GRUNDIG SUPER COLOR A6681 / 96 SERIE M4020 SUPER SOUND "MONOLITH" CHASSIS CUC 220 VIEW

The Grundig CHASSIS CUC220 is a brother of the CUC720 developed for 90° degree CRT TUBE Types instead of 110° degree types.

Was first GRUNDIG TV CHASSIS (CUC220) featuring new deflection (BU208A) outputs stages and Switching power supply type and video IC TDA3560 AND TDA3561 one chip PAL DECODER, and a even new tuner unit and Main controls system was even introduced.
This here is therefore fitted with the CUC220 chassis.

 The CUC220 or generally referred CUC (Compact Universal Chassis) chassis series is fittable even in bigger models from 16 to 26 inches with few variants. The CUC (Compact Universal Chassis) is a monocarrier modular chassis completely transistorized and abandoning definitely any older technology of earlier chassis design like ancient thyristor horizontal beam deflections, complex chroma units,complex off line supply,complex tuning system,many parts . The CUC is constructed of individual plug- in modules, in which a number of generally smaller structural elements and components are enclosed, together with a printed circuit board in a unit which is generally functional in its own right and named therefore.
It has a Transistorized horizontal deflection circuits  made up of a horizontal switching or output transistor, a diode, one or more capacitors and a deflection winding. The output transistor, operating as a switch, is driven by a horizontal rate square wave signal and conducts during a portion of the horizontal trace interval. A diode, connected in parallel with the transistor, conducts during the remainder of the trace interval. A retrace capacitor and the deflection yoke winding are coupled in parallel across the transistor-diode combination. Energy is transferred into and out of the deflection winding via the diode and output transistor during the trace interval and via the retrace capacitor during the retrace interval.
In some television receivers, the collector of the horizontal output transistor is coupled to the B+ power supply through the primary windings of the high voltage transformer.

It features first time a completely new Power supply base around the "Historical" SIEMENS TDA4600;  Switching regulators serve as efficient and compact power supplies for instruments such as television receivers. A switching regulator may typically comprise a power transformer having a primary winding coupled to an input voltage source and to a power switch and a secondary winding coupled to a rectifier arrangement for developing a DC supply voltage for the instrument. A regulator control circuit generates pulse width modulated control signals that control the duty cycle of the power switch. A power switch is coupled to an inductance and a source of input voltage. A control circuit is coupled to the power switch for producing the switching thereof to transfer energy from the input voltage source to a load circuit coupled to the inductance. The control circuit is responsive to control voltages for varying the duty cycle of the power switch to control the transfer of energy to the load. A first control voltage representative of a variation in an energy level of the load circuit is developed to control the duty cycle in a manner that regulates the energy level. ; the invention relates to a blocking oscillator type switching power supply for supplying power to electrical equipment, wherein the primary winding of a transformer, in series with the emitter-collector path of a first bipolar transistor, is connected to a d-c voltage obtained by rectification of a line a-c voltage fed-in via two external supply terminals, and a secondary winding of the transformer is provided for supplying power to the electrical equipment, wherein, furthermore, the first bipolar transistor has a base controlled by the output of a control circuit which is acted upon in turn by the rectified a-c line voltage as actual value and by a set-point transmitter, and wherein a starting circuit for further control of the base of the first bipolar transistor is provided. This Power supply Provides first time all GRUNDIG Tv sets with a SMPS power supply comprising furthermore the separation from mains feature.........,

 ............. and introducing an integrated tuner IF UNIT ;The size problem is not as serious as the others although it is desirable to make a tuner compact to minimize the distances over which the low level high frequency signals must be translated. Also from a packaging point of view, a housing having a plurality of blocks each of which is surrounded by shielding partitions; a compact unit is much to be preferred and yields numerous advantages to the television stylist. These here aforementioned tuners compared to modern tuners are 200 times bigger ! Because television tuner circuits process high frequency signals at low signal levels and generally exhibit high signal gains, they are necessarily very sensitive and susceptible to oscillation and interference problems. It is thus common practice to enclose the circuitry within an electro-magnetically shielded housing.


GRUNDIG SUPER COLOR A6600 SERIE ST3020 RK  CHASSIS  CUC220  Remote control television with external data bus connection,
Remote Control With MOS IC's For TV Sets: THE GRUNDIG AV FEATURE CONNECTOR TECHNOLOGY:A television receiver is provided for use as a picture display terminal for electronic peripheral equipment, where a control system with a data-bus is built into the television receiver for multitude of commands and in which the television receiver is intended to be used in addition to the normal direct reception of televised pictures for other possible applications. The television receiver can serve as a monitor for a picture tape recorder, which is equipped for recording independently of the television receiver. A complete television receiving set is provided with automatic transmitter seeking mechanism and electronic channel storage.


