Marconi Instruments TF 2337A User manual

Instruction Manual
No. EB 2337A
for
RADIO FREQUENCY INTERFERENCE
This equipment conforms with the require-
ments of EEC Directive 76/889 as to limits
of r.f. interference. E54881-0300:01
MARCONI INSTRUMENTS LIMITED
ST. ALBANS HLKUOKUSMIUC ENGLAND
M.I.
G/76 JPR
EB 2337A
1-7/76

Change No.C
EQUIPMENT ... TF 2337A
title AUTOMATIC DISTORTION METER
CODE No 52337-9 iON ,
SER. Nos Current production v
ACCOMPANYING ,
DOCUMENTS ... None
^lANUAL CHANGE '
The a.c. power connector and fuseholder types have been changed and a
line voltage selector control added on tne rear panel. Also adifferent
type of integrated circuit has been fitted in position QA 105 in the meterin
circuit.
Changes to the instruction manual are as follows:-
Chap.2, page 8
Change para. 2.2.1 to read:^
2.2.1 MAINS VOLTAGE SETTING
To adjust the mains voltage setting, determine from the label on
the rear panel the line voltage range required i.e. A, B, Cor Dand
select accordingly with the adjacent line voltage selector control.
Check also from the line voltage label that the fuse fitted is
of the correct rating.
REAR PANEL CONTROLS AND CONNECTORS
L'/oi S«lec tor
\
0-I..
...Q
c-J- -La.
F.. o'"
n.o„
Line Vo»a9e
(&0/60K2) Kum
90-II0V '
0ZA
i:j i0a-12’V
cI9L-2J’V
20'-290V
Oct. 80 Page

Chap. 6, page 32
Add below Fuse FSi 0.2 Aiap cartridge 2340]
or 0.1 Amp cartridge 23402
Fuseholder 23405
Chap. 6, page 33
Add below Connectors J5, 7.
PLA AC mains:;^OWer ii^onpector 23008
Change QA 105 to read:
QA 105,,,,,,SN.>4Ls6b'':;^^ '.28406
Chap. 6, page 35
Add below S4.
Line voltage selector 23109
CIRCUIT DIAGRAMS
Fig. 7.1
'Change power supply input circuit to- include Hpe voltage selector
panel as shown 'below:- '
Selector range Line voltage
50/60HZ
Shorting
Tapping
A90 no VM-©®,®
:B
'
' i
l0,3 -127 V' ©-©; ®>©
c: 193 237 V(D-© ®,©
D207 -- '250 V©- ©®.©
Fig. 7.3
Change QA 105 type to 74LS00,
Oct. 80 Page 2of 2

Chapter IGeneral Information
1.1 Introduction
1.2 Data Summary ...
Chapter 2Operation
2.1 Installation ... ... ...
2.2 Power Supply ... ... ... '
2.2.1 Mains Trans i'orincr Tapping
2.2 Controls ami Coiinocl inns ,...
2.4 Operation ... ... ...
2.4.1 Preparation' for Use ...
2.4.2 Level Moasurcincnl, ...
2.4.3 Distortion Measurement ..
2.5 Calibration ... ... ...
Chapter 3Technical Description
3.1 Prim!ii>lc.s of 0|H^r;i|,ion .. ... ... ...
a.<i<nin- I'H 1i(i imiiii 1V.... ... ... ...
3.3 Circuit Ucsei'ipiiun ... ... ...
3.3.1 Detailed Description of Patio Circuit ...
5
6
8
8
8
f)
9
9
10
10
10
12
\ :i
!:i
14
Chapter 4Maintenance
4. 1Introduction ... ... ...
4. 2Access ... ..,•...
4.3 Performance Checks ... ...
4. 3. 1Level Meter Accuracy ...
4.3.2 Level Meter Frequency Response
4.3.3 Band Rejection Filter ...
4.3.4 Harmonic Characteristic .
4.3.5 Distortion Meter Accuracy
4.3.G Ratio Circuit
4.3.7 Input Hesistance .. ...
4. 3. 8Input Shunt Capacitance ...
IG
16
16
17
17
18
19
19
21
21
22
TF 2337A

