Dumont 183 User Manual

Du Mont

CIRCUIT ARRANGEMENT

A simple straight line layout is used in these

the receiver is installed under the operating conditions

imposed by the .earth’s magnetic field. and the power

supply line voltages. Once properly set these controls do

not need adjustment and since they. were not provided for

the owner’s use we suggest that the dealer or serviceman

seal the back of the cabinet as it is not possible to tamper

with the controls when the back is in place. The use of the

parts and tubes shown in Fig. No, 1 and Fig. No. 2 can be

checked by comparing the "V” numbers, etc., with the

schematic drawings which are furnished in the back of

this manual. Four separate schematic drawings have been

provided which, due to their size, will be found more

readable than a single drawing.

receivers that should prove extremely helpful to the

serviceman. Viewed from the front, the video receiver is

on the left side of the chassis and the sound receiver is on

the right. Fig. No. 1 shows the front controls and the

sound receiver while Fig. No. 2 shows the rear

adjustments and the video receiver. The top portion of the

chassis contains both sweep circuits along with the

modulating circuit of the cathode-ray tube. To prevent

confusion each side is considered separately, half

appearing in Fig. No. 1 and the remainder in Fig. No. 2.

The seven auxiliary controls shown in Fig. No. 2 are

provided for the use of the installer and serviceman.

These controls are necessary to make the final alignment

of picture size and positioning when

CAUTION AND WARNING

The set is equipped with a safety switch which

automatically opens upon the removal of the back of

the cabinet. This protects the operator from dangerous

high voltages which would otherwise be exposed.

Large cathode-ray tubes operate at high-voltages and

hence are evacuated to a very high degree of vacuum.

Therefore the atmospheric pressure on the glass can run

into tons depending on the size of the tube. A collapse

therefore is as bad as an explosion and all cathode-ray

tubes should be handled with care. The Du Mont

Laboratories have gone to great expense to provide a

cathode-ray tube that is safe for the home and the

structural design results in its ability to stand tests nearly

twice as severe as usually employed. The serviceman,

however, should observe the following rules as he will

probably be the only one to handle the average tube.

The serviceman that is engaged installing or

servicing television receivers is urged to take all

precautions and run no unnecessary risks. The high

voltages that are necessary with this type of equipment

are very dangerous and should not be approached in a

careless manner.

1. Be careful in handling the tube.

It is better to shut the set completely off between

adjustments than to suffer a painful or even a

dangerous burn.

2. Watch the use of tools near the tube.

3. Don't scratch the surface of the glass.

4. Don’t stand the tube on a metal surface or in any

other way cause certain parts to be quickly

heated or cooled.

Du Mont

INSTALLATION OF RECEIVER

Antenna Installation

Location of the Antenna

In the installation of television receivers the proper

antenna is a necessity. Successful installations will result

from attention to details, while slipshod and careless work

will bring only poor customer satisfaction and repeat

calls. There is nothing difficult about the installation of

television aerials, a little patience and experience is all

that is required. Regular broadcast aerials in the majority

of cases will be found useless. Impress this upon the

owner and make a satisfactory installation regardless of

what other equipment he already has. Satisfactory picture

reception is what both of you require for the completion

of the installation.

Whenever possible the Dipole should be erected so

that it is in line of sight with the transmitter. This does not

mean that no signals can be secured where a direct view

of the transmitter cannot be obtained. Surprising results

are often secured on these high frequencies and no

concise rules can be assigned to this work. If the location

is on a street, having heavy traffic there may be

considerable noise level due to automobile ignition

systems. In this case, locate the Dipole to the rear of the

building and away from the source of the noise as far as

possible. In the case of' electrical machinery over which

you have no control, the same method can be employed

along with the utilization of the directional effects of the

aerial which will be covered later.

The Dipole Antenna

The Dipole form of aerial is generally satisfactory; it

consists of two metal rods, each approximately five feet

long and placed on a line with each other. Extreme

accuracy in the length of these rods is usually not

necessary and if the receiver is located very close to the

transmitting station it may be found advisable to cut down

the length of each rod. The simple dipole aerial is shown

in Fig. No, 3.

Room Illumination

Whenever possible the receiver should be so placed

in the home that a direct glare from either natural or

artificial light does not fall upon the face of the cathode-

ray tube. The received picture may be viewed under a

variety of conditions where it is not always convenient to

darken the room completely. Adjustments made to meet

these conditions will not cause damage to the receiver.

