GB2256334A - Colour television set using monochrome tuner and signal processing i.c. - Google Patents

Abstract

A colour television set utilises in place of expensive colour signal processing circuitry, a monomax (RTM) integrated circuit for converting an intermediate frequency signal derived from a colour television signal to a monochrome video signal and a monochrome tuning circuit. The monomax (RTM) IC is so arranged as to provide at the sound intermediate frequency (SIF) pin a composite colour video signal. This arrangement gives good picture quality but enables the receiver to be manufactured cheaply since the in-built alignment (video IF/sound IF) of the monomax (RTM) IC does away with the need for further alignment. <IMAGE>

Description

COLOUR TELEVISION SET Field of the Invention The field of art to which this invention pertains is the alignment system in a colour television set and more particularly the use of black and white electric chip tuner and black and white

monomaxLSUD-system 1.X. in colour television set, wnicn nas provluea a VIF/SIF alignment free intermediate frequency (I.F.) section.

Prior Art The colour television sets available in the market required video and sound intermediate frequency alignment during the assembly i.e. sophisticated alignment equipment and adjustment in picture and sound markers is done manually at the production platform which caused loss of time and cost of production.

Further, special jigs and fixtures are also required for the alignment procedure. Specially the colour T.V. tuner pack is the most expensive part after CRT in present colour television sets.

Summary of this Invention It is, accordingly, a broad objective of the invention to provide a low cost colour television set. The colour television, tuner pack is the most expensive part after CPT in present colour TV sets. This tuner pack is the most expensive part and has been replaced by a low cost black and white mini-tuner which is normally suitable for a very small screen size black and white television sets and cannot be used in colour because of low gain, no AFT feed back option and positive AGC. In this invention the same low cost black and white mini tuner is being used with some modification in the IF section of circuitry. This newly modified/invented IF section gives equally good picture quality using a mini black and white tuner as compared to other colour TV sets with special colour television tuner.

The other advantage of this invented set is that no VIF (video IF) SIF (sound IF) adjustment is required in this design i.e., all variable coil products and transformers have have been deleted and tremendous cost of production has been saved in terms of alignment equipment assembly time and number of components. This feature has been achieved by re-designing a black and white monomax

I.C. circuit to give a composite video signal for colour T.V. The

monomaxLI.C. has been made for black and white TV which converts an IF signal to a monochrome video signal (no colour information).

This I.C. is not capable of producing a chroma signal as per its design. Now in our application, the external circuitry of the same IC has been so designed to generate a composite colour video signal of 2.8 V.P.P. from pin no. 28 of the I.C. which normally generates the sound I.F. signal. So in our application the colour signal has been drawn from sound I.F. output of the black and white monomax I.C. after suitable amplification using very few biasing components.

(The amplification means serves to get the peak to peak value of composite video signal up to 208 volts p.p.).

The black and white monomaxLsub-system I.C. is used with a black and white mini chip tuner in the colour television set for the first time. The black and white mini chip tuner and the black and

white monomaSsub-system I.C. are connected together without any intermediate frequency coils or transformers hence they occupy very small space and have stability in their quality because of manual adjustment, are also more economic, light in weight and require no alignment in the production platform.

Description of the Invention In this invention, the composite video output is drawn from the sound using IF output 5.5 MHz trape and to get the required peak to peak level of composite video signals the biasing of pin 7 and 8 has been changed and an additional resistor is added across these two points to give smooth composite video output. Due to very

precise built in alignment of the monomaxLI.C. no AFT switch is required.

A mini black and white electronic chip tuner is used to minimise the cost of colour television tuner. The use of this tuner for colour television is possible only due to the use of black and

white monomaxLI.C. to give composite video signal.

This invention has also minimised the components and extra shielding in the video intermediate frequency (VIF) and sound intermediate frequency (SIF) sections of colour television and to improve the picture quality due to very precise built in alignment in the I.C. It has simplified the production process and after sale service.

DescriPtion of the Invention with Reference to the AcconipanvinQ Drawings As shown in the accompanying drawings the composite video output is drawn from sound IF output using 5.5 MHz trape to get the required Peak to peak level of composite video signal, the biasing

of pin 7 and 8 of I.C. 001 i.e. black and white monomaxLI.C. has been changed i.e. the value of the outer biasing resistor has been changed and additional resistors are added to give smooth composite video output.

Due to the very precise built in alignment of the black and

white monomaxLI.C. i.e. I.C. No. 001 no AFT switch is required.

Similarly a mini black and white electronic chip tuner is connected with the help of intermediate frequency amplifier Q-101

and filter saw to black and white monomax 5 C which in turn provide us an allignment free reception. The use of this tuner for colour television set is possible only due to modified circuit of black and

white monomaxL1.C. i.e. UUl.

This invention has also minimised the components and extra shielding in VIF and SIF section of colour television and to improve the picture quality due to the very precise built in alignment in the I.C. i.e. process and after sale service.

Thus, the invention provides the following advantages: i) The electronic chip tuner used in this invention is a small component which is light in weight and occupies less space in comparison to the old colour tuner pack, is I.F. alignment free, and the set is cheap, has more productivity which in turn has minimised the cost of whole television set. The cost of this TV set is 25% less as compared to any other standard colour television set.

ii) The production line is very simple and cheap as VIF/SIF alignment equipment i.e. sweep marker generator and oscilloscopes are not required and as such the production period of this set is 10% less than any available colour TV.

iii) The repair and maintenance of the set is very easy because of very simply circuitry.

Claims (4)

1. Video intermediate frequency alignment free colour television using the black and white mini chip electronic tuner and

black and white monomaxlsub-system I.C.

2. A mini electronic chip tuner as claimed in claim No. 1, used as a single tuner for UHF and VHF reception.

3. A colour television receiver including a monomaxtintegrated circuit for converting an intermediate frequency signal derived from a colour television signal to a monochrome video signal and a

monocnrome tuning circuit, the monomaxLintegrated circuit being so arranged that the integrated circuit provides a composite colour video signal at the integrated circuit pin conventionally used for the sound intermediate frequency (SIF) signal.

4. A colour television receiver substantially as hereinbefore described with reference to the drawings.