Specifications

CA1 Course Notes
Sharp Electronics (UK) Limited
CE Technical Support Group Page 47
Introduction to the CA1 Chassis
As the CA10 chassis is designed for use as a NICAM and fast text unit, it is not suitable to be used in the
small screen models that only feature basic functions. For this reason, the Sharp development engineers
at the Spanish factory, located in Barcelona, have designed a small screen chassis, this is designated the
CA1.
Use is made of a relatively standard chip set as outlined below :-
IC201 ( TDA8840 ) - this is the main Y/C processing and time base generator IC that also
contains all of the IF ( audio and video ) and audio analogue processing circuit ( except for audio
output ).
IC1001 - this is the main processor unit that controls the functionality of the receiver. It is a
masked device and therefore must be replaced with the correct type from the Sharp Spare Parts
Centre if it fails. Note that within the teletext versions of the CA1 chassis this IC will contain the
teletext processor.
IC1002 - is the non volatile memory that contains all the pre-set information for this receiver. It
is important that the correct part number is used when obtaining a replacement device.
Although similar in many respects to the CA10, there are a number of important differences as indicated
in the list below :-
1. The chopper power supply circuit is virtually the same as the CA10, but the component
references are different. The voltage regulation circuit on the isolated side of the power
supply is simpler and is covered in the CA1 Power Supply section.
2. No class D amplifiers are used, instead discrete component linear amplifiers have been
used for both the vertical and sound output stages and are described in detail later in
these notes. Note that the vertical output stage has been used in many previous Sharp
small screen models.
3. Data communication is simpler, as only one I C bus is used and there is no external
2
EEPROM as the microprocessor has this fitted internally ( masked processor ). To
reduce the component count even further on the teletext models, the teletext processing
action is also contained within the microprocessor.
4. As the power supply is kept running in this chassis, it is necessary to switch some of the
secondary supplies, this is covered in the CA1 Power On Control section
5. A more sophisticated protection circuit is connected to the main processor. This is
discussed in the CA1 Protection section.
6.` The line driver circuit is different, and is described in the CA1 Line Stage section.
Note that the CA1 chassis section of these notes are based upon the 37DM23H service manual ( part
number SELH37DM23H// ). This service manual is available from Teega Agencies, telephone number
01282 419917.