Viewing the pictures in as dark a room as possible is

always at an advantage as it permits the setting of the

Intensity and Contrast controls in a manner that will give

picture tone values more correctly relating to those

actually used in the studio from which the picture is

transmitted.

The Lead-In

The most popular lead-in from the dipole to the

Television receiver will be a twisted pair as it is

inexpensive and generally satisfactory in locations where

the. signal is strong. The length of this lead is usually not

of extreme importance, It is best to get the Dipole located

in the clear and as. far from electrical interference as

possible than to limit its location by using a theoretical

exact length feeder, The twisted pair should be soldered to

the lugs on the Dipole as a good connection is essential

and necessary since several changes in the position of the

antenna may be required for best results. The other form

of lead-in is the coaxial line such as the Amphenol No.

72. This form of feeder should be used in installations

where the length of the lead-in is too long for satisfactory

work with the twisted pair and again where the

installation is at an extreme distance and every bit of

energy picked up must be delivered to the receiver.

Installation Process.

It is a good plan to proceed as follows with the

installation,

l. Erect the Dipole antenna in the clear. Start by using

horizontal polarization (mount the rods horizontal) and

turn them until their plane is at right angles with the

location of the transmitter

2. Adjust the receiver to produce a picture.

3. Return to the antenna and make final adjustments for

best signal strength and removal of ghosts, etc.

Ghost Effects

Polarization

Where the picture appears to be duplicated and

slightly displaced, the additional picture is referred to as

a ghost. This effect is usually due to the refection of the

signals and can be cured by the slanting or rotating of the

Dipole or the use of a reflector or reflectors. If after all

possible positions have been tried, the ghost still exists it

will be necessary to change the location of the antenna

and try again.

If the dipole is mounted horizontally it is said to be

horizontally polarized, and if vertical it is vertically

polarized. Since the physical location materially effects

the aerial no specific form can he advised and we can

merely suggest that you start by using horizontal

polarization and change if necessary to produce the best

results.

Du Mont

Directional Effects

4. Marked INTENSITY

The intensity or brightness of the picture is controlled by

this knob. It should be adjusted in conjunction with

Control No. 1 to get the best picture. Note: it is a good

plan to retard (turn to the left) this control when starting

the set. If about 15 seconds is allowed to elapse before

advancing this control it will prevent a small bright spot

from appearing on the screen which might eventually

darken the screen.

In the simple Dipole, directional effects are not very

pronounced, but it does have a rather sharp no-signal

radius and it is possible in some instances to materially

reduce interference by placing the offending source in this

area. If the installation of the receiver is being made at

quite a distance from the transmitter or if the signal level

is very low due to local conditions it is well to consider

the use of a reflector. This is done by placing a rod, about

ten feet long, parallel with the Dipole and about 5 feet in

back of it. The directional effect of the Dipole remains the

same, namely at right angles to the plane. Signals coming

from the front will be greatly increased. In using

reflectors it is well to bear in mind, however, that any

signal approaching from the rear (where the reflector is

located) will be greatly attenuated. Fig. No. 4 shows

reflector added to the simple Dipole.

5. Marked FOCUS

This control is used to sharpen the individual lines of the

pattern and once set seldom requires further adjustment.

6. Marked VOLUME

This volume control adjust the audio volume and has no

effect whatever upon the picture

Rear Controls of the Receiver

Operating Controls of the Receiver (Front)

As previously stated the adjustment of these controls is

necessary for the final alignment of picture size and

positioning, as the earth's magnetic field and power

supply line voltages vary with locations. The location of

these controls is shown in Figure No. 2 and their use will

be covered in numerical order. Proceed as follows:

remove the wood screws holding in the back of the

cabinet and pull out the back. The safety switch will open

turning the set off and since it is necessary to have the set

in operation while making these adjustments the switch

can be made temporarily inoperative. (A large battery clip

is convenient for this purpose.) Do not reach into the set

with the voltages on. (See Cautions and Warning.) There

is one adjustment that cannot be made by these controls,

that of rotating the Cathode-ray tube to cause the picture

to properly line up with the viewing opening. To remedy

this, turn the set off, remove the elastic band that grips the

rear support and rotate the tube by hand in the correct

direction.

