POTOMAC INSTRUMENTS INC. AG-51 User manual

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INSTRUCTION MANUAL
AUDIO GENERATOR
Model AG-51
POTOMAC INSTRUMENTS, INC.
932 PHILADELPHIA AVE.
PI
SILVER SPRING, MD. 20910

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WARNING
This i nstru rnent rnust be used with a 3 prong U
grounded receptacle outlet. Failure to use a
grounded outlet rnay result in improper opera
tion or safety hazard.
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AUDIO
GENERATOR
MODELAG-51
INSTRUCTION MANUAL
POTOMAC INSTRUMENTS INC.
·
932
Philadelphia Avenue
Silver Spring, Maryland
20910
(301)
589
-
2662
Rev
i
ed
1 February
1979

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WARRANTY
FOR EQUIPMENT
AND
ACCESSORIES
Potomac Instruments Inc. warrants each 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,
which
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
which
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
equipmentpreviously sold.
RETURNING
EQUIPMENT
TO
THE
FACTORY
Factory service is available
for
repair and adjustment
of
this
instrument; however, a
des-
cription
of
the
troub
le, plus
the
model and serial number(s)
of
the
unit
should be
for-
warded first, whereupon instructions
for
correcting
the
troub
le
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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TAB LE OF CONTENTS
Paragraph Title
Page
SECTION 1 GENERAL
DESCRIPTION
l.l
Function
1-1
1.2 Electrical Characteristi
cs
1-1
1.3 Specifications
1- 1
SECTION 2
OPERATING INSTRUCTIONS
2.1
lnstallation
2-1
2.2 Controls and Indicators 2
-1
2.3 Connectors 2-4
2.4
Fuse Location 2-4
2.5 Operating Procedures 2-4
2.5.l
Tum - On Procedure 2-4
2.5.2
Output Mode Selection 2-5
2.6
Application Not es 2-5
2.6.l
Distortion Measurements 2-5
2.6.2
Output Circuit and Termination 2-5
2.6.3 StereoTests 2
-6
2. 6.4
Equipment Performance Measurements 2-6
2.6.5 Grounding 2-6
SECTION 3
TH EORY OF OPERATION
3.1 Overall Description
3-1
3.2
Detailed Theory of Operation
3-1
3.2.1 Variable Frequency
Wien Bridge Oscillator
3-1
3.2.2 Fixed Frequency Wien Bridge Oscillators 3-3
3.2.3 Power Amplifier 3-3
3.2.4
Output Monitor 3-3
3.2.5
Output Attenuator Switching 3-3
3.2.6
Output Mode Switching 3-3
3.2.7 Test/Operate Switching 3-4
3.2.8 Regulated Power Supply 3-4
SECTION 4
MAINTENANCE
4.1 General
4-1
4.2 Periodic Maintenance
4-1
4.3 Alignment Procedure/Performance Test
4-1
4.3.1 Power Supply
4-1
4. 3.2
Oscillator Pre-Amplifier, A6
4-1
4.3.3
Control Amplifier Board, A7 4-2
4.3.4
Output Monitor, Buffer Amplifier, AS
4-3
4.3.5 IM/WF Signal Generator,
A4
4-3
4.3.6
AG-5J Overall Performance Test 4-4
4.4
Troubleshooting,General 4-5
4.5 Circuit Module Troubleshooting 4-6
4.5.1 General 4-6
4.5.2
Power Supply Al
4-6
4.5.3 Power Amplifier/Inverter A2, A3 4-6
4.5.4 IM/WF Generator,
A4
4-6
4.5.5 Buffer Monitor,
AS
4-9
4.5.6
Oscillator Preamp, A6 and Control Amp, A7 4-9