1. A system for the use of a television receiver for external control of electronic peripheral devices, said television being of the type including a built-in integrated circuit remote control receiver, said remote control receiver being divided into two sections, one section being allocated to the remote control of the receiving and reproduction sections of the television receiver and the other section being allocated to a databus having nothing to do with the television receiver receiving and reproduction sections; an output terminal of said databus comprising an adaptor connector between said television receiver and an external peripheral device; a peripheral device external to the television receiver; cable means connecting the output of said databus with said peripheral device; and a decoder interposed between said databus output terminal and peripheral device for converting data from said databus into a form suitable for controlling functions of said peripheral device.

2. A television receiver as a picture terminal according to claim 1, in which said external coupling includes a connecting cable between the external connections of the television set and the peripheral device forming a unitary unit together with a decoder which transforms the data from the data collector into a code which directly controls the functions of the peripheral device.

3. A television receiver as a picture terminal according to claim 1 or 2, in which the peripheral device is a picture taping device which operates for recording independently from the television set which acts as a monitor.

4. A television receiver as a picture terminal according to claim 1, in which the functions controlled by said first commands include the on-off switching, picture, sound and channel selection of the television receiver and the functions controlled by said second commands include electronic program storage and changeover functions.

Description:

BACKGROUND OF THE INVENTION
Integrated circuits are presently known in the art for the convenient operation of television receivers, whereby the functions of on-off switching, channel selection, picture (video) and sound (audio) can be remotely controlled by the received telecontrol signal. In particular, the following function can be operated by such a system: Switching on and off of the equipment, calling for different program channels, variations and basic adjustments of sound level, brightness and color saturation, silencing of the sound as well as inserting of time references. With a known and presently available operating system up to 16 channels can be installed, so that it is possible, to select directly that number of programs and to tune the receiver to the appropriate channel.
Television receivers available today in many designs provide for up to 30 remotely controlled channels or channels controlled by the received signal (tele-signal) to properly operate. Additionally, infrared control is also becoming popular. These controls provide commands by means of a databus so that the operation of the various functions is possible with the provision of additional commands.
It is further known to equip peripheral equipment such as video tape recorders with a so-called electronic-tap-key rather than keys with a long throw so that all parts which are susceptable to mechanical wear are eliminated and replaced by digital controls.
It has become of interest to connect the peripheral equipment such as the video tape recorder to the television receiver so that both can be conveniently operated. With the development of new concepts simplification of design becomes critical for ease of operation and reduction of expense.
SUMMARY OF THE INVENTION
A television receiver as a picture display terminal for electronic peripheral devices wherein a remote control system with a data collector is installed for receiving a plurality of commands and in which only a portion of the commands is used for the remote control functions of the receiving and display portions of the television set, while another portion of the commands is used for adjusting the functions of an electronic peripheral device which may be coupled with a television set, and that the data collector is electrically coupled by means of an external coupling of the television set with the corresponding stages of the peripheral device.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a diagrammatic showing of a television receiver and electronic periphery device incorporating the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A television receiver and electronic peripheral device incorporating the invention are shown in the FIGURE. The television receiver 10 can be used as a picture display terminal for peripheral device 12. This provides the advantage, that by means of a single tele-control signal, the control of functions of the receiving and displaying sections of the television receiver can be accomplished as well as the control functions of the peripheral equipment 12, which is connected to the receiver. The peripheral device does not require a separate tele-control system since that which is already installed in the television receiver can be used. To accomplish this, portion A of the available commands A, B of the tele-control system 11 are used for the function of the television receiver 10. The remaining portion B of the available commands A, B, which is made available at databus or data collector 14 is used for the control of functions of the peripheral equipment. The databus, which is coordinated with the peripheral equipment, and which is built into the tele-control system of the television receiver, is connected electrically to external terminal 16 of the television receiver. The external terminals at television receivers and peripheral equipment are relatively inexpensive.
The primary expenses result from the necessary cable connections between the external terminals of the television receiver and the peripheral equipment, as well as the auxiliary apparatus, such as decoder 18, which decodes the data from the databus 14 and prepares it for the peripheral equipment. These expenses are reduced by simplified design, in which the connecting cables 20 and 22 together with the auxiliary apparatus or decoder 18 are combined in one component or building block. This building block can be offered as an accessory to the user of television receivers with peripheral equipment.
The invention can be used with especial advantage in connecting a television receiver with a picture tape recorder as a peripheral equipment. The picture tape recorder is equipped preferably for recording independently from the television receiver, so that the latter serves as a monitor only. With such a switching combination it is possible, for example, to accomplish this with a single control system, and by the help of a tele-control system, which is built into the television receiver, to operate the channel selection and drive mechanism control, the control for an electronic switch clock and programming of the switch commands of the picture tape recorder as well as the control of the function of the receiving and displaying unit of the receiver. In this way it is possible to use the tele-control of a television receiver additionally for the tele-control of the picture tape recorder without substantial higher expenses.