Chapter 5Repair
5.1 Introduction ... ... ...
5.2 Fault Location .. ... ...
5.3 Waveforms
Table 5.1 Fault Location .... ...
Table 5. 2(a) Transistor DC Voltages .
,
Table 5. 2(b) Integrated Circuits DC Voltages
5. 4Alignment Procedure ...
5.4.1 Power Supply
5.4.2 Level Zero Adjustment .
.
5.4.3 Level Gain
5.4.4 Distortion Zero .
.
5.4. 5Distortion Gain and Ratio Adjustment
5.4.6 400 Hz Band Rejection Filter ...
5. 4. 7 1000 Hz Band Rejection Filter .
.
5.4.8 Bias Adjustment .... ...
5.5 Chassis Wiring . . ... ... ...
Table 5. 3Connector Resistance Checks
5. 6Packaging for Reshipment
23
23
23
24
25
26
26
26
27
27
27
27
27
28
28
28
29
30
Chapter 6Replaceable Parts
6.1 Introduction
6.2 Ordering
6. 3Parts List
31
31
32
Circuit Diagrams
4TF 2337A

LEVEL DISTORTION
AUTOMATIC CMTOATON MtT» ni357A
RwiMn OtMortjon R„j,
"*A“X *er«t«hrt^
neasurement of both level and
rjamontal frequency rejection is
switches of the input voltage
TF 2337A Automatic Distortion Meter enables rapiu auu
.rtion, factors of audio frequency signals. The need to tune o
ded, thus operation simply cons^ists of the selection by push bi
e, distortion range and fundamental frequency.
The instrument measures distortion in the conventional
tal component and comparing the residual with that of the tot
.1 design of the ratio circuit the need for reference
hviated- Thus fluctuations of the input level (up to -10 dB) -
r»rv 'vO' "iV m
n
TF 2337A

l.l DATA SUMMARY
FUNDAMENTAL FREQUENCIES
BANDWIDTH (Upper -3 dB point)
Levei measurement
Distortion measurement
'input impedance
DISTORTION measurement
5
Range
Measurement accuracy
Mini mum iii[)ul -'icvtd
Maximum input
FILTER CHARACTERISTICS
Fundamental rejection
Harmonic frequency
response for
400 Hz filter
1000 Hz filter
LEVEL MEASUREMENT ;,,, ,
,
';Range..
'AcGuraqy,,.. ,
Frequency response
POWER REQUIREMENTS
400 Hz ±5%
1000 Hz ±5%
(optional frequencies available
on application)
20 kHz (nominally)
10 kHz (nominally)
100 IcH ±10% unbalanced:
Shunt capacity, less than' 50 pF'.
0. 01% to 30. 0% in six ranges -
0.01% to 0.1%
0.03% to 0.3%
0.1% to, 1.0%
0..3%ptO;:3:,0%, .
4, i;o#to 10%. ' u.. ..
3;-0%to 30%
±3% f. s.d. :-o.l)each range, ±2% of readini
0. Ivoll V. m. s.
100 volts r. m. s.
At least 83 dB (within ±3% of centre frequency)
At least 6G dB (within ±5% of centre frequency)
760 Hz toTO kHz withinT.6 dB.
id^jo'^lIz td'lO'kliz wR^^^^ O.GClB. :
0.03 'to K)0 volts r. m.s. in six ranges -
Ofi OU to 0.3 volts r.
0:1 to IFO •v'o'lts r.mv.s.»
0.3 to 3. 0voltS'uum'. s. .
1. 0to 10 volts r. m. s.
’3V0''td'30 volts 'r.'m. s;t't
VO to'''''l'0'0 'V'bUs'rim.sF' ,'.>
:Ej% lVsJ'd?''of ea'bh'Tangei 'U -,
Fhit'tb’within'T clB over the':band
20 Hz to 20 kHz.
95 to 125 volts or 190 to :'25.0 volts
50 to 60 Hz 6VA.
6TF 2337A

