Specifications

CA10 Course Notes
Sharp Electronics (UK) Limited
CE Technical Support Group Page 45
Practical Fault Finding
I C bus line disconnection
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It is possible to isolate the various devices controlled by the I C line by removing the feed resistors. A
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different symptom will be apparent depending upon which device is isolated as described below.
Tuner
If the tuner is isolated from the I C bus line by removing resistors R201 and R202, all functions will work
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correctly except that there will be no picture, i.e. there will be no output from the tuner and a snowy raster
will appear. This will continue until the blue mute operates
IC201 ( IF, Y/C processor and time base generator )
IC201 can be isolated from the I C bus by disconnecting resistors R232 and R233. When the set is turned
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on, the power supply will run, but there will be no raster. The NICAM LED will flash on/off at a 50% duty
cycle once every second.
IC305 ( Sound processor )
When IC305 is isolated from the I C bus by removing R307 and R308, the picture and OSD operation will
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work correctly, but there will be no sound.
SRS module
If the SRS module is disconnected from the communication lines, by pulling out the sub panel, then there
is no sound but the set continues to function normally.
Shorting of SDA to SCL
If the clock and data lines are shorted together, then the line and frame stages do not start up, although
the power supply is active and the NICAM LED flashes on/off at a 50% duty cycle once every second.
Disconnection of IC703
IC703 provides communication to the primary microprocessor and if it is removed from the circuit all circuit
functions will work correctly except that the set can not be brought out of standby with the use of the front
buttons.