First, become familiar with the controls on the front of the

receiver. Since the receiver has been tested before

shipment, probably only a few minor adjustments will be

necessary. Therefore before touching the adjustments in

the rear attempt to operate the set according to the

instruction sheet supplied the purchaser and make only

the adjustments required. These instructions are repeated

here to cover the possible lose of the sheet. Figure No.1

shows the front of the receiver with the controls

numbered and the use and the purpose of these controls is

as follows.

1. Marked CONTRAST, ON and OFF

This is a power switch for starting and stopping a set. It

also is the volume control of the picture signal. It should

be adjusted in conjunction with the intensity control (No.

4) to produce a picture of pleasing contrast to the user. If

the location is such that the signal received is very small it

may be necessary to use the full gain of the control, while

in a good location it may, have to be retarded

considerably. If the picture is not satisfactory the rear

controls must be adjusted as covered in a following

section.

The function of the seven rear controls are as follows

1. Vertical Frequency Control

This controls the frequency of the vertical sweep. If the

picture is not steady and slips past at intervals, vertically,

this control should be adjusted until a steady picture is

secured.

2. Marked SELECTOR

This control is a four position switch provided for

covering four television channels. The present alignment

was given previously under the technical information

section.

2. Vertical Size Control

If the picture is too narrow and out of proportion

vertically this control will remedy the trouble.

3. Marked TUNING

3. Vertical Positioning Control

Only one control is necessary to properly tune both the

sight and sound channels. Simply adjust this control until

the best reception of the sound is secured and at this point

the picture signal will be correctly tuned.

As its name indicates, this Control will move the pattern

vertically, allowing the picture to be placed directly in the

center of the opening.

Du Mont

4. Astigmatic Positioning Control

If no picture can be secured but modulation (dark and

light spaces) can be seen on the screen, the setting of the

horizontal frequency control is probably incorrect. Adjust

this control until the picture forms.

This is adjusted in conjunction with Control No. 5 to

give the best possible focus on the corners of the picture.

5. Horizontal Positioning Control

This control positions the picture horizontally.

6. Horizontal Size Control

The width of the picture is adjusted by this control.

7. Horizontal Frequency Control

With the adjustment of these controls the installation

should be satisfactory. However, if the signal is weak or if

ghosts or noise is present, return to the dipole antenna and

make changes as previously suggested until the best

position for it is secured.

SERVICE

While the technique employed in servicing television

receivers is similar to ordinary radio practice, there is a

greater need for basic knowledge and the time will be

well spent that is used to study the fundamental principles

of television before attempting actual service work. For

obvious reasons it will be impossible to include

fundamental theory in this manual, however, since very

little data concerning the form of sweeps used in these

receivers is available, the following description may be

helpful.

Fig. 5 is a schematic diagram showing synchronizing,

signal separation and sweep circuits used in this receiver.

The two 6J7G tubes (V18 & V22) function as the

synchronizing signal separators. The outputs of the two

plates are fed their respective synchronizing windings of

the horizontal and vertical oscillation transformers. Linear

sawtooth deflection is effected using a 6AD5G triode as

an oscillator and a 6R6G triode as an amplifier.

Oscillations are generated as follows:

Let us consider first the low frequency vertical circuit.

Condenser C76 is charged from the power supply through

the resistor consisting of R64 and R65. R65 functions

mainly as an amplitude or size control, although it has

some effect upon the frequency of operation. Condenser

C76 charges to practically full power supply potential. As

a result of previous oscillations, a charge on condenser

C75 is held on the cathode, which gradually decreases to

zero through R59 as C76 is charging. This charge on C75

is high enough to hold the tube at cutoff. The grid of the

tube is at D.C. ground potential. As the cathode

approaches ground potential due to the discharge of C75

the 6AD5G triode becomes conducting. As plate current

flows C76 is discharged producing the return trace of the

sawtooth. The surge of plate current through the winding

of the oscillation transformer induces a voltage in the grid

winding of proper polarity to drive the grid more positive,

thereby reducing the plate circuit impedance and therefore

the return trace time. At the same time that C76 is

discharging,

C75 is charging to its initial value to cut off the flow of

plate current. As this action takes place, the plate current

surge decreases thereby applying less positive voltage to

the grid and increasing its cutoff action. Ultimately, the

tube is completely cutoff, the cathode is at its full positive

potential, and the charging cycle again begins. Resistance

R59 functions as both an amplitude and frequency control

since it determines the breakdown potential and the

frequency of recurrence of the oscillations in the plate

circuit of the triode. Synchronizing pulses are injected

into the grid of the oscillator tube through the winding of

the oscillator transformer. These synchronizing pulses are

polarized so that they drive the grid in a positive direction

with respect to the cathode and therefore hasten the

“breaking down” of the oscillator tube and effect

synchronization. Since condenser C76 is charged to

nearly full power supply voltage, the signal which is taken

from the plate circuit of the triode is extremely non-linear.

