MAGNAVOX MOD.TV12 CHASSIS TV2 INTERNAL VIEW.

The MAGNAVOX MOD.TV12 CHASSIS TV2 is a simple tv chassis with all receiver functions fitted on it.

CIRCUITS DESCRIPTIONS:



The tuning circuits has a large knob potentiometers tuning system which use voltage controlled capacitances such as varactor diodes as the frequency determining elements.

Therefore a stable AFC circuit is developed:

A superheterodyne receiver having an automatic intermediate frequency control circuit with means to prevent the faulty regulation thereof. The receiver has means for receiving a radio frequency signal and mixing the same with the output of a superheterodyne oscillator. This produces an intermediate frequency signal which is coupled to a frequency or phase discriminator to produce an error signal for controlling the frequency of the superheterodyne oscillator. A regulation circuit is provided having an electronic switch to interrupt the feedback circuit when only unwanted frequencies tend to produce faulty regulation of the superheterodyne oscillator.


Power supply is realized with mains transformer and Linear transistorized power supply stabilizer, A DC power supply apparatus includes a rectifier circuit which rectifies an input commercial AC voltage. The rectifier output voltage is smoothed in a smoothing capacitor. Voltage stabilization is provided in the stabilizing circuits by the use of Zener diode circuits to provide biasing to control the collector-emitter paths of respective transistors.

A linear regulator circuit according to an embodiment of the present invention has an input node receiving an unregulated voltage and an output node providing a regulated voltage. The linear regulator circuit includes a voltage regulator, a bias circuit, and a current control device.

In one embodiment, the current control device is implemented as an NPN bipolar junction transistor (BJT) having a collector electrode forming the input node of the linear regulator circuit, an emitter electrode coupled to the input of the voltage regulator, and a base electrode coupled to the second terminal of the bias circuit. A first capacitor may be coupled between the input and reference terminals of the voltage regulator and a second capacitor may be coupled between the output and reference terminals of the voltage regulator. The voltage regulator may be implemented as known to those skilled in the art, such as an LDO or non-LDO 3-terminal regulator or the like.
The bias circuit may include a bias device and a current source. The bias device has a first terminal coupled to the output terminal of the voltage regulator and a second terminal coupled to the control electrode of the current control device. The current source has an input coupled to the first current electrode of the current control device and an output coupled to the second terminal of the bias device. A capacitor may be coupled between the first and second terminals of the bias device.
In the bias device and current source embodiment, the bias device may be implemented as a Zener diode, one or more diodes coupled in series, at least one light emitting diode, or any other bias device which develops sufficient voltage while receiving current from the current source. The current source may be implemented with a PNP BJT having its collector electrode coupled to the second terminal of the bias device, at least one first resistor having a first end coupled to the emitter electrode of the PNP BJT and a second end, a Zener diode and a second resistor. The Zener diode has an anode coupled to the base electrode of the PNP BJT and a cathode coupled to the second end of the first resistor. The second resistor has a first end coupled to the anode of the Zener diode and a second end coupled to the reference terminal of the voltage regulator. A second Zener diode may be included having an anode coupled to the cathode of the first Zener diode and a cathode coupled to the first current electrode of the current control device.

A circuit is disclosed for improving operation of a linear regulator, having an input terminal, an output terminal, and a reference terminal. The circuit includes an input node, a transistor, a bias circuit, and first and second capacitors. The transistor has a first current electrode coupled to the input node, a second current electrode for coupling to the input terminal of the linear regulator, and a control electrode. The bias circuit has a first terminal for coupling to the output terminal of the linear regulator and a second terminal coupled to the control electrode of the transistor. The first capacitor is for coupling between the input and reference terminals of the linear regulator, and the second capacitor is for coupling between the output and reference terminals of the linear regulator. The bias circuit develops a voltage sufficient to drive the control terminal of the transistor and to operate the linear regulator. The bias circuit may be a battery, a bias device and a current source, a floating power supply, a charge pump, or any combination thereof. The transistor may be implemented as a BJT or FET or any other suitable current controlled device.



