RCA WR-99A Operating And Maintenance Instructions Manual

SUGGESTED PRICE ONE DOLLAR

operating and

maintenance instructions

CRYSTAL-CALIBRATED MARKER GENERATOR

WR-99A

RCAIElectronic ComponentsIHarrison, N.J.07029

can provide a ground. Working with one hand in your pocket and standing on a properly insulated floor les-

sens the danger of shock.

2. Filter capacitors may store a charge large enough

to be hazardous. Therefore, discharge filter capacitors

before attaching test leads.

3. Remember that leads with broken insulation pro- vide the additional hazard of high voltages appearing at exposed points along the leads. Check test leads for

frayed or broken insulation before working with them.

4. To lessen the danger of accidental shock, discon- nect test leads immediately after test is completed.

5. Remember that the risk of severe shock is only

one of the possible hazards. Even a minor shock can place the operator in hazard of more serious risks such as a bad fall or contact with a source of higher voltage.

6. The experienced operator continuously guards against injury and does not work on hazardous circuits unless another person is available to assist in case of accident.

Safety Praca utions

ITEMS

Supplied

with

WR·99A

The metal case of this instrument is connected to the ground of the internal circuit. For proper opera- tion, the ground terminal of the instrument should

always be connected to the ground of the equipment under test. Therfoutput cable has a shield through. out its entire length which is connected to the instru- ment ground and case. It is always best to handle the cable by the insulation.

An important point to remember is that there is

always danger inherent in testing electrical equipment which operates at hazardous voltages. Therefore, the

operator should thoroughly familiarize himself with the equipment under test before working on it, bearing in mind that high voltages may appear at unexpected points in defective equipment. Additional precautions which experience in the industry has shown to' be im- portant are listed below.

1. It is good practice to remove power before con-

necting test leads to high. voltage points.

this is impractical, be especially careful to avoid accidental contact with equipment racks and other objects which

Output Cable

Warranty Registration Card

Phone Tip (Red)

1 RCA·6AF4·A

2 RCA-6U8

1 IO-Mc Crystal

1 RCA·12AT7

1 Instruction Booklet

I Phone Tip (black)

1 RCA OA2

2 RCA-6AS6

I RCA-6X4

I 4.S·Mc Crystal

Information furnished by RCA is believed to be accurate and reliable. However, no responsibility is assumed by RCA for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of RCA.

(4) 3/69

TP·WR·99A

(3)

6/67

Printed in U.S.A.

When the generator is set up as a heterodyne-

frequency meter, the frequency of an external signal may be determined quickly by feeding the signal into the WR-99A and zero beating it with the

vfo

signal.

The frequency is then read directly from the dial scale.

A slide-switch type of attenuator is used with the WR-99A to provide attenuation in continuous steps over a range of 60 db on all frequencies. A special coaxial cable is provided with the unit for coupling into the test circuit.

Circuit design and layout provide a flexible system

of modulating therfoutput. For example, when the WR-99A is used in conj unction with a sweep generator and an oscilloscope to reproduce a sweep-response curve, the 4.5-Mc crystal oscillator will modulate the output from the WR-99A to produce dual markers spaced exactly 4.5 Mc apart on the curve. With output set to the frequency of the picture carrier, for example, the second marker will appear at the point on the curve corresponding to the sound-carrier frequency. The vfo signal also may be modulated internally with both 4.5 Me and 600 cps, a useful feature for adjust-

ment and alignment of sound-if amplifiers and de- tectors. The 600-cps modulation is also used to produce a horizontal-bar pattern when the output signal is set to the frequency of the picture carrier or picture inter- mediate frequency. The 4.5-Mc output signal may be modulated with 600 cps for visual alignment of the detector.

A special socket located at the rear of the WR-99A

permits the connection of an external crystal or L-C

circuit into one of the internal calibrating oscillators. When an external frequency-determining unit is used it is possible to produce calibrating beats at intervals other than 1 or 10 Mc.

The RCA WR-99A is designed for both general service and production use. The unit measures 10" H x 13%" W x 7" D and weighs 17 pounds. The WR-99A is housed in a blue-gray hammeroid case with a satin-aluminum panel.