It is applied, however, to one plate of the deflecting pair

in the cathode-ray tube. At the same time it is divided by

a capacity-resistance network and is applied to the grid of

the 6R6G triode. This triode section is so operated that its

output is distorted in a manner opposite to that distortion

introduced by the non-linear operation of the oscillator

triode. The output of the 6R6G is applied to the other

deflection plate of the pair and the deflection from this

signal is such that the resultant deflection is linear.

Since the high frequency or horizontal sweep

operates in the same manner it will be unnecessary to

repeat the above description. The horizontal circuit is,

however, a little more critical than the vertical and it is

absolutely essential to keep the stray circuit capacities of

the horizontal oscillator and amplifier at a minimum in

order to keep the return trace time at a minimum.

Therefore, if repairs are ever necessary on this circuit care

must be taken not to increase the capacity of the circuit.

Du Mont

In Fig. 6 the use of a copper oxide rectifier and neon

lamp can be explained as follows. The D.C. component

necessary for background level, is introduced by the

action of the copper oxide (Westector) V24. The neon

lamp V23 is provided to protect the rectifier from high

voltage surges when the equipment is first turned on.

Assuming that the controls are properly

set and handled, the first step will be to determine the

location of the trouble and isolate the defective portion. In

this you will be aided by the design of the receiver, for, as

previously pointed out, the various sections are separately

located.

The following brief outline, while by no means

complete, will serve to point out possible causes and

location.

LOCATION OF TROUBLE

POSSIBLE CAUSES

FAULT

No picture.

1. Power supply trouble in any or all three sources.

2. Too much bias on modulator electrode.

3.Defective cathode-ray tube.

No Scanning.

No modulation.

Poor focus.

1. Trouble in 1500 volt power source.

2. Poor connections to deflection plates.

3. Defective scanning circuits.

4. Defective cathode-ray tube.

1. Defective or .shorted antenna.

2. Defect in video receiver.

3. Too much bias on modulator electrode.

4. Defective cathode-ray tube.

1. Improper voltages supplied cathode-ray tube.

(check entire divider circuit)

2. Defective video receiver.

3. Poor adjustments.

4. Defective cathode-ray tube.

Uneven brilliance.

Distorted picture.

1. Hum from power source.

2. Defective scanning circuits.

3. Scanning picked up by modulator circuits.

4. Screen burnt or discolored.

1. Poor synchronizing (circuit or adjustment)

2. Overloading (contrast control advanced too far)

3. Defective video receiver.

4. A.C. hum.

5. External interference.

1. Poor synchronizing action.

2. Leakage.

3. Varying voltages to cathode-ray tube or receiver.

4. Unsteady receiver.

Unsteady picture or flickers.

Double image.

5. Antenna loose or shorting.

1. Scanning circuits incorrectly adjusted.

2. Ghost images due to reflection of signals.

Cathode-ray tube controls

effect the picture and scanning.

1. Cathode-ray tube defective, probably leaking and going soft.

Superimposed pattern on the

picture.

1. Oscillation probably in the receiver.

Streaks across picture.

1. Usually local interference such as ignition or diathermy.

Du Mont

While no fast rule can be laid down, once the section

failing has been decided on it will generally be found that

a systematic check correctly interpreted will locate the

fault. A voltage check of the suspected circuit along with

the checking of the tubes employed will probably be the

next step. Then, if the voltages are correct and cathode-

ray oscillograph is available it can be used to trace the

source of the trouble.

At this point several factors affect our procedure and it

will be necessary for us to divide the service field into

two classes which we will call the Field and the

Laboratory. The factors in question are as follows: First,

considerable special equipment will be needed. Second,

not all of it is readily available. Third, due to the amount

of investment required the division between Field and

Laboratory must be decided by the service organization

contemplating television work.

size of various resistors and it should have a range that

includes the high resistance values (see the component

parts list).

A good voltmeter is also of value and it too should have a

high range. The Weston Model 722 can be used, thus

combining both of the above instruments. This meter is

now equipped with safety prods (good insulation is a

necessity where high voltages are checked). Sensitivity of

20,000 ohms per volt is provided along with a range of

5,000 volts which adds to the uses of the-instrument. A

unit called the Televerter is available to present owner's of

the Model 772 which will provide the high voltage range

and safe test prods.