Power Supply: The examples chosen are taken from manufacturers' circuit diagrams and are usually simplified to emphasise the fundamental nature of the circuit. For each example the particular transistor properties that are exploited to achieve the desired performance are made clear. As a rough and ready classification the circuits are arranged in order of frequency: this part is devoted to circuits used at zero frequency, field frequency and audio frequencies. Series Regulator Circuit Portable television receivers are designed to operate from batteries (usually 12V car batteries) and from the a.c. mains. The receiver usually has an 11V supply line, and circuitry is required to ensure that the supply line is at this voltage whether the power source is a battery or the mains. The supply line also needs to have good regulation, i.e. a low output resistance, to ensure that the voltage remains constant in spite of variations in the mean current taken by some of the stages in the receiver. Fig. 1 shows a typical circuit of the power -supply arrangements. The mains transformer and bridge rectifier are designed to deliver about 16V. The battery can be assumed to give just over 12V. Both feed the regulator circuit Trl, Tr2, Tr3, which gives an 11V output and can be regarded as a three -stage direct -coupled amplifier. The first stage Tr 1 is required to give an output current proportional to the difference between two voltages, one being a constant voltage derived from the voltage reference diode D I (which is biased via R3 from the stabilised supply). The second voltage is obtained from a preset potential divider connected across the output of the unit, and is therefore a sample of the output voltage. In effect therefore Tr 1 compares the output voltage of the unit with a fixed voltage and gives an output current proportional to the difference between them. Clearly a field-effect transistor could do this, but the low input resistance of a bipolar transistor is no disadvantage and it can give a current output many times that of a field-effect transistor and is generally preferred therefore. The output current of the first stage is amplified by the two subsequent stages and then becomes the output current of the unit. Clearly therefore Tr2 and Tr3 should be current amplifiers and they normally take the form of emitter followers or common emitter stages (which have the same current gain). By adjusting the preset control we can alter the fraction of the output voltage' applied to the first stage and can thus set the output voltage of the unit at any desired value within a certain range. By making assumptions about the current gain of the transistors we can calculate the degree of regulation obtainable. For example, suppose the gain of Tr2 and Tr3 in cascade is 1,000, and that the current output demanded from the unit changes by 0.1A (for example due to the disconnection of part of the load). The corresponding change in Tr l's collector current is 0.1mA and, if the standing collector current of Tr 1 is 1mA, then its mutual conductance is approximately 4OmA/V and the base voltage must change by 2.5mV to bring about the required change in collector current. If the preset potential divider feeds one half of the output voltage to Tr l's base, then the change in output voltage must be 5mV. Thus an 0.1A change in output current brings about only 5mV change in output voltage: this represents an output resistance of only 0.0552.



INTEGRATED circuits are slowly but surely taking over more and more of the circuitry used in television sets even B/W.
The first step, some many years ago now, was to wrap the 6MHz intercarrier sound strip into a neat package such as the TAA350 or TAA570. Then came the "jungle" i.c. which took over the sync separator and a.g.c. operations. Colour receiver decoder circuitry was the next obvious area to be parcelled up in i.c. form,  two i.c. decoder and the more sophisticated Philips four i.c. design was coming on the scene. The latter is about to be superseded by a three i.c. version in which the TBA530 and TBA990 are replaced by the new TCA800 which provides chrominance signal demodulation, matrixing, clamping and preamplification, with RGB outputs of typically 5V peak -to -peak.
To improve performance a number of sets adopted a synchronous detector i.c.-the MC1330P -for vision demodulation, which of course overcomes the problem of quadrature distortion. In one monochrome chassis this i.c. is partnered by a complete vision i.f. strip i.c., the MC1352P. In the timebase section the TBA920 sync separator/line generator i.c. has found its way into several chassis was a Texas's SN76544N 07 i.c. which wraps up the sync separator and both the field and line timebase generators has come into use. Several monochrome portables have had in use a high -power audio output i.c. as the field output stage. Audio i.c.s are of course common, and in several  chassis the Philips TCA270 has put in an appearance. This device incorporates a synchronous detector for vision demodulation, a video preamplifier with noise inversion and the a.g.c. and a.f.c. circuits. The   development to be adopted in a production chassis was that remarkable Plessey i.c., the SL437F, which combines the vision i.f. strip, vision demodulator, a.g.c. system and the intercarrier sound channel.