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LIST
OF
TABLES
Table Title
Page
4.1 AG-51 Performance Test
4.4
4.2
Voltage Readings,Power
Amp
/Invert
er
A2
and
A3 4.9
4.3 Voltage Readings, IM/
WF
Generator,
A4
4-10
4.4
Voltage Readings,
Output
Mo
nitor
/
Attenuat
or
Buffer,
AS
4-10
4.5
Voltage Readings, Wien Brid
ge
Oscillator
Pr
e Amp, A6 4-10
4.6
Voltage Readings,
Control
Amp, A7
4-11
4.7
Voltage Readings, Po
wer
Supply AJ
4-11
4.8
Parts
Li
st, AG-51 Chassis 4-29
4.9
Parts List, Power Supply PCB Assembly,
Al
4-30
4.10
Parts List, Po
wer
Amp
/
invert
er
PCB Assembly, A2, A3
4-
31
4.11
Part
s List, fM/WF Signal G
enerator
PCB Assembly,
A4
4-32
4.12
Parts List,
Ou
tp
ut M
on
itor
/B
uffer Amp PCB Assembly,
AS
4.33
4.13
Parts List, Oscillator Pre-Amp PCB Assembly, A6
4.34
4.14
Parts List, Control
Amp
PCB Assembly 4-35/4-36
LIST
OF
ILLUSTRATIONS
Figure
Title
Page
2.1 AG-5 l Controls
and
Indicators 2-2
3.1
AG
-51
Block Diagram 3-2
4.1
Troubleshooting Chart,
Outpu
t Leve
l/
Distorti
on
4-7
4.2
Generator
Frequency
Troubleshooting Chart 4-8
4.3
Circuit Module and
Test
Point Location, AG
-S
I 4-12
4.4
Switch
Configurations 4-13
4.5
Component
Location, Power Supply,
Al
4-14
4.6
Schematic Diagram, PowerSupply,
Al
4-15
4.7
Component
Location, Power Amp/Inverter,
A2,
A3 4-16
4.8
Schematic Diagram, Power
Amp/
lnverter, A
2,
A3 4-17
4.9
Component
Lo
cation,
IM/WF Siganl Generator,
A4
4-18
4.10
Schematic Diagram,
IM
/WF Signal G
ener
ator
,
A4
4-19
4.
I I
Component
Location,
Oulput
Monito
r/
Buffer
, AS 4-20
4.12
Schematic Diagram,
Output
Monito
r/
Buffer, A5 4-21
4.13
Component
Location, Oscillator
Pr
e-Amp, A6
4-22
4.14
Schematic Diagram, OscillatorPre-amp, A6 4-
23
4.15
Component Locati
on,
Control
Amp
, A7 4-24
4
.1
6
Schematic Diagram,
Control
Amp, A7
4-25
/
4-26
4.17
Wiring Diagram, AG-51 4-27/4-28
11

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1.1 FUNCTION
SECTION 1
GENERAL DESCRIPTION
Th e Model AG-5 l Audio Generator furnishes audio signa ls from +20 dBm to - 79.9 dBm* over
the frequency range of 20 Hz to 200 kHz to a 600-ohm load. At a 150 - ohm load, the audio signal levels
are O dBm to - 99.9 dBm. The maximum output level is monitored and can be verified by a built-in test.
1.2 ELECTRICAL CHARACTERJSTICS
The Model AG-5 I generates l ow distortion sine wave signals from 20 Hz to 200 kHz in four
decade ranges. Frequency of the output signal is indicated by a calibrated dial and a range multiplier.
Calibration accuracy is
better than ±3% . It also generates an intermodulation distortion test signal of
60 Hz and 7 kHz mixed in a 4: l ratio. Additionally, it generates a fixed sine wave frequency of 3.15 kHz
for use in wow and flutter measurement. The output attenuator is calibrated in 10, I and 0.1 decibel
steps. When
the AG-5 l is connected to a 600-ohm resistive load, the maximum power output is +20 dBm*
which
may be verified by the buj\t-in test feature.
Separate left and right channel outputs are provided, with switch-selected in-phase, inverse-
phase, left-only
and right-only output signals to facilitate a variety of stereo broadcast system performance
measurements.
1.3 SPECIFICATIONS
Frequency Rang e:
Outputs:
Output Impedanc e:
Unbalanced:
Fully balanced:
Output Level:
Sine Wave Signals:
IM Signal:
Output Level Accuracy:
20 Hz to 200 kHz in four decade ranges.
LEFT only, RIGHT only, LEFT and RIGHT in phase (L&R), or
LEFT and RIGHT 180° out of phase (L-R); switch selected
IM composite
60 Hz and 7 kHz@ 4: 1 ratio (SMPTE standard)
3. 15 kHz fixed wow & flutter signal (IEEE Standard 193-1971)
150
ohms or 600 ohms; switch selected
150 ohms or 600 ohms; switch selected
(No
Attenuation)
+20 dBm* (7. 75V) across 600 ohm load, 15.SV open circuit
0 dBm (.387V) across 150 ohm load, 0.774V open circuit
P
ea k-to - peak voltage of composite waveform is equal to peak-to-
peak voltage of +20 dBm sine wave across 600 ohm load, 0 dB
sine wave across 150
ohm load.
20 Hz - 100 kHz, ±0.2 dB
100 kHz - 200 kHz , ±0.5 dB
*Units
with serial numbers 133 and below have a maximum output le ve l of+ 18 dBm (6.15V RMS) and
and minimum output level of -81.9 dBm.
1-1

