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Thursday, 9 October 2014

SERVICING COLOUR TVs THROUGH REMOTE CONTROL HANDSET



Initially the Remote Control Handset was used as a remote operating unit for the TV set, i.e. to control various functions of the tv set from a distance. But currently the remote control unit is also used as a service instrument. Using the remote control unit one can adjust various service parameters of the TV set.
Serving a TV set or adjusting various parameters of the TV set using the remote control can be done only if the manufacturer has provided remote control service facility in the TV set.
To activate the remote service option one need to enter special remote service code, using various combination of keys on the remote control handset and the TV set front panel. This is done to stop the general TV users from fidding with these controls, which may make the TV set inoperable.

What is Remote Service Process ?

In old colour TV sets various adjustments were done with presets, which the TV technician adjusted to change various parameters such as sub-brightness, horizontal/vertical position, height, vertical linerarity, vertical centering etc.
In new generation TV sets all these settings are done in the remote service mode using the remote control handset.

Why the remote control service was introduced?

Initially when the preset controls were provided on the TV set circuit board, as all the controls looked the same, TV technicians, by mistake, many a times adjusted wrong preset. This mistune the TV set and made proper adjustment very difficule.Also, many a times user himself open the TV Set’s back cover and try to change/set these preset, which again misalign the TV set and made proper alignment of various settings of the TV set very difficult.
All this has led to the introduction of the remote control service facillit in current generation of TV sets. These TV sets do not contain any presets and all the setting, which was previously done using the presets in are now done using the remote control in these TV sets.

How to recognize if a TV has remote control service facility?

One very easy method to find out if the TV set has remote service facility is to opern the TV set and check if the TV has presets for various adjustments.
If the TV set has no service adjustments presets ( or very minimum presets ) then the TV will have remote control service facility. Also if the TV has Bus Chassis based board, then the TV must be having remote service facility.
One can also check the remote control handset to find out if the TV has remote control service facility. For this look for some special keys on the remote control handset.
Also, open the remote control front cover and look for any additional keys on the remote PCB, which are not provided on the front cover.
These keys most probably are used to activate the remote service mode. Short these keys and check if the TV set goes into special service mode.

What is BUS CHASSIS  or I2C BUS ?

In a Bus chassis or i2c Bus based television, the exchange of signals between of signals between the microprocessor and various sections of the television receiver does not require different signal lines.
Instead the microprocessor communicates with different sections of the television receiver using to lines, knows as Data line (SDA ) and Clock line (SCL) . These lines provide path for two way communication between the microprocessor and different sections of the television receiver.
In I2C bus system, device which generates the data and starts the data transfer process is known as master, the clock signals is also generated by the master device and the device which receives the data is known as slave device.
Given figure shown the concept of I2c bus system. All modern television receivers use the i2c bus to transfer control signal to its various sections.

Section which can be adjusted in Remote Service mode

As the remote control service is a substitute for the presets on the old TV sets, one van do all those adjustments which was possible with the presets using the remote service facility.
For example, various controls of the horizontal and vertical section van be done in the remote control service mode. Sub –brightness, sub-contrast, AGC, etc. All these setting can be done in the remote control service mode.

Advantage/ Disadvantage of Remote Service

One very big advantage of remote service facility is, it makes it very easy for the serve engineers to do different adjustments.
Also, it makes it difficult for the common man to change the preset values and disturb setting of the TV set. Another advantage remote service mode is, one need not open the TV set for doing various adjustments.
One disadvantage of this method is, it makes it difficult for the common technician to make varuous adjustments to the TV set, as the method to enter into the service mode of various TV sets are not commonly available.

How to enter into Remote Service Mode ?

If the remote control handset had hidden remote service key then by shorting these keys ( if front of the TV set ) one can get the remote service menu on the TV set. If the remote has no servie key then by pressing various combination of the remote key and front panel key one can get the remote service mode.
This combination if keys that one need to press to enter into service mode is known as remote service code.

Remote Service Mode Precautions

After entering into service mode, one should not change any value unnecessarily. Also, note down the default value before making any change so that one can return the TV set to its original condition, if some setting goes wrong.



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