Description

The RCA WR-99A Crystal-Calibrated Marker Gen- erator is designed for use in alignment and trouble- shooting of black-and-white and color-TV receivers, fm receivers, and other equipment operating in the fre- quency range from 19 to 260 Mc. The WR-99A pro- vides an rf-output signal from 19 to 260 Mc in eight bands on fundamental frequencies, A wide choice of modulation facilities is provided, including 4.5 Mc, which produces dual markers on a sweep-response curve to mark the picture- and sound-carrier points

on the

curve,

An extremely versatile instrument, the WR-99A combines the functions of a marker generator, a hori- zontal bar pattern generator, and a heterodyne-fre- quency meter. The frequency of the internal variable- frequency oscillator, as well as the frequency of an external signal, may be checked with high accuracy against internally generated calibrating beats at 1- or 10-Mc intervals throughout the tuning range. The

WR-99A includes a harmonic crystal oscillator and a I-Mc oscillator which is coupled to the 10-Mc crystal oscillator for accuracy. Both these oscillators may be switched in or out from the front panel and provide audio calibrating beats from the speaker in the WR-99A. Calibration of the WR-99A may be checked at 242 intervals throughout the tuning

range,

Calibra-

tion of the instrument is straightforward; no charts are needed.

The tuning dial is specially marked with all vhf sound- and picture-carrier frequencies as well as im- portant intermediate frequencies in the 20· to 30-Mc and 40- to 50-:'\1c regions. In addition, important color-TV frequencies are also marked on the dial scales.

TV servicing, the WR·99A may be used in check. ing alignment and bandpass characteristics ofrfand if circuits and the scanning linearity of vertical-de-

flection circuits. The instrument may also be used to signal trace and trouble-shoot television receivers, and is useful in locating defective sections and stages.

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Specifications

Crystal Controlled

hg ~~

Output Voltages:

VFO Ranges " . approx. 0.1 volt rms Crystal Frequencies .. . approx. 0.05 volt rms

Tonin,.Dial Characteristics:

RF tuning-dial ratio 3.5 to 1

Attenuator:

Range of attenuation 0 to 60 db

Number of steps 12 (5 db each)

Type of attenuator Matched-Impedance Pad Output.Cable Impedance: 90 ohms IO·MC Crystal Calibrator:

Accuracy ±0.01%

Number of check points ~..................................... 24

I·MC Calibrator:

Accuracy ± 0.01%

Number of check points 242

4.5·MC Crystal Oscillator:

Accuracy ± 0.02%

Electrical

RF-Oulput Frequencies (fundamentals):

19·28 Mc 27-40 Mc 39·50 Mc SO·90Mc

75·140 Mc 140-180 Mc 170·220 Mc 20().260 Mc

Internal Modulation:

1 Mc, 10 Mc, 4.5 Mc, 4.5 Mc and 600 cps, 600 cps.

External Modulation:

From external source up to 10 Mc From plug-infundamental crystal 1 Mc to 30 Mc From plug-in L-C circuiL. 100 Kc to 10 Mc

Tube Complement:

1 RCA·6AF4A Variable Frequency Oscillator 1 RCA-6AS6 Modulator 1 RCA-6U8 Audio Amplifier 1 RCA·12AT7 10·and I·Mc Oscillator

1RCA·6US 4.5·Mc and 6OO.cpsOscillator 1RCA-6AS6 Mixer 1RCA-6X4 Rectifier 1 RCA·OA2 Voltage Regulator

Power Supply:

Voltage _ 105·125volts Frequency 50·60 cps.

Power Consumption 45 watts

Mechanical

Hei,ht ~ 10 inches Width. .. 13lh inches

Depth 7 inches

Weight 171bs.

Finieh Blue-gray hammeroid case, satin-aluminum panel

Functions of Controls

RF RANGE-Selects one of

eight rf ranges from 20 to 260 Mc. This control simul- taneously switches the inter- nal oscillator circuits and

rotates the dial drum so the corresponding frequency

scale is in view.

RF TUNING - Is a fine-

tuning control used in con- junction with the RF

RANGE

control to select the desired output frequency.

OUTPUT - The modulated or un modulated rf output from the generator is avail- able at this connector. The output connector

accommo-

dates the

rf-output

cable supplied with the instrument.

RF ON· OFF-When set to "OFF" position, removes B+

voltage from the variable- frequency oscillator and reno ders the oscillator inopera-

tive. This control must be set to "OFF" to obtain the

separate 1.,4.5-, and 10·Mc output.

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RCA Crystal-Calfbrared Marker Generator WR·99A

o IIt.(O§

0:0

RF ATTENUATION-Uti· lizes frye slide switches to provide step attenuation of the rf-output signal. When

the slide switches are placed in their "down" positions, attenuation in steps of IS, 10, or S db is provided. When the switches are set to

their "up" or "out" positions, no attenuation occurs.

Because the attenuation provided by each switch is additive, the switches may be used to provide attenua-

tion in any amount from zero to 60 db.

