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TM 11-6625-1576-15 

Section IV

Paragraphs 4-36 to 4-45 and Figure 4-6

Figure 4-6. Rejection Amplifier Block Diagram and Typical Frequency Rejection Characteristic

first stage of amplification, A3Q4, is a field effect

transistor which amplifies the difference signal between
the gate and the source.

The field effect transistor

is selected for maximum noise performance with the
high impedances of the Wien bridge circuit. The signal

from the drain is applied to the two stage feedback am-
plifier A3Q5 and A3Q6. The output of A3Q6 is coupled

to the meter circuit by the post attenuator S3R1 through
S3R11. Negative feedback from the output of the bridge
amplifier is applied to the preamplifier circuit to nar-
row the frequency rejection characteristic. It can be
noted from the rejection characteristic (refer to Figure
4-4) for the bridge that the rejection of harmonic volt-
ages is not constant. Typically the second harmonic

is attenuated several db more than the third harmonic
and the third more than the fourth. The result of the
negative feedback is illustrated by the rejection charac-

teristic shown in dashed lines on the attenuation and

phase characteristic of Figure 4-4. Figure 4-6 shows
a simplified block diagram of the rejection amplifier
with the typical frequency-rejection characteristic.

Refer to Figure 4-7, Bandwidth Versus Null Depth for
further detail on the rejection characteristic.

4-36. HIGH PASS FILTER.

4-37. The HIGH PASS FILTER (see Figure 6-3) is
normally used when the fundamental of the input signal
is greater than 1 Kc.

In the voltmeter mode of opera-

tion, the filter is not used. In the SET LEVEL and
DISTORTION position of the FUNCTION switch the
filter presents >50 db attenuation to 50 or 60 cycle

hum components, but offers no attenuation to frequen-
cies over 1 Kc.

The filter assembly, A7, consists of

A7C1, A7C2, and A7L1. The filter can be inserted
or bypassed by the HIGH PASS FILTER switch, S9.

4-38. METER CIRCUIT.

4-39. The meter circuit (refer to Figure 6-4) consists
of the post attenuator, the meter amplifier circuit,
and the meter rectifier circuit.

4-40. POST ATTENUATOR.

4-41. The post attenuator, S3R1 through S3R11, is a
series of resistive networks which attenuate the input
signal in 10 db steps.

The attenuator is used in con-

junction with either the input sensitivity attenuator or

the 1000:1 attenuator to limit the signal level to the
meter amplifier to 1 mv for full scale deflection on
all ranges from 1 mv to 300 v full scale. The meter
circuit sensitivity is increased to 300 uv for full scale
deflection on the 300 u

range by switching resistors

A2R29 and A2R30 into the calibration network. Resis-

tor A2R41 and capacitor A2C29 are also switched into

the calibration network on the 300 

P

v range to extend

the passband of the amplifier.

4-42. METER AMPLIFIER CIRCUIT.

4-43. The meter amplifier circuit consists of a five
stage amplifier circuit, A2Q5 through A2Q9, which
develops the current for full scale meter deflection.
Negative dc feedback from the emitter circuit of
A2Q8 is applied to the base of A2Q5 to stabilize the
dc operating point of the meter amplifier circuit and
to minimize the tendency for dc drift due to ambient
temperature changes. A2R51 and A3CR8 are electric-
ally in the circuit only when the meter circuit is over-

loaded. When the voltage on the emitter of A2Q9 be-
comes abnormally large during an overload, A2CR8
breaks down and provides a lower resistance charging
path for A2C15 which reduces the transient recovery
time of the meter circuit. Negative ac feedback is
applied from the collector circuit of A2Q9 to the emit-
ter circuit of A2Q5. This feedback is used to ensure
flat frequency response, to improve linearity, and to

reduce the effect of variation of transistor parameters

with environmental changes. In this manner, the

calibration of the instrument is made dependent on
high quality passive components.

4-44, METER RECTIFIER CIRCUIT.

4-45. The meter rectifier is connected in a bridge type
of configuration with a diode in each upper branch and
a dc milliammeter connected across the midpoints of
the bridge. The simplified meter rectifier is illu-
strated in Figure 4-8.

The generator represented by

A2Q5 through A2Q9 with the internal impedance R

O

provides the meter, M1, with current for full scale
deflection and develops a voltage across the calibration
network which closes the ac feedback loop. Capacitors
A2C27 and A2C28 are used as coupling capacitors for
the ac feedback loop, output signal to the OUTPUT

connector, and the bridge error signal to the input of
the automatic fine tuning loops. The mechanical inertia
of the meter and A2C26 prevents the meter from re-
sponding to individual current pulses.