DIMENSIONS AND WEIGHT lleigT.l Wkitli Deptii Weight
210 mm 285 mm 270 mm 6kg
8. 2 in n. 2in lO.T in.. 12 lbs
TF 2337A

2.! INSTALLATION
The TF 2337A Automatic Distortion meter is available only for bench mounting. Normally set on''four
rubber feet, the instrument can be used in the tilted position by swinging the carrying handle forward
and downwards until it is positively located in tlie vertical position. The handle then acts as atilt
stand.
2.2 POWER SUPPLY
The instrument is normally supplied ready for use with 230 Va.c. mains supply. Before connecting
to the mains supply ensure that the mains voltage setting is correct and the correct mains fuse is
fitted as follows :-
Mains supply
95-125 Va.c.
190-250 Va.c.
2.2.1 Mains Transformer Tapping
Fuse rating
0. 2amps
0. 1amp
MI Part No.
FPP/2337A/23401
FPP/2337A/23402
VOLTAGt
RiNC-e SHORnNG TAPPING
•iD -lev A* 0 0 1A,y
A-0 C-P A.c
180 -'220 0--O A.i:
20'/ -2b) C-D A.r
Fig. 2.1 Mains transformer tappings
To adjust mains voltage setting proceed as follows :
(1) Remove the lop cover of the instrument by ruieasing the two knurled knobs located on
each side of the instrument.
(ii) Locate the mains transformer situated in the top right hand corner.
(iii) Check that thetapping is as illustrated in Fig, 2.1 for 230 Va.c.
(iv) If an alternative setting is required, adjust the transformer tappings as indicated in the
adjacent table.
NOTE ;An orange wire from the indicator lamp (PLl) on the front panel is connected
to the mains transformer terminal (B). This lead should not be moved as it
also supplies the 100 Vworking voltage for the neon lamp.
8I’F 2337A

2.3 CONTROLS AND CONNECTIONS ,
«>N/<
oil.
;Mc•li. ih,. h11 111 '111 I.1 i;iinii Mill iIioin iHlif'o MlifM ih.' >n)li|’l \IM''' If I'liOi !
INPUT terminals. Two terminals, one insulated for signal connection. Connection can
be made by banana plugs or spade terminals.
FUNCTION switch (S2). Four position push-butuon switch. i''be Level position ensures only
level measurements are made whereas with the 400 Hz or lOCO Hz push button selected the
Instrument will measure both level and distortion factor.
With the CAL push button selected apre -determined signal is led to the distortion
measuring circuit as a distortion calibration check.
LEVEL RANGE S'A'itch (HI). Consisting of six push buttons, selection of which will deter-
mine the full-scale range of the level fheter. Each button is calibraied in volts and dB’s.
LEVEL meter. Consists of three scales, two voltage scales in black and adB scale in red
(0 dli -T V).' ''' ^
'
'DISTOFiTION RANGE switch (H3)'.' Consisting of six push buttons, selection of whicii will
determine the full-scale range of the distortion meter. Each push button is calibrated in
full-scale distortion percentage and dB's.
DISTORTION meter. Consists of three scales, two distortion fdetor range scales in black
and one distortion scale (dB)_in red. (0 dB =100% distortion factor).
,^
^OPERATION "'co V
The followmg'instriictibns are intended' as a
Distortion Meter. However, because of the
tions will become unnecessary.
detailed guide 'to tiie oj'ieratibn'of the TE' 2337A' Automatic
units inherent simpllci^V continued use bf those instruc-
2.4.1 Preparation for use
Before commencing measurement,
:,(i) .ensure that the rnu.ms transformer ^tapping, and fuse rating aierrUtroct for the supply
in use.
TF 2337A