Power supply is based on TDA4601d (SIEMENS)

TDA4601 Operation. * The TDA4601 device is a single in line, 9 pin chip. Its predecessor was the TDA4600 device, the TDA4601 however has improved switching, better protection and cooler running. The (SIEMENS) TDA4601 power supply is a fairly standard parallel chopper switch mode type, which operates on the same basic principle as a line output stage. It is turned on and off by a square wave drive pulse, when switched on energy is stored in the chopper transformer primary winding in the form of a magnetic flux; when the chopper is turned off the magnetic flux collapses, causing a large back emf to be produced. At the secondary side of the chopper transformer this is rectified and smoothed for H.T. supply purposes. The advantage of this type of supply is that the high chopping frequency (20 to 70 KHz according to load) allows the use of relatively small H.T. smoothing capacitors making smoothing easier. Also should the chopper device go short circuit there is no H.T. output. In order to start up the TDA4601 I.C. an initial supply of 9v is required at pin 9, this voltage is sourced via R818 and D805 from the AC side of the bridge rectifier D801, also pin 5 requires a +Ve bias for the internal logic block. (On some sets pin 5 is used for standby switching). Once the power supply is up and running, the voltage on pin 9 is increased to 16v and maintained at this level by D807 and C820 acting as a half wave rectifier and smoothing circuit. PIN DESCRIPTIONS Pin 1 This is a 4v reference produced within the I.C. Pin 2 This pin detects the exact point at which energy stored in the chopper transformer collapses to zero via R824 and R825, and allows Q1 to deliver drive volts to the chopper transistor. It also opens the switch at pin 4 allowing the external capacitor C813 to charge from its external feed resistor R810. Pin 3 H.T. control/feedback via photo coupler D830. The voltage at this pin controls the on time of the chopper transistor and hence the output voltage. Normally it runs at Approximately 2v and regulates H.T. by sensing a proportion of the +4v reference at pin 1, offset by conduction of the photo coupler D830 which acts like a variable resistor. An increase in the conduction of transistor D830 and therefor a reduction of its resistance will cause a corresponding reduction of the positive voltage at Pin 3. A decrease in this voltage will result in a shorter on time for the chopper transistor and therefor a lowering of the output voltage and vice versa, oscillation frequency also varies according to load, the higher the load the lower the frequency etc. should the voltage at pin 3 exceed 2.3v an internal flip flop is triggered causing the chopper drive mark space ratio to extend to 244 (off time) to 1 (on time), the chip is now in over volts trip condition. Pin 4 At this pin a sawtooth waveform is generated which simulates chopper current, it is produced by a time constant network R810 and C813. C813 charges when the chopper is on and is discharged when the chopper is off, by an internal switch strapping pin 4 to the internal +2v reference, see Fig 2. The amplitude of the ramp is proportional to chopper drive. In an overload condition it reaches 4v amplitude at which point chopper drive is reduced to a mark-space ratio of 13 to 1, the chip is then in over current trip. The I.C. can easily withstand a short circuit on the H.T. rail and in such a case the power supply simply squegs quietly. Pin 4 is protected by internal protection components which limit the maximum voltage at this pin to 6.5v. Should a fault occur in either of the time constant components, then the chopper transistor will probably be destroyed. Pin 5 This pin can be used for remote control on/off switching of the power supply, it is normally held at about +7v and will cause the chip to enter standby mode if it falls below 2v. Pin 6 Ground. Pin 7 Chopper switch off pin. This pin clamps the chopper drive voltage to 1.6v in order to switch off the chopper. Pin 8 Chopper base current output drive pin. Pin 9 L.T. pin, approximately 9v under start-up conditions and 16v during normal running, Current consumption of the I.C. is typically 135mA. The voltage at this pin must reach 6.7v in order for the chip to start-up.