RF IN-External

signal is fed in here when the WR· 99A is used as a heterodyne frequency meter. This ter- minal connects to therfde-

tector. When an external signal is beat with the vfo or

1· or IO·Mc oscillator signal from the WR·99A, an audio beat note will be heard from the loudspeaker.

AF GAIN·POWER OFF- Turns power off when set to "POWER OFF" position; in- creases volume level from loudspeaker when turned clockwise.

MOD IN-External modula- tion signal to be superim- posed on the rf output from the WR-99A is fed into this terminal. The MOD IN ter-

I·

minal connects directly to the internal modulator stage.

When the RF ON-OFF control is set to "OFF" and the

CAL/MOD control is set to "600

"V",

the internal

600·cps signal is available separately at this terminal.

I I

CAL/MOD-Selects type of modulation applied internally

0 00 0 0

or externally to the rf-output

o._

signal or made available at

t=:======-=-""'=::;r"'"

the output terminal. When this control is set to "OFF", no modulation is applied. When set to one of the seven remaining positions,

modulation is as given below. NOTE: With the RF

ON-OFF control set to "OFF", any type of modula-

tion except "600""\.,", is available at the OUTPUT connector.

"10 MC CAL"-Crystal-controlled audio calibrat- ing beats are provided at 10-Mc intervals at fre- quencies which are multiples of 10 Mc throughout the tuning range of the WR·99A. Makes possible precise calibration of the variable-frequency oscilla- tor from 20 to 260 Mc.

·5·

"1 MC CAL"-Audio calibrating beats are pro- vided at I·Mc intervals at frequencies which are multiples of 1 Mc throughout the tuning range of the WR-99A. Makes possible calibration of the variable-frequency oscillator from 20 to 260 Mc.

"1 MC&EXT CAL"-When a crystal or L-C circuit is plugged into the socket at the rear of the instrument, the external unit can be synchronized with the I-Mc internal oscillator to give calibrating markers at intervals of less than 1 Mc.

audio beat signal will be heard from the speaker. NOTE: The crystal frequency must be at least 1 Mc or higher.

"EXT CAL"-When an external 1- to 30-Mc fundamental-frequency crystal is plugged into the socket at the rear of the instrument, the WR-99A will give harmonic output at frequencies which are

multiples of the crystal frequency.

"4.S MC MOD"-When the WR-99A is tuned to any frequency from 20 to 260 Mc, the 4.S-Mc modu- lation will appear as dual markers spaced exactly

4.S Mc away from the vfo marker on a sweep-re- sponse curve. When the WR-99A is tuned to a pic- ture-carrier frequency, the 4.S-Mc modulation will mark the sound-carrier frequency, or vice versa, on the response curve. NOTE: The 4.S-Mc markers cannot be heard as audio beats.

"4.S MC&600 '\., MOD"-AppJies both 4.S-MC and 6OO-cpsmodulation to the output signal. When the RF control is set to "OFF" and the CAL/MOD control is set to "4.5 MC&600~MOD", only these

two modulating frequencies are available at the

OUTPUT connector. This type of output is desirable

for use in aligning sound-if amplifiers and FM detectors.

"6OO'"V MOD"-lmposes 600-cps audio modula-

tion on the rf-output signal. When the output is tuned to the frequency of a TV picture carrier or picture intermediate frequency, the WR·99A may be used to produce approximately 6 to 11 horizontal bars on the picture-tube screen for checking vertical linearity. The 600-cps modulation is also used to align FM detectors by the "zero signal" method.

•I

GND-connects directly to chassis ground and case.

00000

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Calibration and Operation

General

Before the WR·99A is put into use, it is important that the functions of controls and uses of the con- nectors be understood. The purposes of the controls and connectors are described under "Functions of

Controls".

This section explains how to calibrate the WR·99A

and how to set up the instrument to provide an un- modulated marker signal of a desired frequency, or

.a marker signal which is modulated with one or more different modulating signals. Some important sugges- tions are also given for connecting the WR·99A to the equipment under test and to auxiliary test equipment.

Because the Applications section does not include instructions for setting up and adjusting the WR·99A, the user should first make sure he understands the operation of the instrument before using it in align.

ment applications.

WR·99A Dial Scales

The 20 to 260·Mc tuning range of the WR·99A is

divided into eight convenient tuning ranges (see Figure 2). The most-used frequencies in the inter- mediate-frequency and channel- frequency ranges are spotted individually on the scales. For example, 21.25

and 25.75 Mc are spotted on the first range and -the

intercarrier intermediate frequencies of 41.25 and

45.75 are spotted on the third range. In the TV -carrier ranges, the picture. and sound-carrier frequencies are spotted individually to facilitate alignment. All these frequency settings should be used only after the WR· 99A has been calibrated against the nearest crystal check point, as described elsewhere in this section.