;ensure that the mechanical zero of both meters is correctly set. Adjustment is made
;
•using the inset screw located centrally below each meter. ;
(iii) ensure that all push buttons are in the 'out' position and that the supply switch is in the
off positioUi
fif! (iv) connect the instrument to the supply and switch on. Check that the supply indicatinE
lamp is illuminated.
The TF 2337A is now ready for use, proceed as follows :
2.4.2 Level Measurement
(i) Select the LEVEL push button of the FUNCTION switch. !
(ii) Select the 100 V(40 dB) push button of the LEVEL RANGE switch.
(iii) Connect the signal to be measured to the input terminals.
(iv) Observe the reading on the LEVEL meter. If the reading is not within the 0dB to -10 dB
scale, continue to select successively lower LEVEL ranges until the desired indication
is obtained.
(v) Note the LEVEL push button selected. The full-scale of the meter is determined by and
indicated above this push button.
If^measurement is required in dB's the signal level is determined by the sum
of the me*ter indication and the dB value indicated (in RED) above the selected push
button e.g. with the 30 dB (30 V) push button depressed and the meter reading -5 dB,
the signal level will be 25 dB above 1V.
2.4.3 Distortion Measurement
_(i) Carry out Level measurement as described in Chapter 2.4.3 (i) to (iv).
,.(ii) Select the desired fundamental filter by selecting either the 400 Hz or
1000 Hz push button.
.(iii) Select the 30% (-10 dB) push button of the DISTORTION RANGE switch. ''
(iv) Observe the reading on the distortion meter. If the indication is towards the -20 dB
end of the scale select lower distortion raises xmtil the indication can be easily read.
The meter full-scale range is indicated by the percentage figure (black) above the press
button selected.
If measurement is required in dB's, the distortion level is determined by adding the
meter dB indication (red) to the dB figure (red) immediately above the selected push button.
i. e. if the -40 dB push button of the Distortion Range Switch is selected and the meter indi-
cates -3 dB then the distortion level measured is -43 dB (0. 7%).
NOTE tThe distortion measurement is valid only if the level meter indication lies
between -10 and 0on the dB scale.
2.5 CALIBRATION
Afacility for checking the distortion measuring circuits is provided. Proceed as follows
TF 2:{37A

(i) Check that the level meter indication lies between 0dB and -10 dB as previone’y
described.
(ii) Select the CAL push button of the function switch.
(iii) The distortion meter indication should read 10 (f. s.d. on the upper range) regardless
of the distortion range selected. If the indication is in error by more than one division,
refer to Chapter 5. 2for re-alignment iristructions.
TF 2337A

Iapter^
3Teclitiical description
0——Impedincp Arrplifi*!
0——rioT) QIOt/102 QI03/I06
LEVEL METER
Ratio
Circuit _c>-/
OAt03-)05
nd QA106 DMETER
Arr^liliw AC-DC
Q110-I!3 QA506/I07
Fig. 3. 1Block Diagram TF 2337A
3.1 PRINCIPLES OF OPERATION
The method of distortion measurement is carried out in the usual way by filtering out the fundamental
component and comparing the amplitude of the residual with that of the total signal.
Distortion analysis -Distortion factor is defined by the equation -
DISTORTION
-FACTOR VV.... V
23n
where V,
V. X100%
amplitude of fundamental
Vg* Vg =amplitude of 2nd, 3rd nth harmonic
N=amplitude of noise and hum harmonics.
The method employed by the TF 2337A Automatic Distortion Meter is based on the following
approximation which, assuming adistortion factor of less than 15%, introduces no appreciable error
DISTORTION
FACTOR -V2' .V3'
.
22
V+N
n
.... X100%
12 TF 2337A