BU208(A)

Silicon NPN
npn transistors,pnp transistors,transistors
Category: NPN Transistor, Transistor
MHz: <1 MHz
Amps: 5A
Volts: 1500V
HIGH VOLTAGE CAPABILITY
JEDEC TO-3 METAL CASE.

DESCRIPTION
The BU208A, BU508A and BU508AFI are
manufactured using Multiepitaxial Mesa
technology for cost-effective high performance
and use a Hollow Emitter structure to enhance
switching speeds.

APPLICATIONS:
* HORIZONTAL DEFLECTION FOR COLOUR TV With 110° or even 90° degree of deflection angle.

ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
VCES Collector-Emit ter Voltage (VBE = 0) 1500 V
VCEO Collector-Emit ter Voltage (IB = 0) 700 V
VEBO Emitter-Base Voltage (IC = 0) 10 V
IC Collector Current 8 A
ICM Collector Peak Current (tp < 5 ms) 15 A
TO - 3 TO - 218 ISOWATT218
Ptot Total Dissipation at Tc = 25 oC 150 125 50 W
Tstg Storage Temperature -65 to 175 -65 to 150 -65 to 150 oC
Tj Max. Operating Junction Temperature 175 150 150 °C

The invention relates to a blocking oscillator type switching power supply for supplying power to electrical equipment, wherein the primary winding of a transformer, in series with the emitter-collector path of a first bipolar transistor, is connected to a d-c voltage obtained by rectification of a line a-c voltage fed-in via two external supply terminals, and a secondary winding of the transformer is provided for supplying power to the electrical equipment, wherein, furthermore, the first bipolar transistor has a base controlled by the output of a control circuit which is acted upon in turn by the rectified a-c line voltage as actual value and by a set-point transmitter, and wherein a starting circuit for further control of the base of the first bipolar transistor is provided.
Such a blocking oscillator switching power supply is described in the German periodical, "Funkschau" (1975) No. 5, pages 40 to 44. It is well known that the purpose of such a circuit is to supply electronic equipment, for example, a television set, with stabilized and controlled supply voltages. Essential for such switching power supply is a power switching transistor i.e. a bipolar transistor with high switching speed and high reverse voltage. This transistor therefore constitutes an important component of the control element of the control circuit. Furthermore, a high operating frequency and a transformer intended for a high operating frequency are provided, because generally, a thorough separation of the equipment to be supplied from the supply naturally is desired. Such switching power supplies may be constructed either for synchronized or externally controlled operation or for non-synchronized or free-running operation. A blocking converter is understood to be a switching power supply in which power is delivered to the equipment to be supplied only if the switching transistor establishing the connection between the primary coil of the transformer and the rectified a-c voltage is cut off. The power delivered by the line rectifier to the primary coil of the transformer while the switching transistor is open, is interim-stored in the transformer and then delivered to the consumer on the secondary side of the transformer with the switching transistor cut off.
In the blocking converter described in the aforementioned reference in the literature, "Funkschau" (1975), No. 5, Pages 40 to 44, the power switching transistor is connected in the manner defined in the introduction to this application. In addition, a so-called starting circuit is provided. Because several diodes are generally provided in the overall circuit of a blocking oscillator according to the definition provided in the introduction hereto, it is necessary, in order not to damage these diodes, that due to the collector peak current in the case of a short circuit, no excessive stress of these diodes and possibly existing further sensitive circuit parts can occur.
Considering the operation of a blocking oscillator, this means that, in the event of a short circuit, the number of collector current pulses per unit time must be reduced. For this purpose, a control and regulating circuit is provided. Simultaneously, a starting circuit must bring the blocking converter back to normal operation when the equipment is switched on, and after disturbances, for example, in the event of a short circuit. The starting circuit shown in the literature reference "Funkschau" on Page 42 thereof, differs to some extent already from the conventional d-c starting circuits. It is commonly known for all heretofore known blocking oscillator circuits, however, that a thyristor or an equivalent circuit replacing the thyristor is essential for the operation of the control circuit.
It is accordingly an object of the invention to provide another starting circuit. It is a further object of the invention to provide a possible circuit for the control circuit which is particularly well suited for this purpose. It is yet another object of the invention to provide such a power supply which is assured of operation over the entire range of line voltages from 90 to 270 V a-c, while the secondary voltages and secondary load variations between no-load and short circuit are largely constant.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a blocking oscillator-type switching power supply for supplying power to electrical equipment wherein a primary winding of a transformer, in series with an emitter-collector path of a first bipolar transistor, is connected to a d-c voltage obtained by rectification of a line a-c voltage fed-in via two external supply terminals, a secondary winding of the transformer being connectible to the electrical equipment for supplying power thereto, the first bipolar transistor having a base controlled by the output of a control circuit acted upon, in turn, by the rectified a-c line voltage as actual value and by a set-point transmitter, and including a starting circuit for further control of the base of the first bipolar transistor, including a first diode in the starting circuit having an anode directly connected to one of the supply terminals supplied by the a-c line voltage and a cathode connected via a resistor to an input serving to supply power to the control circuit, the input being directly connected to a cathode of a second diode, the second diode having an anode connected to one terminal of another secondary winding of the transformer, the other secondary winding having another terminal connected to the emitter of the first bipolar transmitter.
In accordance with another feature of the invention, there is provided a second bipolar transistor having the same conduction type as that of the first bipolar transistor and connected in the starting circuit with the base thereof connected to a cathode of a semiconductor diode, the semiconductor diode having an anode connected to the emitter of the first bipolar transistor, the second bipolar transistor having a collector connected via a resistor to a cathode of the first diode in the starting circuit, and having an emitter connected to the input serving to supply power to the control circuit and also connected to the cathode of the second diode which is connected to the other secondary winding of the transformer.
In accordance with a further feature of the invention, the base of the second bipolar transistor is connected to a resistor and via the latter to one pole of a first capacitor, the anode of the first diode being connected to the other pole of the first capacitor.
In accordance with an added feature of the invention, the input serving to supply power to the control circuit is connected via a second capacitor to an output of a line rectifier, the output of the line rectifier being directly connected to the emitter of the first bipolar transistor.
In accordance with an additional feature of the invention, the other secondary winding is connected at one end to the emitter of the first bipolar transistor and to a pole of a third capacitor, the third capacitor having another pole connected, on the one hand, via a resistor, to the other end of the other secondary winding and, on the other hand, to a cathode of a third diode, the third diode having an anode connected via a potentiometer to an actual value input of the control circuit and, via a fourth capacitor, to the emitter of the first bipolar transistor.
In accordance with yet another feature of the invention, the control circuit has a control output connected via a fifth capacitor to the base of the first bipolar transistor for conducting to the latter control pulses generated in the control circuit.
In accordance with a concomitant feature of the invention, there is provided a sixth capacitor shunting the emitter-collector path of the first transistor.
Other features which are considered as characteristic for the invention are set forth in the appended claim.
Although the invention is illustrated and described herein as embodied in a blocking oscillator type switching power supply, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.