(

Figure 1. IF· output

cobl.

lupplled with WI-99A.

Calibration

I·Me and IO-Mc Calibration

Calibration of the WR·99A is necessary before the instrument can be used to provide accurate marker signals. Calibration is accomplished by beating the

in-

ternal variable- frequency oscillator signal with either

1· or IO·Mc internal oscillator signals. These oscilla- tors provide harmonic calibrating signals throughout the tuning range of the WR·99A. Thus, it is possible to accurately calibrate the WR·99A at I·Mc or lO·Mc

intervals from 20 to 260 Mc.

the tuning dial is turned, beat notes other than those at 1· or 10·Mc intervals will be heard. It will be necessary to exercise care to avoid confusing these

extra beat notes with the normal calibrating beats. These extra beats are weaker than the normal cali-

brating beat notes, and are usually more prevalent on the lower ranges. The extra beat notes are caused by

harmonics of the calibrating oscillator beating with harmonics from the variable-frequency oscillator. Cali- bration procedure is as follows.

Connect the power cord to an ac outlet supplying

105·125 volts, 50·60 cps, and tum the AF GAIN con-

trol clockwise from the "POWER OFF" position. Allow

15 minutes for the instrument to reach a stable oper·

ating temperature.

1. Connect the output cable to the OUTPUT

connector.

2. Set the RF RANGE control to the desired fre-

quency range, as indicated on the dial scales.

3. Set the CAL/MOD control to the "10 MC CAL"

position.

4. Set the RF control to "ON".

5. Adjust the RF TUNING control to position the dial pointer at the desired IO·Mc calibration point on the tuning dial. A strong beat note should be heard from the speaker. Carefully adjust the RF TUNING to obtain zero beat.

6. Observe the position of the dial pointer.

the pointer does not coincide exactly with the IO·Mc cali- bration mark on the tuning dial, slide the pointer, by means of the small knob at the bottom of the pointer, to the left or right, as required, to line the pointer up

• 6 •

RCA Cryaral-Cahbrated Marker Generator WR-99A

21 22 23 24

I ! I !

! I I ! !

30 31 32 33

37 38 39

I I !

,!'.

I!'

,,!" ,!,,,!" ,!I I

,! ' I!

I!I

41 42 43 44 45 46 47 48

! I !I

,! 'I,! '

,!'

! ! !

•

G G

50 55

65 70 75 80 85 90

I!I

I I

I I !

I I

I ! III ! I

I ! I

i i i i i i

.--,--,

;-3-S

'-A._S

P-S-'

P_6_~

! '

80 90

100

110 120

130 140

I"" "'1'.""""'."""'1'1""""'.""" "' •• ,.",,,

150

160

210

C 140

I !

,,',,,!, ,,,,

,,,! '

170 190

!',,,\',,,

1\' ,,

'I'

,!,

u' ','

I ,

'.1' ,

'I' " , ,,

'1 " ' ,

, !

180

170

180

200

220

200 210

230

P-7_~ P-8-5 '_9_~ '-IO-S

,-n-s

.-I2-S '-13-'

250220

240

260

,! '

,!',,,,,,,,!I , , , , , , ,

'I' ,,,,,I"I' ,,,,,,I'I' ,,,, ,, , ,

!, I

Figure 2_ Dial scale. for WR-99A. N,ote the most-u.ed TV frequenci •• are spotted individually.

with the dial-scale calibration mark. NOTE: Leave the RF TUNING control set to the zero-beat setting while making this adjustment. The dial pointer has approxi- mately 1 inch of play, permitting correct calibration at the nearest· calibrating point.

After setting the dial pointer at the 10 MC check

point which is closest to the desired frequency, set

the CAL/MOD control to the "IMC CAL" position.

Adjust the RF TUNING control to pick up the 1 MC beat at the point nearest the desired frequency.Ifthe pointer does not coincide exactly with the 1 MC cali- bration mark on the tuning dial, slide the pointer to the left or right as required to line the pointer up with

the dial scale calibration mark. Leave the RF TUNING control set for zero beat while making this adjust- ment. The calibration is now accurate at this 1 MC point and for some distance on either side.

The WR·99A should always be calibrated at

the beat point whichisnearest to the frequency

toheused.

As an example, if it is desired to set the generator

accurately to 45.75 MC, the procedure is 'as follows:

1. With the CAL/MOD control in the 10 MC CAL position, pick up the 50 MC beat on the 39 to 50 MC dial scale. Slide the pointer,ifnecessary, to coincide with the 50 MC dial scale calibration mark.