3.2 GENERAL SUMMARY
The signal to be measured is first fed to the LEVEL measuring circlets to determine the correct input
conditions for the DISTORTION measurement and to provide aLEVEL measurement ty.
^
The signal is fed via LEVEL input attenuator (SI) to impedance converter
and thence to LEVEL AC/DC converter to provide a+5. 25 voltage for full-scale defie
t:
LEVEL meter.
With the distortion measurement mode selected the signal fcom the MVEL
tar,eouslv fed via FUNCTION select switch (S2) to one of the two internal filters. The signal stripped
Sis attenuated and fed via the AC/DC converter to the -ratio* circ^t
together with the signal from the LEVEL AC/DC converter. Thus both sig^s c^be
t2 'ratio* circuit (as described in Section 3.3. 1and defined in Section 3.1) and their ratio .indicated
directly by the DISTORTION meter (M2).
3.3 CIRCUIT DESCRIPTION
LEVEL EANGE ATTENUATOR (SI). Front panel mounted 6-way push button switch consisting of one
'straight through' position and five 10 dB steps.
LEVEL IMPEDANCE CONVERTER (QlOl, 102). Large gain amplifier wi^
provides high input and low output impedance with awide band frequency Teepee. Although distortion
is low, any dlstLlon induced by the amplifier is minimized by adjustment of the bias voltage to QlOl.
LEVEL AMPUFIER (QX03 to Q106). To minimize Induced
gain and low closed loop gain. The gain is adjusted for lo. 4dB by H119 (LEVEL GAIN).
The output of this stage is also fed to the FUNCTION switch S2.
LEVEL AC/DC CONVERTER {QA101/QA102) uses diode full-wave rectification. To reduce the effects
of the non-iinearity of the rectifying circuit anegative feedback system also using diodes is mcorpor-
The d. c. output to Ml (LEVEL METER) is determined by the setting of R134 ^RU9 of the
previous stage. The d. c. output required for afull-scale deflection of Ml is +5. 2b volts.
FUNCTION switch (S2) consists of four push buttons.
With the LEVEL push button selected the output from the LEVEL amplifier to the distortion
measuring circuits is open circuited. It should be noted that although the distortion circuits
are switched out with the selection of the LEVEL push button, the level measurmg circuits
are always operative.
Selecting either of the 400 Hz or 1000 Hz push buttons, applies the total signal (suitably attenuated
by the LEVEL input attenuator) to the appropriate filter.
The CAL push button when operated applies the output from the LEVEL amp, attempted by^e
full 60 dB of the DISTORTION range switch (S3), directly to the DISTORTION amplifier. The
levels are set such that vdien the LEVEL meter reads Ml-scale the
reads full-scale. The check Is completed by reducing the input signal level by 10 dB and check-
ing that the distortion meter reading varies by no more than 1%,
FUNDAMENTAL REJECTION FILTERS are
notch characteristic as shown in Fig. 3. 2.
composed of active twin-T four stage elements having a
Two filters are fitted having fundamental rejection of
400 Hz and 1000 Hz,

DISTORTION RANGE ATTENUATOR {S3) Front Panel mounted 6-way push button switch consisting of
one ’straight through’ position and five 10 dB steps. ,
ij
-j
0
10
20
30
AHENUATtON
(dB) 40
60
60
70
80
0.5 0.7 11.5 2
FREQUENCY(f/fo)
Fig. 3. 2Fundamental rejection characteristics
of TF 2337A Filter.
DISTORTION AMPLIFIER (QUO to Q113) 54 dB gain, adjusted in the feedback circuit by R159 (DIST
GAIN).
DISTORTION AC/DC CONVERTER (QA106/QA107) similar circuit to the level a. c./d. c. converter
but differs in gain and output polarity.
RATIO CIRCUIT comprises an up-down integrator and pulse width to d. c. converter as shown in
simplified form Fig. 3.3.
3.3.1 Detailed description of Ratio Circuit
Fig. 3.3 Simplified diagram of ratio circuit.