Regarding the oscillograph, several models are available

and no particular one will be stressed for this section. The

matter of price is usually paramount with the field group

and it is well to bear in mind that the more extensive the

range the more uses to witch the oscillograph can be

applied.

Field Service

Most servicemen and: dealers will come under this

classification at present. Until improved methods and

inexpensive equipment can be developed we advise this

group to confine their work to the actions covered by this

manual and not attempt adjustments of the critical circuits

which require special equipment. It is quite probable that

the majority of service problems will fall within this range

in spite of this limitation, as the correct adjustment of the

regular control knobs along with the replacement of tubes

and parts will provide the answer to nearly all troubles. It

is recommended that the adjustment of the trimmer

condensers in all circuits be left to the laboratory group

which should have the necessary equipment for a

complete job.

Another useful piece of apparatus is the Ultra High

Frequency Oscillator. It should have the following

features in order to justify its purchase or construction.

Calibration and reliability are just as important as its

covering the entire band of television frequencies and

fundamental frequencies (not harmonics) should be used.

Provision for external modulation will be convenient,

especially if it is capable of handling television

frequencies. Internal 400 cycle modulation is essential.

Battery (self contained) operation will aid portability and

is an advantage. The Weston Model

787 will be found to possess these characteristics. The

value of this equipment can .be judged by the following

uses. Being portable it can be set near the antenna. and

used to check the antenna and feeders for actual

Equipment (Field)

operation. Using internal 400 cycle modulation, the

receiver can be checked on both the video and audio

channels. The video modulation can be roughly checked

using the internal 400 cycle source, but due to the fact that

the modulation is sine in character the black bars

produced will taper off gradually each side of the center.

The use of- a square wave signal applied externally will

be necessary if even color, sharp cut bars are desired. This

checks not only the modulation circuit but the sweep

linearity.

Regular service tools.

Regular service oscillator.

Ohmeter.

Voltmeter.

Oscillograph

Ultra High Frequency Oscillator.

Diode equipment for oscillograph or a vacuum tube

voltmeter

Discussion

Regarding diode equipment for use with an oscillograph

or its substitute, the vacuum tube voltmeter, it is advisable

to be sure that they will operate at the high television

frequencies before purchasing. If usable, either of these

units, will prove a valuable aid in locating the point where

a signal is lost or diminished.

In addition to the regular service tools the regular service

oscillator will be found helpful in checking the audio I.F.

if it covers three megacycles. Incidentally the audio

receiver is so like the average high fidelity broadcast

receiver little trouble should be experienced in servicing

this section.

An Ohmeter is convenient for checking the

Du Mont

Equipment (Laboratory)

The Type 204B High Frequency Square Wave

Generator has the following features. Two ranges of

square waves generated internally or externally are

provided. Range No. 1. 7 to 50 kilocycles continuous.

Range No. 2. 50 to 500 kilocycles continuous.

Ranges can operate separately or simultaneously. A 1

to 10 megacycle continuous sine channel is provided.

Each channel can be synchronized externally or

internally or locked with the 204-A unit. Impulse waves

are available from any square wave. The output is

approximately 10 volts peak to peak at an impedance of

5,000 ohms. Some of its many uses are as follow:

In addition to the equipment recommended for the field

group the following items are suggested.

Du Mont Type 202 Phasmajector Television Signal

Generator.

Du Mont Type 204A Low Frequency Square Wave

Generator.

Du Mont Type 204B High Frequency Square Wave

Generator.

1.Testing overall frequency and phase response of a

television receiver.

2.Testing ghost response.

3.Measuring resolution of cathode-ray tubes.

4.Adjustment of linearity of horizontal sweep.

5.Production of interlaced synchronization for testing

interlace and rasters. Useful for controlling the

Type 202 Television Signal Generator.

6.Testing synchronizing separator circuits.

Du Mont Type 207 Modulated High Frequency

Oscillator.

Du Mont Type 205 Oscillograph.

Laboratory Type Signal Generator.

Discussion

The Type 202 Television Signal Generator combined with

a small oscillator such as the Weston 787 will provide a

source of signals at all times, making work independent of

the local television transmissions. A test pattern is

therefore available at all times and for serious work it is

superior to pictures.