2. With the CAL/MOD control in the 1 MC CAL position, pick up the beat at 45 MC. Slide the pointer, if necessary, to coincide with the 45 MC dial scale calibration mark.

3. The calibration is now accurate at 45 MC. Adjust the RF TUNING control so that the pointer lines up with the 45.75 MC mark on the dial.

Calibration from an External Source

The two-pin socket in the rear of the WR-99A case

(see Figure 4) connects to internal circuitry and per- mits use of an external crystal or L-C circuit in cali- brating the WR·99A at other than 1- or 10·Mc inter- vals. In addition, when the vfo in the WR-99A is made inoperative the modulating signal of the external unit is available separately at the OUTPUT connector. For example, any fundamental-cut crystal in the range from 1 to 30 Me or a Colpitts-type L-C circuit designed to operate from 100 Kc to 10 Mc, in which the point between the two capacitors is grounded, may be syn- chronized with the internal oscillator circuit. The ex- ternal unit will produce audio beat signals up to about the tenth harmonic at frequencies which are multiples of the natural resonant frequency of the crystal or L-C circuit. In addition to these two special applications, an appropriate external unit may be synchronized with

the internal I-Mc crystal oscillator to give accurate

·7.

RCA Crystal-Calibrated Marker Generator WR-99A

calibrating beats at less than I-Mc intervals. Procedure for using the external feature is as

follower

With power applied to the WR-99A and the out-

put cable connected to the OUTPUT connector, set the

control to "ON".

Set the CAL/MOD control to "EXT CAL". Turn

up theAFGAIN control.

3. Plug a fundamental-cut

to 30;Mc crystal into

the socket at the rear of the instrument case.

4. Tune the

TUNING control and note that audio-beat signals occur at intervals which are mul- tiples of the fundamental frequency of the external crystal, up to about the tenth harmonic.

NOTE:

an external Colpitts-type L-C circuit is connected in place of the crystal, ground the center of the two capacitors by means of a soldering lug to the screw adjacent to the crystal socket.

To obtain locked-in calibrating markers at less than I-Mc intervals, the same procedure used above should be followed except that the CAL/MOD control is set

to "1 MC&EXT CAL" and an L-C circuit must be used. The external L-C circuit must be an exact sub- multiple of 1 Mc to avoid the generation of an exces- sive number of intermediate beat notes. For example, an O.25-McL-C circuit can be plugged in and adjusted by means of a tunable slug in the coil to zero beat with the I-Mc crystal in the WR-99A to give O.25-Mccheck points throughout the tuning range of the WR-99A. In all these applications described above, the external crystal or L-C circuit will give sideband markers when the RF control is set to "ON". When the RF control is set to "OFF", the modulating signal is available sep- arately at the OUTPUT connector.

---

Figure 3. Rear ·iocket-for c~nnection of external crystal or

ColpiHs-type L-C circuit.

Use of 4.5-Mc Sideband Markers

When the WR-99A is set up to deliver an output sig- nal on either the picture-carrier or sound-carrier fre- quency of a TV channel, sideband markers which are spaced exactly 4.5-Mc each side of the vfo marker may be obtained by setting the CAL/MOD control to the "4.5 MC MOD" position. For example, if the WR-99A is tuned to deliver an output signal at the channel 4 picture-carrier frequency of 67.25 Mc and 4.5-Mc modulation is applied, an additional marker

win

observed on the sweep-response

curve.

at the

sound- carrier frequency of 71.75 Mc. Thi; feature facilitates checking of bandpass response curves from tuners and

the overall response of both color and black-and-white TV receivers.

Cottpling the WR-99A to the Test,Circuit

Wherever possible in alignment applications, the WR-99A should be used with a marker-adder unit, such as the RCA WR-70A RF/IF /VF Marker Adder.

Test setups which utilize marker-adder units are de- scribed in the "'Applications" section.

the signal

from the WR-99A is coupled directly into the test cir- cuit, the recommendations which follow should be observed.

The rf-output cable provided with the WR-99A should always be used for coupling the instrument to other equipment. The cable is shielded throughout its length to prevent excessive radiation of the output signal and to minimize hum pickup. The output clip should be connected as closely as possible to the point of signal injection and the ground clip should be grounded close to the injection point. When the marker is fed into the tuner, the ground should be connected to the tuner shield. Do not connect the output cable to any circuit containing B+ voltage. Failure to observe this precaution may result in damage to the WR-99A.

Figure 4. RCA WR-70A Marker Adder.

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+ 18 hidden pages

RCA WR-99A Operating And Maintenance Instructions Manual

Specifications and Main Features

Frequently Asked Questions

User Manual