 GRUNDIG Simplified horizontal /  line deflection circuit.
-----------------------------------------------------------------------------------------------
This GRUNDIG CHASSIS Series was featuring a Simplified BU208A transistor  based horizontal deflection section replacing all Thyristor horizontal timebase based circuits.

A horizontal deflection circuit makes a sawtooth
current flow through a deflection coil. The current
will have equal amounts of positive and negative
current. The horizontal switch transistor conducts
for the right hand side of the picture. The damper
diode conducts for the left side of the picture.
Current only flows through the fly back capacitor
during retrace time.



For time 1 the transistor is turned on. Current
ramps up in the yoke. The beam is moved from the
center of the picture to the right edge. Energy is
stored on the inductance of the yoke.
E=I2L/2


For time 2 the transistor is turned off. Energy
transfers from the yoke to the flyback capacitor. At
the end of time two all the energy from the yoke is
placed on the flyback capacitor. There is zero
current in the yoke and a large voltage on the
capacitor. The beam is quickly moved from the
right edge back to the middle of the picture.









During time 3 the energy on the capacitor flows
back into the yoke. The voltage on the flyback
capacitor decreases while the current in the yoke
builds until there is no voltage on the capacitor. By
the end of time 3 the yoke current is at it's
maximum amount but in the negative direction.
The beam is quickly deflected form the center to the
left edge.






Time 4 represents the left hand half of the picture.
Yoke current is negative and ramping down. The
beam moves from the left to the center of the
picture.