Therefore,

the meter indication corresponds to the average value
of the current pulses rather than the peak value. The
meter is calibrated to indicate the rms value of a sine
wave. Resistor A2R45 impresses a fixed bias across
diodes A2CR6 and A2CR7 (biasing them close to the
barrier voltage) to make the meter circuit response

linear to large variations in signal amplitude. The
linearity of this type of circuit is also increased by
including the meter circuit in the overall feedback
loop.

4-5

Summary of Contents for 333A

Page 1: ...1 6625 1576 15 DEPARTMENT OF THE ARMY TECHNICAL MANUAL ORGANIZATIONAL DS GS AND DEPOT MAINTENANCE MANUAL DISTORTION ANALYZER HEWLETT PACKARD MODELS 333A AND 334A HEADQUARTERS DEPARTMENT OF THE ARMY MAY 1967 ...

Page 2: ...TM 11 6625 1576 15 WARNING DANGEROUS VOLTAGES EXIST IN THIS EQUIPMENT Be careful when working on the power supply and on the 115 volt ac line connections DO NOT TAKE CHANCES ...

Page 3: ...stortion Measurement in AM Carriers 4 1 4 8 Voltmeter Operation 4 1 4 10 Schematic Theory 4 1 4 11 Impedance Converter Circuit 4 1 4 14 Rejection Amplifier Circuit 4 2 4 36 High Pass Filter 4 5 4 38 Meter Circuit 4 5 4 46 Power Supply Circuit 4 7 4 51 RF Detector Circuit 334A only l 4 7 Section Page V MAINTENANCE 5 1 5 l Introduction 5 1 5 2 Test Equipment Required 5 1 5 5 Performance Checks 5 1 S...

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Page 5: ...TM 11 6625 1576 15 Model 333A 334A Section 1 Figure 1 1 and Table 1 1 Figure 1 1 Model 333A Distortion Analyzer 1 1 Table 1 1 Specifications ...

Page 6: ...TM 11 6625 1576 15 Section I Model 333A 334A Table 1 1 Table 1 1 Specifications Cont d 1 2 ...

Page 7: ...t h r o u g h p u b l i c a t i o n s s u p p l y c h a n n e l s T h e i n d e x l i s t s t h e i n d i v i d u a l p a r t s 1 0 2 0 3 5 P e t c a n d t h e l a t e s t c h a n g e s t o a n d r e v i s i o n s o f e a c h e q u i p m e n t p u b l i c a t i o n l A 3 F o r m s a n d R e c o r d s a R e p o r t s o f M a i n t e n a n c e a n d U n s a t i s f a c t o r y E q u i p m e n t U s ...

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Page 9: ...s a fre quency range of 5 cps to 3 Mc 20 cps to 500 Kc for 300 pv range and a voltage range of 300 pv to 300 v rms full scale 1 5 The AM detector included in the Model 334A is a broadband dc restoring peak detector consisting of a semiconductor diode and filter circuit AM distortion levels as low as O 3 can be measured on a 3 v to 8 v rms carrier modulated 30 in the standard broadcast band and low...

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Page 11: ...pin on the power cable three prong connec tor is the ground wire 2 9 To preserve the protection feature when operat ing the instrument from a two contact outlet use a three prong to two prong adapter and connect the green pigtail on the adapter to ground 2 10 INSTALLATION 2 11 The Model 333A 334A is fully transistorized therefore no special cooling is required However the instrument should not be ...

Page 12: ...TM 11 6625 1576 15 Section III Model 333A 334A Figure 3 1 Figure 3 1 Front and Rear Panel Description 3 0 ...

Page 13: ...ver age to effective values in a true sine wave is approxi mately O 9 to 1 When the meter is used to measure complex waves the voltage indicated may not be the rms value of the signal applied This deviation of meter indication exists because the ratios of average to effective values are usually not the same in a com plexwave as in a sine wave The amount of deviation depends on magnitude and phase ...

Page 14: ... SET LEVEL position thus making the next range 30 etc h Adjust SENSITIVITY VENIER control for full scale deflection j Position FRIQUENCY RANGE selector and frequency dial to fundamental frequency of input signal 3 2 Model 333A 334A k Position FUNCTION selector to DISTORTION m Adjust METER RANGE selector and frequency dial vernier control for minimum meter indication n Adjust COARSE and FINE BALANC...

Page 15: ...tion III Paragraphs 3 23 to 3 27 3 25 The 333A and 334A perform as general purpose AC Voltmeters when the FUNCTION selector is set to VOLTMETER position NOTE With the FUNCTION selector in VOLT METER position the SENSITIVITY se lector is disabled a Position METER RANGE selector to a range exceeding the value of the signal to be measured b Connect signal to INPUT terminals c Select a METER RANGE to ...

Page 16: ...F i g u r e 4 1 B l o c k D i a g r a m T M 1 1 6 6 2 5 1 5 7 6 1 5 S e c t i o n I V F i g u r e 4 1 Model 333A 334A ...

