POTOMAC INSTRUMENTS INC. AA-51 User manual

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INSTRUCTION MANUAL
AUDIO ANALYZER
Model AA-51
POTOMAC INSTRUMENTS, INC.
932 PHILADELPHIA AVE.
PI
SILVER SPRING, MO. 20910

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WARNING
This instrument must be used with a 3 prong U-
grounded receptacle outlet. Failure to use a
grounded out l et may result in improper opera-
tion or safety hazard.
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AUDIO ANALYZER
MODEL AA-51
INSTRUCTION MANUAL
POTOMAC INSTRUMENTS INC.
932
Philadelphia Av
enue
Silver Spring, Maryland
20910
(301)
589-2662
Revised 1 February 1979

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l
\
WARRANTY FOR EQUIPMENT AND ACCESSORIES
Potomac Instruments Inc. Warrantseach new equipment to be free of defects in material
and workmanship,
for a period of one (1) year after date of original shipment, except for
fuses, transistors, diodes, and integrated circuits, wh ich are warranted for a period of
ninety (90) days. Any instrument which is found within one year not to meet the fore-
going standards
after examination by our factory, will be repaired or at the option of
Potomac Instruments replaced without charge. This warranty does not apply to equip-
ment wh ich has been altered, improperly handled, or damaged in any way.
CHANGES IN SPECIFICATIONS
The right is reserved to change the published specifications of equipment at any time, and
to furnish merchandise in accordance with current specifications, without incurring any
liability to modify equipment previously sold.
RETURNING EQUIPMENT TO THE FACTORY
Factory service is available for repair and adjustment of this instrument; however, a des-
criptio n of the trouble, plus the model and serial number(s) of the unit should be for-
warded first, whereupon instructions for correcting the trouble or authorization for
returning the equipment will be given. This applies to all units, whether under warranty
or not. Shipment in an improper container may result in damaged equipment thereby
voiding warranty.

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TABLE OF C ONT ENT S
Paragraph
Title
Page
SECTION 1 GENERAL DESCRIPTION
1.1
Function
1-1
1.2 Specifications, AA-51 1
-1
SECTION 2
OPERATING INSTRUCTION S
2.1 Installation
2-1
2.2 Controls and Indicators
2-1
2.3 Connectors 2-3
2.4
Fuse Location 2-4
2.5
Adjustment of Mechanical Zero 2-4
2.6 General Operating Information 2-4
2.7 Operating Procedures 2-5
SECTION 3
THEORY OF OPERATION
3 .1
General Description 3-1
3.2
Block Diagram Description 3-1
3.3 Detailed
Theory of Operation 3-3
3.3.1 Signal Leveler (BD41), A2 3-3
3.3.2 Phase
and Ratio Detector (BD 40 ), A3
3-4
3.3.3 IM/WF Demodulator (BD42),
AS
3-5
3
.3.4
Null Amp (A6) and Quadrature Detector (A4)
3-6
3.3.5 Voltmeter Circuits (BD43, BDS0,
BDS l)
3-8
3.3.6 Regulated Power Supply,
Al
3 -9
SECTION 4 . MAINTENANCE
4. I General 4-1
4.2 Periodic Maintenance
4-1
4.3 Alignment Procedure/Performance Test 4-1
4.4 Troubleshooting, General 4-6
4.5 C
ir cuit Module Troubleshooting 4-7
4.5.1 General 4-7
4.5.2 Power Supply,
Al
4-7
4.5.3 Leveler, A2 4-7
4.5.4
Phase and Ratio Detector, A3 4-7
4.5.5 Quadrature Detector, A4,
and Null Amp, A6 4-8
4.5.6 IM/WF Demodulator,
AS
4-9
4.5.7
Voltmeter Circuit Assembly, A7 4-9