The two signals applied to the ratio circuit are Vf derived from the Level AC/DC converter and
-Vh from the Distortion AC/DC converter. -
Switches Sa (Q107) and Sb (Q114) are reset in the open condition at time interval T(see Fig. 3.4)
by aclock triggered flip-flop QA105. Thus with Sa open the signals Vf and -Vh combine to charge
capacitor C113. When the output of QA103 reaches Vc, comparator QA104 actuates fliprflop QA105
to close Sa leaving signal -Vh to charge C113 in the reverse direction for time T-Tx (Fig. 3.4).
The flip-flop change over time Tx is therefore dependent on the relative values of Vf and -Vh.
Clock
QAI03
OAI05
OUTPUT
Fig. 3.4 Timing sequence of ratio circuit
The switching action of Sa is repeated by Sb (Q114) producing apulse, the period of which is identi
cal to T-Tx, integrated by Circuit QA108/C126/R183 and thus deriving an output voltage Vo directly
proportional to the ratio of the harmonic content of the signal and its total value (Vh/Vf). Distortion
meter (M2) indicates the value Vo.
TF 2337A 1

4.1 INTRODUCTION
This chapter contains information on performance checks and calibration procedures..
Performance limits quoted are for guidance only and should not be taken as guaranteed perfor-
mance specification unless they are also quoted in the Data Summary (Chapter 1.2).
I,n case of difficulties that cannofTSe' resolved with the aid of this manual, please contact our
Service Division at the address stated on the back cover, or your nearest Marconi Instruments repre-
sentative quoting the type and serial number of the instrument. If the instrument is being returned for
repair, please indicate clearly the nature of the fault or the work you require to be done.
4.1 ACCESS
Access to the instrument can be achieved by rotating the two knurled knobs on the side of the instrument
in the direction indicated adjacent to the knobs which will release the top and bottom panels.
4.3 PERFORMANCE CHECKS
The tests in this section may be used as aroutine maintenance procedure to verify the main per-
formance parameters of the instrument. All tests can be completed without removing the case. If
adjustment becomes necessary the appropriate procedures are detailed in the repair section Chapter 5.
Equipment required •
•f. '
•,
Instrument Required specification
Voltage calibrator AC voltage range :
100 mV to 100 Vr.m. s. e.g. ,Bradley 125C
Low distortion oscillator Frequency range :
20 Hz to 20 kHz. Distortion ^0. 01% e.g. TF 2100/1 Ml
AC voltmeter Voltage range :
100 mV to 100 Vr. m. s.
Frequency range ;20 Hz to 20 kHz \e.g. TF 2G71
DC voltmeter Voltage range :
0to ±2 volts
L-C meter Capacitance range :
0to 70 pF e.g. TF 1313A
Counter, Frequency range :
20 Hz to 20 kHz e.g. TF 2417
Switch box .See Fig. 4.
3
Resistor Resistance :100
fixed carbon film
Variable mains voltage transformer Voltage range ;
90 Vto 127 Vor 180
1%
Vto 253 V

\
4.3.1 Level Meter Accuracy
(a) Test equipment required :Voltage calibrator.
(b) Check that the instrument is correctly adjusted for the mains voltage in use as '
described in Chapter 2. 4. 1.
Set controls of the TF 2337A Automatic Distortion Meter as follows :
Function sVdtch -LEVEL
(c) Connect the voltage calibrator to the input terminals of the TF 2337A.
(d) Set the output frequency from the voltage calibrator to 1000 Hz.
(e) By using the voltage calibrator check'the level meter at f. s.d. on every LEVEL range.
The accuracy of level range should be within ±2%,
(f) Set the Level Range of the TF 2337A‘to' 1V.
(g) By using the voltage calibrator, check the scale shape of the level meter, varying the
voltage by increments of 0.1 Vfrom 0.1 Vto 1V.
The scale shape of the level meter should be within ±2% of full scale.
(h) Reduce the mains voltage by 10% and repeat steps (e) to (g). Increase the' mains voltage
to the nominal voltage plus 10% and repeat steps (e) to (g).
4.3.2 Level Meter Frequency Response
Fig. 4.1 Level Meter Frequency response cheek
(a) Test equipment required :Oscillator and AC voltmeter.
(b) Connect the TF 2337A as shown in Fig. 4.1.
(c) Set the TF 2377A controls as follows
Function switch .. LEVEL
Level range switch -IV
vd) Set the oscillator frequency to 1000 Hz, adjust the output so that the TF 2337A Level Meter
reads full scale. Note ;he oscillator output as monitored by the AC voltmeter.
(e) Keep the output from the oscillator constant and vary the frequency from 20 Hz to 20 kHz.
(0 Ensure that the frequency response of the level meter of the TF 2337A is within i3% over
the frequency range 20 Hz to 20 kHz.
TF 2337A 17