Page 17: ...ost attenuator is used to limit the input signal level applied to the metering circuit to 1 mv for full scale deflectlon The metering circuit sensitivity is increased to 300 uV for full scale deflection on the 300 pv range The metering circuit provides a visual indication of the OPERATION distortion level of the input signal In addition to the visual indication provided by the meter the OUTPUT ter...

Page 18: ...g the bridge output using the input signal as a reference 4 20 When the Wien bridge is not tuned exactly to the frequency to be nulled a portion of the fundamental frequency will appear at the bridge output The phase of this signal depends on which leg of the bridge is not tuned or on the relative errors in tuning if neither is set correctly The magnitude of the signal is propor tional to the magn...

Page 19: ...of the FREQUENCY RANGE switch S4 switches A5R56 in parallel with A5R55 on the top three frequency ranges A6DS2 will become brighter and lower the resistance of A6V2 through A6V5 making variation in resistance less than on the two lower ranges However less variation in resistance is needed to tune the leg because the impedance in the reactive leg becomes progressively less as the higher frequency r...

Page 20: ...tector A5Q4 4 30 Refer to Figure 4 5 simplified partial schematic for detector operation The discussion is applicable to both resistive and reactive detector circuits 4 31 The signals from the error amplifier A5Q2 and A5Q3 will be equal and of opposite phase and will cancel out each other when the detector A5Q4 is off However when the positive half of the reference square wave gates A5Q4 on the si...

Page 21: ...tivity is increased to 300 uv for full scale deflection on the 300 uV range by switching resistors A2R29 and A2R30 into the calibration network Resis tor A2R41 and capacitor A2C29 are also switched into the calibration network on the 300 Pv range to extend the passband of the amplifier 4 42 METER AMPLIFIER CIRCUIT 4 43 The meter amplifier circuit consists of a five stage amplifier circuit A2Q5 thr...

Page 22: ...TM 11 6625 1576 15 Section IV Figure 4 7 Model 333A 334A Figure 4 7 Bandwidth Versus Null Depth 4 6 ...

Page 23: ...nal series regulator type and operates the same as the 25 volt regulated supply 4 50 Diodes A1CR5 and A1CR6 are coupling and pro tection diodes for external battery supplies The diodes protect the series regulator circuits from application of incorrect polarity at the battery input terminals The diodes also protect external batteries from being charged when the ac power is being used with batterie...

Page 24: ...TM 11 6625 1576 15 Section V Table 5 1 Model 333A 334A Table 5 1 Test Equipment Required 5 0 ...

Page 25: ...as follows MIN Position 1 next step Position 2 etc to Max Position 6 5 9 FUNDAMENTAL REJECTION CHECK a b S e t Connect 33lA 332A as shown in Figure 5 1 Set Distortion Analyzer controls as follows FUNCTION Selector VOLTMETER METER RANGE Selector 1 VOLT FREQUENCY RANGE Selector X1OO Frequency Dial 50 filter White Instr Lab Model 2640 5Kc on Distortion Analyzer meter d Switch Distortion Analyzer FUNC...

Page 26: ...control for a O db indication on the Distortion Analyzer meter h Switch Distortion Analyzer FUNCTION selector to DISTORTION The meter reading shall not change more than 0 6 db Model 333A 334A j Repeat steps a through h at the frequency settings indicated in Table 5 2 The meter readings shall change within the limits specified Table 5 2 Second Harmonic Accuracy Check 5 11 a b c DISTORTION INTRODUCE...

Page 27: ...t Check 5 12 FREQUENCY CALIBRATION ACCURACY CHECK b c TM 11 6625 1576 15 Section V Paragraph 5 12 Table 5 3 and Figure 5 3 NOTE From 5 cps to 10 cps the FREQUENCY dial may be as much as 3 low In this test the dial is held constant and the in put frequency is varied and monitored If the dial is low the input frequency at null will be high If the period of the in put frequency is measured it will be...

Page 28: ...eter shall indicate less than 30 pf d Switch the Distortion Analyzer on the 0 3 range and measure capacitance Meter shall indicate less than 60 pf 5 4 e Set Distortion Analyzer controls as follows FUNCTION Selector DISTORTION SENSITIVITY Selector MIN METER RANGE Selector VOLTS f Measure Capacitance at each SENSITIVITY selector setting of the Distortion Analyzer The L C meter shall indicate less th...

Page 29: ...ut c Set Distortion Analyzer FUNCTION Selector to VOLTMETER d Set voltmeter calibrator for 400 cps output e Check the Distortion Analyzer voltmeter full scale readings on all ranges against the appropriate rms input voltages from the voltmeter calibrator The voltmeter accuracy shall be within 2 f Set the Distortion Analyzer METER RANGE selector to 1 VOLT range Transformer set to 105 v 125 v 5 18 H...