The Type 204A Low Frequency Square Wave Generator

has the following features. It provides an internal range

of from 3 cycles to 8 kilocycles continuous. It can be

driven externally over a range of from 3 cycles to 15

kilocycles. External synchronization is provided for and it

also has a 60 cycle square and a 1260 cycle sine output.

Impulses in connection with any square wave can be

secured. The output is approximately 15 peak to peak

volts at an impedance of 5000 ohms. Some of its many

uses are as follows:

The Du Mont Type 207 Frequency Modulated High

Frequency Oscillator will be announced at a later date.

Since the ordinary form of wobbulated signal is of no

value due to the wide band covered in television I.F. it is

necessary to provide a special unit for getting these

response curves.

The Du Mont Type 205 Oscillograph uses the intensifier

type of cathode-ray tube which gives the added brilliance

necessary for observation of fast television traces. The

vertical amplifier has a range of from 5 cycles to 1

megacycle with a sensitivity of .1 volt RMS per inch. It is

equipped with calibrated step and continuous attenuators

and the input impedance is 1 meg ohm.

1.Testing the causes of horizontal tear-out.

2.Adjustment of vertical sweep linearity.

3.Testing synchronizing circuits in general.

4.Testing low frequency response of video amplifier.

5.Testing AVC circuits for time constant and general

behavior.

Regarding the laboratory type standard signal generator

the selection is a matter of preference, and opinions vary

in extent to such a degree that we do not feel we should

specifically suggest types or makes.

6.Testing low frequency response of sweep output circuits

CONCLUSION

The difference between completely equipped service

laboratories and television development laboratories must

of necessity be slight. Anything that will aid one will

likewise be of value to the other. It is believed that data

on the use or actual application of the instruments as

outlined under the laboratory group should be supplied

with the individual pieces of equipment. Therefore they

will not be covered in detail here.

We hope that this manual will help the average

serviceman to successfully service the majority of

receivers in spite of the limitations we have been forced to

place upon him. It is possible that within the year

equipment will be available that will remove these

limitations and enable us to write more complete service

instructions. In the meantime the service department will

be glad to receive any suggestions that servicemen feel

will add to the value of this manual.

Du Mont

RESISTOR VALUES

R – Regular

S – Special

W - Wire

Ohms

Watt

Class

Ohms

Watt

Class

100

10,000

10 meg

6,000

pot

200

201

202

203

204

205

206

207

208

209

210

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

245

246

257

258

500,000

2,000

150

pot

1 meg

5,000

400

200,000

80,000

100,000

500,000

15,000

6,000

50,000

25 meg

1.5 meg

200,000

1 meg

3,000

150

5,000

3,000

5,000

150

pot

150

5 meg

2 meg

5,000

1 meg

100,000

1,500

5,000

1 meg

1,000

25,000

400

100,000

4,000

1,000

100,000

4,000

50,000

1.5 meg

2,000

50,000

10,000

50,000

250,000

180

300,000

750,000

15,000

1 meg

750,000

100,000

10,000

35,000

100,000

1 meg

pot

50,000

250,000

40,000

50,000

3,000

10,000

500,000

200,000

Du Mont

CONDENSER VALUES

Mfd.

Volts

Mfd.

Volts

.05

.000075

.0025

.005

400

1500

400

500

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

256

257

258

259

260

265

.01

400

.001

3-30

L53

L53A

T-20

T12A

T12

T11

.04

.01

.000050

.02

.10

.25

.02

.10

.25

.0002

.000050

.01

trimmer

25.

.04

.0005

.25

.01

.04

.25

1600

1500

400

1200

1600

400

600

1000

4500

450

1500

4000

400

1500

.05

.0005

16.

400

450

400

450

400

100

104

105

106

110

200

201

202

203

204

205

206

207

208

209

210

211

212

213

.0003

.02

25.

.0002

3-30 mmf.

3-5

trimmer

variable

400

25.

.0006

50.

.0006

.01

400

.0005

.01

.0006

.01

3-30 mmf.

.0006

trimmer

400

.01

400

25.

Du Mont

TERMINAL VOLTAGES

Using Weston Model 772 20,000 Ohms per Voltmeter (with Televerter)

Grid

Tube

Vl0

V11

V12

Plate

240

190

275

115

140

190

180

170

Screen

150

l55

(Control)

-4.3

-2.3

-11.5

-----

-2.0

-3.5

-2.25

-2.0

-----

290

-----

190

180

170

185

Cathode to ground

Contrast on full

Cannot be measured at the grid of V6. Should read

–4 volts at center tap of 5Z3 high voltage winding

to ground.