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1.3
SPECIFICATIONS
(Cont.)
Attenuator
Range:
Attenuator
Accuracy:
0
to
10
dB:
>
10
dB:
Intrinsi
c
Distortion*
:
Harm
on
ic
50
Hz
to
7.5
kHz
20
ll
z
to
20
kHz
I
ntermodulation
Incide
ntal
FM
(3.15
kHz)
Hum
and
Noise:
Dial
Accuracy:
External
Pow
er:
Dimensions
with
cover,
cm
(in):
Rack
mount
space
with
rack
mount
option
Weight
with
cover, kg Obs):
0
to
99.9
dB
in
0.1 dB
steps
±
1.5%
of
attenuation
in
dB
±0
.2
dB
(max.)
Low
Distortion
<
.05
%
<
.08%
<
.0
3%
<
0.01
%
>
80
dB
below
rated
output
±3%
Fast
Response
< 1%
< 2%
117 VAC,
(230
V
AC
option)
50
or
60
H
z,
9
Watts
38
.
74
(15-1/4)
wide,
13.34
(5-1
/4)
high,
25
.75
(10-1/8)
deep
5¼
inches
5.44
(I
2)
*Slightly
higher
at
R
output
in
L-R,
UNBAL
mode
.
1-
2

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2.1 INSTALLATION
SECTION 2
OPERATING INSTRUCTIONS
The Model AG- 51 is ready for operation as delivered, and need only be connected to an AC
power source.
WARNING
The AG-51 must be used with a 3-prong U-grounded
receptacle outlet. Failure to use a grounded
outlet
may result in improper operation or safety hazard.
2.2 CONTROLS AND INDICATORS
The following controls and indicators are identified on Figure 2-1.
2.2.1 POWER Switch (SI)
Applies AC power to the unit when in the ON position.
2.2.2 POWER Indicator (DSl)
Illuminates to indic ate the presence of main DC (+30V) power.
2.2.3 FREQ Range Switch (S2)
In the XI , XI 0, X100 and XI 000 positions, S2 selects the variable frequency output . The
setting of this switch indicates the multiplier for the calibrat ed FREQ dial (Cl).
In the IM SIG position, S2 selects the special IM distortion test signal (60 Hz+ 7 kHz) output.
The FREQ dial (C 1) has no effect when S2 is in this position.
In the 3.15 kHz position, S2 selects the 3.15 kHz wow and flutter test signal. This signal is
afixed frequency; thus, the FREQ dial wiJI have no effect when this position is selected.
2.2.4 FREQ Dial (Cl)
This calibrated dial may be used to set the desired output frequency with an accuracy of ±3 %,
when the FREQ Range Switch is in the Xl , XIO, XlOO or XlOOO position. The output frequency in
Hertz equals
the dial setting multiplied by the switch setting.
2- 1

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XI
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S6
OS2
S4
FRONT
PANEL
AC
OUT
REAR PANEL
S8
Figure 2.1. AG-51 Controls a
nd
Indicators
2-2
S10
S9
l
OUT
ROUT
+2008M
MAX
• '
J7
JS
GROUND