SGS-Aces Range
Now, from the, at the time,  Italian Development Division of SGS-Ates, comes a new range of i.c.s which SGS  will set a standard pattern for TV chassis IN 1975. How this range combines to provide a complete colour receiver is shown in Fig. 1. The only sections of the receiver left in discrete component form are the video output stages, the tuner, the a.f.c. circuit and of course the line output stage and power supplies. It will be seen that the colour decoder section is split up as in the Philips three i.c. design. The TDA1150 chrominance and burst channel carries out the same functions as the TBA560, the TDA1140 reference section the same functions as the TBA540 and the TDA1160 chrominance demodulator/matrix- ing i.c. the same functions as Philips's new TCA800. It looks therefore as if this basic decoder pattern could become widely established. The other five i.c.s in the range are common to both colour and monochrome receivers. Particularly interesting are the TDA1170 which comprises a complete monochrome receiver field timebase-for colour set use an output stage using discrete com- ponents is suggested-and the TDA440 which incorporates the vision i.f. strip, vision detector and a.g.c. circuitry. The intercarrier sound i.f. strip is neatly packed away with the audio circuitry in the TDA1190 while the TDA1180 sync separator/line oscillator i.c. is a very similar animal to the now well known TBA920. The fifth i.c., the TBA271, is a stabiliser for the varicap tuner tuning supply. The novel i.c.s in this family then were the TDA 440, TDA1170 and the TDA1190 and we shall next take a closer look at each of these.

Vision IF IC:
The TDA440 vision i.f. strip i.c. is housed in a 16 -pin plastic pack with a copper frame. There is a three -stage vision i.f. amplifier with a.g.c. applied over two stages, synchronous vision demodulator, gated a.g.c. system and a pair of video signal pre amplifiers which provide either positive- or negative - going outputs. Fig. 2 shows the i.c. in block diagram form. It is possible to design a very compact i.f. strip using this device and very exact performance is claimed. Note that apart from the tuned circuits which shape the passband at the input the only tuned circuit is the 39.5MHz carrier tank circuit in the limiter/demodulator section. The only other adjustments are the tuner a.g.c. delay potentiometer and a potentiometer (the one shown on the right-hand side) which sets the white level at the demodulator. This of course gives ease of setting up, a help to setmaker and service department alike. For a sensitivity of 200/4V the output is 3.3V peak - to -peak, giving an overall gain in the region of 82 to 85dB. The a.g.c. range is 55dB, a further 30 to 40dB being provided at the tuner. The tuner a.g.c. output is intended for use with a pnp transistor or pin diode tuner unit: an external inverter stage is required with the npn transistor tuner units generally used. discrete component video output stage; in a colour In a monochrome set the output would be fed to a design the output is fed to the chrominance section of the TDA1150 and, via the luminance delay line, to the luminance channel in the TDA1150. Also of course in both cases to the sync separator which in this series of i.c.s is contained in the TDA1180.

Field Timebase IC :
The TDA1170 field timebase i.c. is shown in block diagram form in Fig. 3. The i.c. is housed in a 12 -pin package with copper frame and heat dissipation tabs. It is capable of supplying up to 1.6A peak -to -peak to drive any type of saddle -wound scanning yoke but for a colour receiver it is suggested that the toroidal deflection coil system developed by RCA is used. In this case the i.c. acts as a driver in conjunction with a complementary pair of output transistors. The yoke current in this case is in the region of 6A. The TDA1170 is designed for operation with a nominal 22V supply. It can be operated at up to 35V however. A voltage doubler within the i.c. is brought into action during the flyback time to raise the supply to 70V. Good frequency stability is claimed and the yoke current stability with changes in ambient temperature is such that the usual thermistor in series with the field coils is not required. For monochrome receiver use the power supplied to the yoke would be 0-83W for a yoke current of lA peak -to -peak with a 1012 coil impedance and 20V supply. As the power dissipation rating of the i.c. is 2.2W no further heatsink is required. For use in a colour receiver with a toroidal coil impedance of 1.6Ohm the scanning current would be 7A peak -to -peak. The power supplied to the yoke may be as much as 6.5W while the dissipation in the i.c. would be up to 2-3W. In this case a simple heatsink can be formed from a thin copper sheet soldered to the heat fins- an area of about 3-4 sq. in. should be adequate. The sync circuit at the input gives good noise immunity while the difference between the actual and ideal interlace is less than 0-3% of the field amplitude. Because of the high output impedance a relatively low value (1/iF or less) output coupling capacitor can be used. This means that mylar types instead of electrolytics can be used, reducing the problems of linearity and amplitude stability with respect to temperature and ageing. The external controls shown in Fig. 3 are hold, height and linearity (from left to right).

