V
-70 -70 316 µV +30 31.6 V
-80 -80 100 µV +20 10 V
span.
Table 3-1. Bottom and Full Scale Signal Levels
-3-
TM 11-6625-2872-14&P
3-4. GAIN control sets the preamplifier output level for a full scale cal signal applied to the preamplifier input. For use in
recording systems, full scale output corresponds to the top division on the recorder chart ( approx. -2.5 volts preamp
output). For use with a voltmeter or oscilloscope, full scale output is +5 volts.
3-5. LOG ZERO control sets the preamplifier output level for a bottom scale cal signal applied to the preamplifier input.
For use in recording systems, bottom scale output-corresponds to the bottom division on the recording chart (approx. -2.5
volts preamp output). For use with a voltmeter or oscilloscope, bottom scale output is 0 volts.
3-6. SPAN BALANCE control balances the preamplifier, to obtain the same output on the 100 and 50 dB spans for a -80
dBV calibration signal level.
3-7. RESP TIME,/CAL DB switch selects the operating mode. FAST and SLOW response times are the use positions.
OFF position disconnects the input signal from the preamplifier, and grounds the preamplifier input. -80, -30, +20 dB
CAL positions select calibration voltage levels supplied by a 500 Hz oscillator in the preamp.
3-8. OUTPUT jack provides the preamplifier output signal at the front panel, for monitoring purposes. Mates with 10G222MW plug.
3-9. BALANCING
3-10. Allow preamplifier to warm up several minutes before balancing.
a. Set the RESP TIME/CAL DB and RANGE switches to the -80 position.
b. Adjust the LOG ZERO control for approximately bottom scale output.
c. Alternately set the DB SPAN switch to the 50 and 100 positions while adjusting the SPAN BALANCE control for
minimum change in the preamp output.
NOTE
Approximately ± 20 mnV noise normally present at the preamplifier output will cause a slight
fluctuation in the reading observed on a voltmeter or oscilloscope connected to the output.
3-11. CALIBRATION
a. Set the DB SPAN switch to 100.
b. Set the RANGE switch to 80.
c. Set the RESP TIME/CAL DB switch to -80.
d. Adjust the LOG ZERO control for bottom scale output.
e. Set the RESP TIME/CAL DB switch to +20 and adjust the GAIN control for full scale output.
f. Repeat steps 3-11 (c) through 3-11 (e) to eliminate the effects of control interaction.
g. Set the RESP TIME/CAL DB switch to OFF. With the switch OFF, a negative voltage is normally present at the
preamp output, which will position the recorder stylus offscale.
NOTE
Preamp RANGE switch must be in the -80 position during the calibration procedure.
3-12. ALTERNATE CALIBRATION PROCEDURE.
3-13. To calibrate the preamplifier with the DB SPAN switch in the 50 dB position, use the below procedure:
a. Set the DB SPAN switch to 50.
b. Set the RANGE switch to -80.
c. Set the RESP TIME/CAL DB switch to -80.
d. Adjust the LOG ZERO control for bottom scale output.
e. Set the RESP TIME/CAL DB switch to -30 and adjust the GAIN control for full scale output.
f. Repeat steps 3-13 (c, d, e) to eliminate the effects of control interaction.
g. Set the RESP TIME/CAL DB switch to OFF. With the switch OFF, a negative voltage is normally present at the
preamp output, which will position the recorder stylus offscale.
3-14. OPERATION
3-15. Set RESP TIME/CAL DB switch to OFF. Connect input signal to preamplifier. For applications where preamplifier
is installed in Sanborn recorder, the output signal is displayed on recorder chart paper. For applications where the
preamplifier output is to be monitored with an oscilloscope or voltmeter, the output is available from the preamplifier front
panel OUTPUT jack, or from a rear connector on the preamplifier power supply.
3-16. Set the DB SPAN switch to the 50 dB or 100 dB position, depending on the expected range of input signal
amplitudes.
-4-
TM 11-6625-2872-14&P
3-17. 50 dB SPAN OPERATION.
3-18. Set the RANGE switch to the position which corresponds to the minimum expected signal level. See examples 1
and 2.
EXAMPLE 1: Minimum expected signal level 10 mnV rms. This corresponds to a -40 dBV signal level (see Table 3-1).
Set the RANGE switch to the -40 dBV position. The full scale signal level is 50 dB higher:
-40 dBV
add +50 dB
+10 dBV = Full scale input signal = 3.16 volts rms
EXAMPLE 2: Minimum expected signal level .5 volt rms. This corresponds to a -6 dBV signal level. Since there is no 6 dBV switch position, set the switch to the next lower step, which is -10 dBV. The full scale signal level is 50 dB higher:
-10 dBV
add +50 dB
-40 dBV Full scale input signal = 100 volts rms
3-19. Set the RESP TIME/CAL DB switch to the FAST or SLOW position, depending on the signal bandwidth, and the
detection response) time desired. (For FAST response, the preamp) bandwidth is 500 to 100,000 Hz. For SLOW
response, bandwidth is 5 to 100,000 Hz.)
3-20. For 50 division chart paper, the calibration is 1 dB/div. The bottom division on the chart represents the bottom
scale signal level in dB indicated on the RANGE switch.
3-21. 100 dB SPAN OPERATION.
3-22. Only the four RANGE switch positions outlined in red (-80, -70, -60, -50) are used for the 100 dB span. Set the
RANGE switch to the position which corresponds to the expected minimum signal level.
EXAMPLE 1: Minimum expected signal is 1 mV rms. This corresponds to a -60 dBV level (see Table 3-1). Set RANGE
switch to the - 6OdBV bottom scale position. The full scale signal level is l00dB higher:
- 60 dBV
add +100 dB
+ 40 dBV = Full scale input signal = 100 volts rms
EXAMPLE 2: Minimum expected signal is
500 µV rms. This corresponds to a -66 dBV level. Set the RANGE switch to the next lower step, which is the -70 dBV
bottom scale position. The full scale signal level is 100 dB higher:
- 70 dBV
add +100 dB
+ 30 dBV = Full scale input signal = 31.6 volts rms
3-23. Set the RESP TIME/CAL DB switch to the FAST or SLOW position, depending on the signal blind bandwidth, and
the detection response time desired. (For FAST response, the preamp bandwidth is 500 to 100,000 Hz. For SLOW
response, bandwidth is 5 to 100,000 Hz.)
3-24. For 50 division chart paper, the calibration is 2 dB/div. The bottom division on the chart represents the bottom
scale signal level in dBV indicated on the RANGE switch.
3-25. OPERATION WITH MONITORING INSTRUMENTS.
3-26. When the preamplifier output is connected only to a monitoring instrument such as a dc voltmeter or oscilloscope,
perform the balancing (Section 3-9) and calibration (Section 3-11) procedure as indicated. Bottom scale output refers to
0 volts preamplifier output. Full scale output is -5 volts preamplifier output. The 50 dB span calibration is .1 volts/dB.
The 100 dB span calibration is .05 volts/dB.
3-27. SIMULTANEOUS RECORDING AND MONITORING OF 8808A OUTPUT.
3-28. To simultaneously record and monitor the 8808A output signal, perform the balancing and calibration procedure
using the recorder. The dc voltmeter, oscilloscope, or other monitoring instrument connected to the output of the preamp
will read approximately -2.5 volts for a bottom scale input signal, and approximately +2.5 volts for a full scale input
signal. The monitor instrument calibration is .1 V/dB on the 50 dB span, and .05 V/dB on the 100 dB span.
-5-
Loading...