The current that flows when the horizontal switch is
closed is approximately:
Ipk ≅ Vcc T / Ldy
Ipk = collector current
T = 1/2 trace time
Ldy = total inductance (yoke + lin coil + size coil)
note:The lin coil inductance varies with current.
______
Tr ≅ 3.14 √ L C
The current that flows during retrace is produced by
the C and L oscillation. The retrace time is 1/2 the
oscillation frequency of the L and C.
I2L /2 ≅ V2C /2 or I2L = V2C As stated earlier the energy in the yoke moves to the
flyback capacitor during time 2.
V= the amount of the flyback pulse that is above the
supply voltage.


D.C. annualizes is inductors are considered
shores, capacitors are open and generally
semiconductors are removed. The voltage at the
point “B+” is the supply voltage. The collector
voltage of Q1 is also at the supply voltage. The
voltage across C2 is equal to the supply voltage.
When we A.C. annualize this circuit we will find
that the collector of Q1 has a voltage that ranges
from slightly negative to 1000 volts positive. The
average voltage must remain the same as the D.C.
value.
In the A.C. annualizes of the circuit, the
inductance of the yoke (DY) and the inductance of
the flyback transformer are in parallel. The
inductance of T2 is much larger than that if the
DY. This results is a total system inductance of
about 10% to 20% less than that of the DY it’s
self.
The voltage across the Q1 is a half sinusoid pulse during the flyback or retrace period and close to zero at
all other times. It is not possible or safe to observe this point on an oscilloscope without a proper high
frequency high voltage probe. Normally use a 100:1 probe suitable for 2,000V peak. The probe must have
been high frequency calibrated recently.
GENERAL BASIC TRANSISTOR LINE OUTPUT STAGE OPERATION:

The basic essentials of a transistor line output stage are shown in Fig. 1(a). They comprise: a line output transformer which provides the d.c. feed to the line output transistor and serves mainly to generate the high -voltage pulse from which the e.h.t. is derived, and also in practice other supplies for various sections of the receiver; the line output transistor and its parallel efficiency diode which form a bidirectional switch; a tuning capacitor which resonates with the line output transformer primary winding and the scan coils to determine the flyback time; and the scan coils, with a series capacitor which provides a d.c. block and also serves to provide slight integration of the deflection current to compensate for the scan distortion that would otherwise be present due to the use of flat screen, wide deflection angle c.r.t.s. This basic circuit is widely used in small -screen portable receivers with little elaboration - some use a pnp output transistor however, with its collector connected to chassis.

Circuit Variations:
Variations to the basic circuit commonly found include: transposition of the scan coils and the correction capacitor; connection of the line output transformer primary winding and its e.h.t. overwinding in series; connection of the deflection components to a tap on the transformer to obtain correct matching of the components and conditions in the stage; use of a boost diode which operates in identical manner to the arrangement used in valve line output stages, thereby increasing the effective supply to the stage; omission of the efficiency diode where the stage is operated from an h.t. line, the collector -base junction of the line output transistor then providing the efficiency diode action without, in doing so, producing scan distortion; addition of inductors to provide linearity and width adjustment; use of a pair of series -connected line output transistors in some large -screen colour chassis; and in colour sets the addition of line convergence circuitry which is normally connected in series between the line scan coils and chassis. These variations on the basic circuit do not alter the basic mode of operation however.

Resonance
The most important fact to appreciate about the circuit is that when the transistor and diode are cut off during the flyback period - when the beam is being rapidly returned from the right-hand side of the screen to the left-hand side the tuning capacitor together with the scan coils and the primary winding of the line output transformer form a parallel resonant circuit: the equivalent circuit is shown in Fig. 1(b). The line output transformer primary winding and the tuning capacitor as drawn in Fig. 1(a) may look like a series tuned circuit, but from the signal point of view the end of the transformer primary winding connected to the power supply is earthy, giving the equivalent arrangement shown in Fig. 1(b).

The Flyback Period:
Since the operation of the circuit depends mainly upon what happens during the line flyback period, the simplest point at which to break into the scanning cycle is at the end of the forward scan, i.e. with the beam deflected to the right-hand side of the screen, see Fig. 2. At this point the line output transistor is suddenly switched off by the squarewave drive applied to its base. Prior to this action a linearly increasing current has been flowing in the line output transformer primary winding and the scan coils, and as a result magnetic fields have been built up around these components. When the transistor is switched off these fields collapse, maintaining a flow of current which rapidly decays to zero and returns the beam to the centre of the screen. This flow of current charges the tuning capacitor, and the voltage at A rises to a high positive value - of the order of 1- 2k V in large -screen sets, 200V in the case of mains/battery portable sets. The energy in the circuit is now stored in the tuning capacitor which next discharges, reversing the flow of current in the circuit with the result that the beam is rapidly deflected to the left-hand side of the screen - see Fig. 3. When the tuning capacitor has discharged, the voltage at A has fallen to zero and the circuit energy is once more stored in the form of magnetic fields around the inductive components. One half -cycle of oscillation has occurred, and the flyback is complete.