140

225

-7.5

V17

V13

5Z3 filament to ground = 510 volts

5X3 filament to ground = 1600 volts

(output after L7 = 1550)

V14

2Y2 output = 3950 to 4200 (ground is positive)

(output after R88 = 3800 to 4100 volts)

The above measurements were taken with respect to ground, the following are point to point.

V21

From cathode to grid - 60 to - 160

From cathode to first anode +800 to +1600

From cathode to second anode +5000

TELEVISION TERMS

AUDIO Pertaining to the sound section of the receiver.

AMPLITUDE A term synonymous with gain or size.

AXIS In television the horizontal plane is called the X Axis and the vertical the Y Axis.

CATHODE RAY TUBE An evacuated glass tube comprised of a structure for producing and focusing a stream of electrons

upon an internal screen.

COAXIAL CABLE (OR LINE) A special cable for conveying television signals with as little loss as possible.

CONTRAST CONTROL A control on the receiver adjusting the contrast between high lights and shadows in the picture.

DEFLECTION (MAGNETIC) A system where the motion of the spot in producing the picture is controlled by magnetic

fields.

DEFLECTION (ELECTROSTATIC) A system where the motion of the spot in producing the picture is controlled by the

static action of the deflection plates.

DEFLECTION (PLATES) These plates are located inside a cathode-ray tube and provide for electrostatic deflection of the

beam.

DEFLECTION (COILS) Coils mounted externally about the cathode-ray tube to produce magnetic deflection of the beam.

DIPOLE An aerial comprised of two separate rods.

Du Mont

DOUBLE IMAGE Where two images appear separately on the screen, one of the sweep circuits is adjusted to

half its correct speed. If the horizonta1 is at fault the images will appear side by side, conversely if

the images are vertically displaced the vertical sweep is at fault

FIELD In the RMA Television System there are two fields to each frame. In other words each picture is

comprised of two fields scanning alternate lines.

FRAME One complete picture, thirty of these a second are thrown on the screen.

FRAMING CONTROL A control for centering the picture.

FOCUSING CONTROL A contro1 on the receiver to bring out definition; it actually controls the width and

sharpness of the individual 1ines on the cathode-ray tube.

FOCUSING (ACTION) This is the action of the gun of the cathode-ray tube which concentrates the stream of

electrons to a small spot. (This can be accomplished by either electrostatic or magnetic methods.)

GHOST An unwanted image in the picture which is usually caused by signal reflection.

GUN (CATHODE RAY) The structure or mount inside the cathode-ray tube that produces, accelerates and

focuses the electron beam.

HORIZONTAL TEAROUT This term describes the breaking up of the upper part of the picture, either to the

right or left. The cause is usually poor low frequency response in the sweep circuits or video

amplifier.

INTERLACING This refers to the technique of dividing the frame into two fields with displaced lines to

eliminate flicker.

INTERACTION A term usually used by designers indicating leakage or the mixing of a signal into another

circuit.

LINE A single line of the 441 comprising the television picture.

LINEARITY Means uniform rate of motion. This is required as the picture will be distorted in non-linear

portions.

MODULATION A process of applying the video signa1 to the modulating or control electrode (or grid) of a

cathode-ray tube so as to produce the lights or shadows of a picture.

PARAPHASE A term used in te1evision and English books which is equivalent to the American "push pull."

PHASMAJECTOR A tube developed by the Allen B. Du Mont Laboratories, Inc. for

generating television picture signals.

REFLECTORS Additional rod or rods placed near the antenna to reinforce signals.

SAWTOOTH A saw shaped wave of electric current or voltage employed to scan or sweep a cathode-ray tube.

SCANNING (See Sweep)

SEPARATOR The circuit used to separate the horizontal and vertical synchronizing pulses from each other

and the video signal.

SPOT A visible spot of light formed by the impact of the electron beam upon the screen.

SWEEP The action of an electron beam in tracing lines across the screen.

SYNCHRONIZATION A process of producing synchronism between circuits.

TELEVISION A general tern for the transmission or reproduction of visual images by radio.

TELETRON A receiving cathode-ray tube developed by the Allen B. Du Mont Laboratories, Inc.

VIDEO Pertaining to the picture section of the receiver or transmitter.

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