Complete Sound Channel:
The TDA1190 sound channel (see Fig. 4) is housed in a 12 -pin package. Possible radiation pick-up and thermal feedback risks have been avoided by careful layout of the chip. This pack also has a copper frame, with two cooling tabs which are used as the earthing terminals. The built-in low-pass filter overcomes radiation problems and with a response 3dB down at 3MHz allows for a flat amplitude response throughout the audio range: this particular feature will appeal to hi-fi enthusiasts as well since it makes the i.c. a good proposition for f.m. radio reception. The d.c. volume control has a range of 100dB. The external CR circuit (top, Fig. 4) sets the closed - loop gain of the power amplifier. The external feedback capacitor network (right) provides a.f. bandwidth and frequency compensation while the CR circuit across the output limits any r.f. which could cause severe audio distortion. The TDA1190 does not require an extra heatsink when operating in normal ambient temperatures-up to 55°C-because of the new technique of soldering the chip directly on to the copper frame that forms part of the external tabs. By doing this, SGS-Ates have reduced the thermal resistance of the device to 12°C per watt. The device can dissipate up to 2.2W at 55°C without using an external heatsink other than the printed circuit pad (about 2 sq. in.) which is soldered to the tab. The output stages of the TDA1190 are in quasi - complementary mode (with patented features), eliminating the need for bootstrap operation without loss of power. The absolute maximum output power is 4.2W with a supply voltage of 24V and a nominal loudspeaker impedance of 1612. At 12V and 812 an output of 1.8W can be achieved. Total harmonic distortion is 0.5% for 1 mV f.m. input and 2W output into 1611 at 24V. Satisfactory operation is possible over a voltage supply range of 9 to 28V, making this versatile i.c. suitable for a wide range of applications. The whole audio circuit can be mounted on a p.c.b. 2in. x 25in. without a heatsink.

Mounting: The complete family of i.c.s has been designed so that it can be incorporated in very small and simple printed circuit modules. The use of a copper frame assists in improving the thermal stability as well as facilitating the mounting of the i.c.s on the board. Where an extra heatsink is required this can be a simple fin added to the mounting tabs or a metal clamp on the top of the pack. SGS claim that insta- bility experienced with conventional layouts in colour receivers has been eliminated provided their recommendations are observed.

Power Supplies:
A simple power supply circuit without sophisticated stabilisation can be used. The requirements are for outputs ranging between 10V and 35V with adequate decoupling and smoothing. It was  possible to provide only three supply lines to feed the whole receiver system-plus of course the high- voltage supplies required by the c.r.t. The power supply requirements are simplified since the TDA1170 incorporates a voltage regulator for its oscillator, the TDA440 incorporates a regulator for the vision i.f. strip and the TDA1190 a regulator for the low -voltage stages and the d.c. volume control.
TDA1170 vertical deflection FRAME DEFLECTION INTEGRATED CIRCUIT

GENERAL DESCRIPTION f The TDA1170 and TDA1270 are monolithic integrated
circuits designed for use in TV vertical deflection systems. They are manufactured using
the Fairchild Planar* process.
Both devices are supplied in the 12-pin plastic power package with the heat sink fins bent
for insertion into the printed circuit board.
The TDA1170 is designed primarily for large and small screen black and white TV
receivers and industrial TV monitors. The TDA1270 is designed primarily for driving
complementary vertical deflection output stages in color TV receivers and industrial
monitors.
APPLICATION INFORMATION (TDA1170)
The vertical oscillator is directly synchronized by the sync pulses (positive or negative); therefore its free
running frequency must be lower than the sync frequency. The use of current feedback causes the yoke
current to be independent of yoke resistance variations due to thermal effects, Therefore no thermistor is
required in series with the yoke. The flyback generator applies a voltage, about twice the supply voltage, to
the yoke. This produces a short flyback time together with a high useful power to dissipated power
ratio.

1. A transformerless output vertical deflection circuit, comprising a vertical oscillator circuit for generating a vertical pulse train in response to vertical synchronizing pulses applied thereto, a sawtooth signal generator for generating a series of sawtooth signals, each cycle of said sawtooth signal including a pulse component, a vertical output circuit coupled to said sawtooth generator for amplifying said sawtooth signal including said pulse component and loading a vertical deflection coil, and stabilizing means connected between said vertical oscillator and said sawtooth signal generator for varying the width of the pulse component which is to be fed to said vertical output circuit in response to the average level of DC output voltage fed from the vertical output circuit. 2. A transformerless output vertical deflection circuit claimed in claim 1, wherein said stabilizing means comprises a control circuit means for receiving a series of pulses from the vertical oscillator and a feedback signal from the vertical output circuit and for varying the width of the pulse which is to be fed to the vertical output circuit in response to a DC control signal proportional to the width of the pulse component included in the vertical output signal and smoothing circuit means connected between said vertical output circuit and said stabalizing means for smoothing said feedback signal. 3.