Energy Recovery:
First Part of Forward Scan The circuit then tries to continue the cycle of oscillation, i.e. the magnetic fields again collapse, maintaining a current flow which this time would charge the tuning capacitor negatively (upper plate). When the voltage at A reaches about -0.6V however the efficiency diode becomes forward biased and switches on. This damps the circuit, preventing further oscillation, but the magnetic fields continue to collapse and in doing so produce a linearly decaying current flow which provides the first part of the forward scan, the beam returning towards the centre of the screen - see Fig. 4. The diode shorts out the tuning capacitor but the scan correction capacitor charges during this period, its right-hand plate becoming positive with respect to its left-hand plate, i.e. point A. Completion of Forward Scan When the current falls to zero, the diode will switch off. Shortly before this state of affairs is reached however the transistor is switched on. In practice this is usually about a third of the way through the scan. The squarewave applied to its base drives it rapidly to saturation, clamping the voltage at point A at a small positive value - the collector emitter saturation voltage of the transistor. Current now flows via the transistor and the primary winding of the line output transformer, the scan correction capacitor discharges, and the resultant flow of current in the line scan coils drives the beam to the right-hand side of the screen see Fig. 5.

Efficiency:
The transistor is then cut off again, to give the flyback, and the cycle of events recurs. The efficiency of the circuit is high since there is negligible resistance present. Energy is fed into the circuit in the form of the magnetic fields that build up when the output transistor is switched on. This action connects the line output transformer primary winding across the supply, and as a result a linearly increasing current flows through it. Since the width is
dependent on the supply voltage, this must be stabilised.

Harmonic Tuning:
There is another oscillatory action in the circuit during the flyback period. The considerable leakage inductance between the primary and the e.h.t. windings of the line output transformer, and the appreciable self -capacitance present, form a tuned circuit which is shocked into oscillation by the flyback pulse. Unless this oscillation is controlled, it will continue into and modulate the scan. The technique used to overcome this effect is to tune the leakage inductance and the associated capacitance to an odd harmonic of the line flyback oscillation frequency. By doing this the oscillatory actions present at the beginning of the scan cancel. Either third or fifth harmonic tuning is used. Third harmonic tuning also has the effect of increasing the amplitude of the e.h.t. pulse, and is generally used where a half -wave e.h.t. rectifier is employed. Fifth harmonic tuning results in a flat-topped e.h.t. pulse, giving improved e.h.t. regulation, and is generally used where an e.h.t. tripler is employed to produce the e.h.t. The tuning is mainly built into the line output transformer, though an external variable inductance is commonly found in colour chassis so that the tuning can be adjusted. With a following post I will go into the subject of modern TV line timebases in greater detail with other models and technology shown here at  Obsolete Technology Tellye !

HORIZONTAL SIZE /  E/W AMPLITUDE - CORRECTION CIRCUIT:

There are several different methods of adjusting horizontal size.




SIZE COIL
Add a variable coil to the yoke current path
causes the total inductance to vary with the coils
setting.
The yoke current is related to supply voltage,
trace time and total inductance. This method
has a limited range!
The horizontal section uses a PWM to set the
horizontal size. One DAC sets the horizontal
size and another DAC sets the pincushion and
trap.
The Raster Centering (D.C. centering) is
controlled by a DAC.
On small monitors the retrace time is fixed. On
large monitors or wide frequency range monitors
two different retrace times are available. The flyback time is set by the micro computer by selecting two
different flyback capacitors. At slow frequencies the longer retrace time is selected.
Different S corrector capacitor values are selected by the micro computer. At the highest frequency the
smallest capacitor is selected.



SPLIT DIODE MODULATOR
This horizontal circuit consists of two parts. D1, C1, C2 and DY are the components as described above.
D2, C3, C4 and L1 are a second “dummy” horizontal section that does not cause deflection current. By the
D.C. analyzing this circuit the voltage across C2 + C4 must equal the supply voltage (B+). Deflection
current in the DY is related to the supply voltage minus the voltage across C4. For a maximum horizontal
size the control point must be held at ground. This causes the dummy section to not operate and the DY
section will get full supply voltage. If the control point is at 1/3 supply then the DY section will be
operating at 2/3 supply.
Note: The impedance of (D1,C1,C2 and DY) and (D2,C3,C4 and L1) makes a voltage divider. If the
control point is not connected then there is some natural voltage on C4. Most split diode monitors are built
to pull power from the dummy section through L2 to ground. A single power transistor shunts from the
control point to ground. It is true that power can be supplied from some other supply through L2 to rise the voltage on C4. For maximum range a bi-directional power amplifier can drive the control point.
The most exciting feature if the split diode modulator is that the flyback pulse, as seen by the flyback
transformer, is the same size at all horizontal size settings.