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Table
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
4.
15
4.16
4.17
Figure
2.1
3.1
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
4.15
4.16
4.17
4.18
4.19
LIST
OF
TABLES
Title
AA-5
1
Board-level Troubleshooting
Voltage Readings, Leveler,
A2
Voltage Readings, Phase
and
Ratio Detector,
A3
Voltage Readings, Quadrature Detector, A4
Voltage Readings,
IM/WF
Demodulator,
AS
Voltage Readings, Null Amp, A6
Voltage Readings, Voltmeter, A
7
Part
s List AA-51 Chassis
Parts List, Power Supply
PCB
Assembly,
Al
Parts List, Leveler PCB Assembly, A2
Parts List. Phase and Ratio Detector PCB
Assembly, A3
Parts List, Quadrature Detector
PCB
Assembly,
A4
Parts List,
IM/WF
Demodulator PCB Assembly,
AS
Parts List, Null Amplifier PCB Assembly, A6
Parts List, Noise Filter PCB Assembly,
A
7A1
Parts List, Voltmeter Amplifier, A7A2
Part
s List, Voltmeter Buffer Assembly, A7A3
UST
OF
ILLUSTRATIONS
Title
AA-51 Controls and Indicators
AA-51 Block Diagram
IMD
Test
Signal Network
Circuit Module and Test
Point
Location, AA-5I
Component Location, Power Supply
Al
Schematic Diagram, Power Supply
Al
Component Location, Signal Leveler A2
Schematic Diagram, Signal Leveler A2
Component
Location, Phase and Ratio De
tector
A3
SchematicDiagram, Phase and Ratio Detector A3
Component
Location, Quadrature
Detector
A4
Schematic Diagram, Quadrature
Detector
A4
Component Location,
IM
/WF
Demodulator
AS
Schematic
Di
agram, IM/WF Demodulator
AS
Component Location,
Nu
ll Amp A6
Schematic Diagram, Null
Amp
A6
Component
Locabon, Noise Filter A7A1
Component
Location,
Voltmeter
Amplifier A7A2
Component
Location,
Voltmeter
BufferA7A3
Sch
ema
tic
Diagram,
Voltmeter
Assembly A7
Wiring Diagram,
AA-5
l
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Page
4-6
4-10
4-11
4-12
4-13
4-14
4-15
4-37
4-39
4-40
4-43
4-45
4-47
4-50
4-53
4-54
4-56
Page
2-2
3-2
4-3
4-16
4-18
4-19
4-20
4-21
4-22
4-23
4-24
4-25
4-26
4-27
4-28
4-29
4-30
4-3 l
4-32
4-33/4-34
4-35/4-36

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1.1 FUNCTION
SECTION 1
GENERAL DESCRIPTION
1.1.l Th e Potomac Instruments Model AA-51 Audio Analyzer is a solid state instrument for
measuring ac voltages,
total harmonic distortion (THO), int ermodulation distortion (IMO), signal
plus noise
to noise, relative phase, amplitude ratio, and weighted peak flutter (W&F).
1.1.2 The voltmeter contained in th e Model AA-51 can be used separately for general purpose
voltage
and gain measurements. The voltmeter has a frequency range of 5 Hz to 200 kHz and a
voltage range
of 1 mV to 100 Vrms full scale.
1.1.3 Total hannonic distortion levels of 0.1% to I00% full scale are measured in seven ranges
for any fundamental frequency from
20 Hz to 20 kHz: harmonics are indicated to 100 kHz. InpuI
signals between 0.1 Vrms and 80 Vrms are automatically leveled and no manual adjustment is
required.
Too high or too low input signal levels are indicated by front panel LED 's . A scope output
is provided for use with an oscilloscope. The instrument is capable of an isolation voltage of :!:200 V
above chassis ground.
1.1.4 Intermodulation distortionlevels of 0.1% to 100% full scale are measured in seven ranges
for an SMPTE standard signal
of60 Hz and 7 kHz (4:1 ratio). Input signals between 0.1 Vnns and
80 Vrms are auto matically leveled. Too high or too low input signal levels are indicated by LED's.
1.1.S Noise levels as low as -75 dBm (600 ohms) are measured ina passband of20 Hz to 20 kHz.
1.1.6 Relative phasebetween two signals is measured in two ranges of ±54 degrees and ±180
degrees full scale within a frequency range
of 20 Hz to 20 kHz. Input signals between 0.3 Vrms and
6 Vrms are fully limited;however, the amplitude ratio should be within ±6 dB for best accuracy.
1.1. 7 Amplitude ratio of two signals is measured over a ±6 dB range within the frequency range of
20 Hz to 20 kHz. The input signal levels can be between 0.3 Vnns and 6 Vrms.
1.1.8 Weighted peak
flutter is measured in two ranges of 0.3% and 1% full scale. The input signal
must
be 3.15 kHz ±10% within the amplitude range of 0.1 Vrmsand 80 rms. A wide band (0 .2 Hz
to 200 Hz) scope output is provided.
1.2 SPECIFICATIONS, AA-51
AC Voltmeter
Frequ
ency Range:
Voltmeter Range:
Voltmeter Accuracy:
Input Impedance:
Scope
Outpu t:
20 Hz to 200 kHz
1 mV to 100 Vrms (full scale), 10 dB steps
±3%
(full scale)
330K ohms shunted by 150 pf capacitor
100 mV p-p
(full scale)
1-1