A transformerless output vertical deflection circuit claimed in claim 2, wherein said control circuit comprises a charging capacitor which is parallel to a transistor, said transistor being switched on in response to pulses fed from the vertical oscillator wherein said capacitor is charged by the voltage fed from said smoothing circuit, and discharged in response to conduction of the transistor, a differential amplifier circuit which receives the voltage on said capacitor and a fixed voltage, and a gating circuit for producing a pulse which has a width equal to the difference between the width of the pulse fed from the vertical oscillator circuit and the width of pulse fed from the differential amplifier circuit. 4. A transformerless output vertical deflection circuit claimed in claim 2, wherein said control circuit comprises a capacitor which is charged by a fixed power source and is discharged by means of a switching transistor operated by the pulses fed from the vertical oscillator circuit and a differential amplifier circuit receiving the voltage on the capacitor and the output of said smoothing circuit. 5. A transformable output vertical deflection circuit comprising a vertical oscillator for generating a vertical pulse train in response to vertical synchronizing pulses applied thereto, a sawtooth signal generator for generating a series of sawtooth signals each cycle of said sawtooth signal including a pulse component, a vertical output circuit for amplifying said sawtooth signal including said pulse component and loading a vertical deflection coil, and pulse stabilizing means coupled between the vertical oscillator circuit a

nd the sawtooth signal generator, said stabilizing means comprising a capacitor which is charged by a fixed power source and discharged by means of a discharging means operated in response to the vertical pulse fed from the vertical oscillator, a circuit means for generating a train of output pulses each starting at the time when the voltage appearing on the capacitor exceeds a predetermined value and terminating in synchronism with termination of the pulse fed from the vertical oscillator, and gating means for generating pulses having a width equal to the difference between the width of the pulse fed from the vertical oscillator and the width of the output pulse of the circuit means. 6. A transformerless output vertical deflection circuit, comprising a vertical oscillator circuit for generating a vertical pulse train in response to vertical synchronizing pulses applied thereto, a sawtooth signal generator for generating a series of sawtooth signals, each cycle of said sawtooth signal including a pulse component, a vertical output circuit coupled to said sawtooth generator for amplifying said sawtooth signal including said pulse component and loading a vertical deflection coil, and stabilizing means, comprising a control circuit connected between said vertical output circuit and said vertical oscillator circuit for varying the width of each pulse produced by the vertical oscillator circuit in response to a DC control signal having a value corresponding to the width of the pulse component applied to the vertical deflection coil of the vertical output circuit for controlling the pulse width of the output of said vertical oscillator circuit and thereby the pulse width of said pulse component.

Description:

BACKGROUND OF THE INVENTION

The present invention relates to a vertical deflection circuit for use in a television receiver and, more particularly, to a vertical deflection circuit of a type wherein no vertical output transformer is employed. This type of vertical deflection circuit with no output transformer is generally referred to as an OTL (Output Transformerless) type vertical deflection circuit.

It is known that variation of the pulse width of the flyback pulse produced in a vertical output stage of the vertical deflection circuit is the cause in the raster on the television picture tube, of a white bar, flicker, jitter, line crowding and/or other raster disorders. In addition thereto, in the vertical deflection output circuit where the output stage is composed of a single-ended push-pull amplifier having a vertical output transistor, an excessive load is often imposed on the output transistor and, in an extreme case, the output transistor is destroyed.

TDA2190 Complete sound channel with VCR and CCC



TDA1190 & TDA1190Z:
ONE CHIP tv SOUND SYSTEM
FAIRCHILD LINEAR INTEGRATED CIRCUITS
GENERAL DESCRIPTION - The TDA1190 and TDA1190Z are silicon monolithic
integrated circuits in 12-pin plastic power packages.
They perform all the functions needed for TV sound systems, including IF limiter-amplifier, FM detector, AF preamplifier and power output stage.

The TDA1190 is specified for 5.5 MHz (PAL) sound systems and the TDA1190Z is specified for 4.5 MHZ (NTSC) sound systems. They are constructed using the Fairchild Planar‘ epitaxial process.
They provide an output power of 4.2 W into a 16 S2 load at V+ = 24 V, or 1.5 W into an
8.0 Q load at V+ = I2 V. This performance, together with the FM-IF section characteristics of high sensitivity, high AM rejection and low distortion, enables them to be used in almost every type of television receiver. No external shielding is needed.

The basic differences between the TDA1190 and TDA1190Z are:

The TDA1190Z is designed for a larger volume control potentiometer
The TDA1190 includes one of the gain adjust resistors on the chip, while in the TDA119OZ
both are required in the external circuitry.