Page 30: ...l indicate 0 9 the toler ances indicated k Switch the Frequency Response Test Set RANGE SELECTOR to the 1 3 Mc position Set the FREQ TUNING dial to the frequencies listed in Table 5 5 Adjust the Frequency Response Test Set AMPLITUDE control until the meter indicates SET LEVEL after each frequency setting The Distortlon Analyzer meter shall indicate 0 9 the tolerances indicated 5 6 n Repeat steps b...

Page 31: ... 33 Adjustment locations are shown in Figure 5 8 5 24 The Adjustment and Calibration Procedure is performed with the ac power cord connected to nomi nal line voltage 115 v 230 v 50 to 1000 cps MODE switch to MANUAL HIGH PASS FILTER to OUT and NORM RF DET switch to NORM unless otherwise specified 5 25 METER MECHANICAL ZERO SET 5 26 The meter is properly zero set when the pointer rests over the zero...

Page 32: ...TM11 6625 1576 15 Section V Model 333A 334A Figure 5 8 Figure 5 8 Component and Adjustment Location 5 8 ...

Page 33: ... Figure 5 9 g Repeat steps b through f adjusting A3R30 in stead of A3R16 5 29 BRIDGE BALANCE ADJUSTMENT C3 MAINTAIN THE LEAD DRESS TO C3 AND TO THE TUNING CAPACITOR C4 ANY CHANGE IN LEAD DRESS WILL CAUSE A CHANGE IN CAPACITANCE a Connect the Test Oscillator to the Distortion Analyzer b Set the Distortion Analyzer controls as follows FUNCTION Selector SET LEVEL METER RANGE Switch SET LEVEL Range FR...

Page 34: ...er meter indication of 0 9 on the 1 0 scale 5 10 d Adjust the frequency response test set meter control for a set level indication e Change frequency response test set frequency t 20 cps f Readjust the amplitude until the frequency re sponse test set meter indicates set level g The Distortion Analyzer meter shall indicate 0 9 5 NOTE If reading exceeds these limits change A2C25 Typical value for th...

Page 35: ...F THE INSTRUMENT AVOID TOUCHING ANY OF THESE CIR CUITS WITH THE BARE FINGER AS SKIN OILS ARE EXTREMELY CONTAMI NATING IF HANDLING IS NECESSARY WEAR CLEAN COTTON OR RUBBER GLOVES DO NOT USE A PENCIL TO TRACE CIRCUITS IN THE INSTRUMENT GRAPHITE PENCIL LEAD IS AN EX TREMELY GOOD CONDUCTOR AND MN ACCIDENTLY INTRODUCED PATH OF THIS TYPE IS SOMETIMES DIFFICULT TO LOCATE TO AVOID SURFACE CON TAMINATION O...

Page 36: ...TM 11 6625 1576 15 Section V Table 5 8 Model 333A 334A 5 12 ...

Page 37: ...nent lead hole by heating the hole with the iron and inserting a wooden toothpick Re move the toothpick after the solder has cooled and insert the new component lead d To replace components shape new leads and insert them in lead holes Reheat with soldering iron and add a small amount of new solder as required to insure a good electrical connection e Clean excessive flux from the connection and ad...

Page 38: ...TM 11 6625 1576 15 S e c t i o n V T a b l e 5 9 Model 333A 334A 5 14 ...

Page 39: ...Figure 5 10 Troubleshooting Logic 5 15 S e c t i o n V Figure 5 10 T M 1 1 6 6 2 5 1 5 7 6 1 5 ...

Page 40: ...Figure 5 11 Frequency Tuning Assembly 5 16 Model 33A 334A Section V Table 5 10 TM 11 6625 1576 15 ...

Page 41: ...ic diagram An A5 board component location diagram is included wiring data and A5 board component location diagram because the A5 components are not identified on the for the 33A and 334A Distortion Analyzers The sche prlnted circuit boards A partial interconnecting matic diagram illustrate the circuits contained within diagram is also included to assist in reconnecting each assembly as well as the...

Page 42: ...6 2 Figure 6 1 P O Internal Wiring Data Section VI Figure 6 1 Model 333A 334A TM 11 6625 1576 15 ...

Page 43: ...tant General HAROLD K JOHNSON General United States Army Chief of Staff Distribution Active Army USAMB 1 USACDCEC 1 USACDCCEA 1 TOAD 6 USACDCCEA LEAD 8 Ft Huachuca 1 NG None USAR None For explanation of abbreviations used see AR 320 50 U S GOVERNMENT PRINTING OFFICE 1990 0 262 912 30346 SAAD 5 Eighth USA 5 ...

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Page 53: ...PIN 016265 000 ...

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