HORIZONTAL SWITCH/DAMPER DIODE
On the right hand side of the screen, the H. switch transistor conducts current through the deflection yoke.
This current comes from the S correction capacitors, which have a charge equal to the effective supply
voltage. The damper diode allows current for the left hand side of the screen to flow back through the
deflection yoke to the S capacitors.
FLYBACK CAPACITOR
The flyback capacitor connects the hot side of the yoke to ground. This component determines the size and
length of the flyback pulse. ‘Tuning the flyback capacitor’ is done to match the timing of the flyback pulse
to the video blanking time of the video signal. The peak flyback voltage on the horizontal switch must be
set to less that 80% if the Vces specification. The two conditions of time and voltage can be set by three
variables (supply voltage, retrace capacitor and yoke inductance) .
S CAPACITOR
The S capacitors corrects outside versus center linearity in the horizontal scan. The voltage on the S cap
has a parabola plus the DC horizontal supply. Reducing the value of S cap increases this parabola thus
reducing the size of the outside characters and increasing the size of the center characters.
S Capacitor value: Too low: picture will be squashed towards edges.
Too high: picture will be stretched towards edges.

By simply putting a capacitor in series with each coil, the sawtooth waveform is
modified into a slightly sine-wave shape. This reduces the scanning speed near the
edges where the yoke is more sensitive. Generally the deflection angle of the electron
beam and the yoke current are closely related. The problem is the deflection angle
verses the distance of movement on the CRT screen does not have a linear effect.

BASE DRIVE CURRENT
The base drive resistor determines the amount of
base drive. If the transistor is over driven the Vsat
looks very good, but the current fall time is poor.
If the base current is too small the current fall time is very fast. The problem is that the transistor will have many volts across C-E when closed.
The best condition is found by placing the transistor in the heaviest load condition. Adjust the base resistor for the least power consumption then increase the base drive a small amount. This will slightly over drive the base.












LIST OF COMMON FAULTS / THROUBLESHOOTING FOR GRUNDIG CHASSIS CUC220:


Grundig CUC220 Dead - intermittent. R646 ( 270k ) on PSU.
Grundig CUC220 Display - intermittent incorrect channel disp IC663 ( 5v reg )
Grundig CUC220 Excess col & brightness when heated OK when Txt pcb dis'd - left it this way
Grundig CUC220 Frame collapse. R2779 ( 18k ) o/c remove to check.
Grundig CUC220 Frame distortion. IC TDA1770 if used , D2761 ( SKE4G1/04 ) , R2761 ( 6.8ohm , .75W )
Grundig CUC220 Goes straight off at sw on odd characters in display - HT = 180v (109v) HT pot int
Grundig CUC220 Horizontal shaking. Tuner/IF dry joints , check the electrolytics with freezer
Grundig CUC220 INT START UP C631 100uF 40v , C633 220uF , C647 1uF , C642 100uF + R646 270k
Grundig CUC220 int start up TDA4600
Grundig CUC220 Interference at sides. IC TDA2595 sync/line osc IC.
Grundig CUC220 Lack of frame at bottom when cold. C2768 ( 100uf ) on deflection PCB.
Grundig CUC220 No pic at switch on - looks like its off tune C2221 ( 1uf 63v ) in tuner/if unit.
Grundig CUC220 No vision with raster and sound. T2533 , Adj control SB , R2536 , C2536 , D2536 , D2532
Grundig CUC220 Pulling/Rolling C2216/2221 1µ 63v in IF can by TDA5500 chip
Grundig CUC220 Shutdown - intermittent switching off. Dry R646 ( 270k ) , TDA4600 , replace HT pot R647 ( 2.5k )
Grundig CUC220 Standby - intermittent going into standby. Change R647 to ceramic.
Grundig CUC220 Standby- intermittent going into standby. IC663 ( 5v reg )
Grundig CUC220 Startup - switch on problems & hum. Relay contacts jammed o/c.