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THD Distortion Meter
Fund amenta l Frequency Range:
Bandwidth :
Di s tortion Range:
Accuracy:
Dynamic Rang e:
Input Impedance :
Scope Output:
Internal Distortion & Noise:
IM Distort ion Meter
Input Signal Required:
Distortion Ran ge:
Accuracy:
Dynamic Range:
Input Imp edance:
Scope Output:
Internal Distortion & Noise:
Signal Plus Noise Meter
Frequency Range (- 3 dB):
Voltmeter Range:
Signal Plus Noise - to-Noise Accuracy:
Residu al Hum & Noise :
Input Imp edance:
Scope Output :
20 Hz to 20 kHz in 3 decade rang es
100 kHz
0.1%
to I 00 % full scaJe
±5% (full scale)
0.1 Vrms to 80 Vrms automatically leveled
SOOK ohms shunted by 105 pf capacitor
100 mV p-p (full scale)
,;;;;Q .04 %, 50 Hz - 7.5 kHz; ,;;;;.08%, 20 Hz - 20 kHz
60 Hz & 7 kHz @ 4: 1 ratio (SMPTE standard)
0.1% to 100%
±5 % (full scale)
0.1
Vrms to 80 Vrms automatically leveled
SOOK ohms shunted by I 05 pf capacitor
100 mV p-p (full scale)
<.03%
20 Hz to 20 kHz
I
mV to 100 Vrms (full scale)
±5% (full scale)
< - 80 dBm
330K ohms shunted by 150 pf capacitor
1 00 mV p-p (full scale)
1-2

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Phase Meter
Rang e:
Bandwidth:
Accuracy:
Dynamic Range:
Input Impedance:
Scope
Output:
Resolution:
Ratio Meter
Range:
Bandwidth:
Accuracy:
Dynamic Range:
Input Impedance:
Scope
Output:
Resolution:
W&F Meter
Range:
In
put Frequency:
Accuracy:
Dynamic Range:
Inpu t Impedance:
Internal Distortion & Noise:
Scope
Output:
± 54 degrees and ±180 degrees
20 Hz to 20 kHz
±5% (full scale)
0.3 Vrms
to 6 Vrms
SOOK ohms shunted by 180 pf capacitor
Rectangular wave
at input frequency, 0. 5V p-p, duty
cycle proportional to phase angle
3 degrees
±6 dB
20 Hz to 20 kHz
±5% (full scale)
0.3 Vrms
to 6 Vrms
SOOK ohms shunted by 1 80 pf capacitor
de voltage proportional to ratio
.:;;;; ±0.25 dB
0.3%and 1% weighted peak flutter in two ranges
3.15 kHz ±10%
±5% (full scale)
0.1 Vfms to 80 Vrms
SOOK ohms shunted by 150 pf capacitor
¾.01%
Bandwidth .2
to 200 Hz, sensitivity 500 mV -p-p (1 %full scale)
1-3

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External Power:
Weight:
Dimensions
(Wx
HxD)
CM
(IN):
115V
or
23
0V
, 50
or 60
Hz
, I
OW
12
lb -
with cover
38.74
X
13.34
X
20.32
(15¼
X
5¼
X
8)
1-4