Chapter 1 - Brief Circuit Descriptions; Introduction; Overall Block Diagram; Cf1 Board - Sony KDL70XBR7 Training Manual

Introduction

The KDL70XBR7 utilizes the EZ-1 chassis as its platform. This stand-
alone training manual is written to cover the circuits in this television that
are unique to this 70-inch panel design. Video and audio processing is
virtually the same as the other models incorporating the EZ-1 chassis.
Features are also the same and this information is covered in the CTV-50
training manual. The focus of this manual is to cover the power supply
and backlight inverter circuits that are unique to this model and to provide
troubleshooting techniques for repair by the authorized service network.

Overall Block Diagram

Figure 1-1 illustrates an overall block diagram of the KDL70XBR7. As
mentioned previously, audio and video switching and processing is
performed by the circuits on the AU and FB boards. Detailed descriptions
of these circuits can be found in the CTV-50 training manual.

CF1 Board

Unique to this model, the CF1 board contains circuits to capture the video
frames exiting the FBU board and convert them from 60HZ to 120HZ
refresh rate. Other models in the EZ-1 chassis family perform this task on
the TCON board. The CF1 board is considered part of the LCD panel and
is not available as a replacement item.

Power Supply

Due to the high current demand of this model, 3 power supply circuits
are utilized. AC input is applied to the F2 board. This board contains line
filtering and transient protection along with main AC fuses.

G8 Board

The filtered AC voltage is applied to the G8 board. The primary function of
this board is to provide operating B+ voltages for most of the circuits in the
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Chapter 1 – Brief Circuit Descriptions
television. It also provides the un-switched AC to the pair of G9 Boards
along with a DC voltage known as PRI_VCC. This voltage is what turns on
the G9 boards so they will not function if there is a failure of the G8 board.
This description will be covered in more detail later in this manual.

G9 Boards

The G9 power supply boards are identical and are dedicated to supplying
24VDC to the left and right inverter boards. AC power is supplied from the
G8 board along with a DC voltage (PRI_VCC) to turn them on.

Inverters

High voltage to power the fluorescent backlights is generated by the left
and right inverter boards. Due to the extreme width of the LCD screen,
the fluorescent lamps are not arranged in a horizontal array as found in
most LCD televisions. The KDL70XBR7 has an array of lamps mounted
vertically.
High voltage from the inverters is sent to 4 balancer boards. The balancers
distribute the high voltage to the fluorescent lamps along with current
balancing of the lamps and monitoring for any open lamp condition. Each
balancer distributes high voltage to 16 lamps for a total of 64 fluorescent
backlights.

Cooling Fans

The heat generated by the CCFL backlights and the high frame-rate video
processing requires the use of cooling fans. The television used in the
development of this manual contained 2 cooling fans. Final production
units may only contain a single fan. The drive circuits for the fan(s) are
located on the AU board. The fan(s) contain internal rotation detection
circuits and will send a rotation error high to the AU board if the fan fails to
rotate or if the detection circuit fails. The unit will shut down with a 9-blink
error code if this happens.
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