4.3.3 Band Rejection Filter
Pig. 4. 2Fundamental Rejection Filter check
(a) Test equipment required :
Low distortion oscillator ,
Counter
(b) Connect the TF 2337A as shown in Fig. 4.2,
(c) Set TF 2337A controls as follows j-
Function switch -LEVEL
Level range switch -IV
(d) Connect the output of thelow distortion oscillator to the input of the TF 2337A.
<e) Set the frequency of the low distortion oscillator to 400 Hz
the level meter of the TF 2337A to full scale. and, varying the output, set
-(f) Setthe switches of the TF 2337A as follows :
Function switch -400 Hz
'‘Distortion range switch- 0.1%
(g) Vary the frequency of the low distortion meter so that the distortion meter of the
TF 2337A indicates 0. 007%. Check the frequency at two points (+ and -) of the fundamental
frequency to confirm that the, frequency width is more than ±3%:
(h) Check that the centre frequency of the two points noted above is within ±1% of 400 Hz.
i) Select the TF 2337A controls as follows :-
Function switch -1,000 Hz.
i) Sat the output frequency of the low distortion oscillator to 1000 Hz and, varying the frequency
set the level meter of the TF 2337A to full scale.
k) Select the TF 2337A controls as follows
-Function switch -1000 Hz
Distortion rar^e switch -0.1%
l) Cany out the operation described in para. 4. 3. 3(g).
Check that the centre frequency of the two points corresponding to 0.007% distortion is within '
±1% of 1000 Hz.
18 TF 2337A

Test equipment required :
Oscillator
AC voltmeter
b) Connect the TF 2337A as shovm in Fig. 4.1.
c) Select the TF 2337A controls as follows :-
Function switcH «LEVEL
Level rang’e' Switch -IV
d) Adjust the output frequency of the oscillator to 760 Hz and adjust the output until the TF 2337A
level meter reads full-scale.
e) Select the TF 2337A controls as follows
Function switch -Press the CAL and 400 Hz push-buttons
simultaneously.
f) Note the indication of distortion of the TF 2337A, vary the frequency of the oscillator
from 760 Hz to 10 kHz.
(The output voltage from the oscillator should be kept constant.
)
Ensure that the distortion meter of the TF 2337A does not vary more than ±0.3 dB.
g) Select the TF 2337A controls as follows :
Function switch -I.EVEL
•h) Set the frequency of the oscillator to 1. 9kHz, and set the indication cf level meter of the
TF 2337A to full scale.
i) Select the following mode condition :
Function switch -Press the CAL and 1000 Hz push-buttons
simulUineously.
j) Noting the distortion reading on the TF 2337A, vary the frequency of the oscillator from
1.9 kHz to 10 kHz.
(The output from the oscillator should be kept constant.)
k) Confirm that the TF 2337A distortion indication is constant within ±0.3 dB.
4.3.5 Distortion Meter Accuracy
a) Test equipment required.
Low distortion oscillator.
Voltage calibrator.
Switch box.
TF 2337A