Service manual

PV152 3-5 PROJO
CIRCUIT DESCRIPTION
SPOT PROTECT or SPOT KILLER:
As mentioned earlier, when the deflection power supply
goes into shutdown for whatever reason, a low potential
will be applied at the cathode of DN14, forward biasing it
and causing current flow through RN07. Once again, this
increase of current flow through RN07 will bias on QN04
and the events described previously will occur.
SWEEP LOSS DETECTION:
The key component in the Sweep Loss Detection circuit is
QN04. This transistor is normally biased off. When the base
becomes more negative, it will be turned on, causing the
Standby 11V to be applied to two different circuits, the
Spot circuit and the High Voltage Drive circuit.
VERTICAL / HORIZONTAL BLANKIN:
Loss of Vertical Blanking:
When the 24Vpp positive vertical blanking pulse is miss-
ing from the base of QN01, it will be turned off, which will
cause the collector to go high. This in turn will cause QN02
to turn on, creating an increase of current flow from emit-
ter to collector and up through RN07, (which is located
across the emitter base junction of QN04), to the 11V
standby supply. This increase of current flow through RN07
will bias on QN04 and the events described previously will
occur.
Loss of Horizontal Blanking:
When the 11.6Vpp positive horizontal blanking pulse is
missing from the base of QN05, it will be turned off, which
will cause the collector to go high. This in turn will cause
QN03 to turn on, creating an increase of current flow from
emitter to collector, through RN06, and up through RN07.
Again, this increase of current flow through RN07 will bias
on QN04 and the events described previously will occur.
CONCERNING QN04:
There are several factors that can affect the operation of
QN04; namely loss of vertical or horizontal blanking and
spot killer or spot protect from a shutdown in the deflec-
tion power supply.
MICRO PROCESSOR DATA COMMUNICATION
The Microprocessor must keep in communication with the
Chassis to maintain control over the individual circuits.
Some of the circuits must return information as well so the
Microprocessor will know how to respond to different re-
quest. The Microprocessor uses a combination of I 2 C Bus
communication and the Standard Data, Clock and Load lines
for control. The I 2 C communication scheme only requires
2 lines for control. These lines are called SDA and SCL. Sys-
tem Data and System Clock respectively. The Microproces-
sor also requires the use of what are called Fan Out ICs or
DACs, (Digital to Analog Converters). This allows the Mi-
croprocessor to use only two lines to control many differ-
ent circuits. Also, due to the fact that this Microprocessor
operates at the new 3.3Vdc voltage, it requires a Level
Shift IC to bring up the DC level of the control lines to
make it compatible with the connected ICs.
ON THE SIGNAL PWB:
Main Tuner U201:
The Microprocessor controls the Main Tuner by Clock, Data
and Enable lines. Clock, Data and Enable lines for the Main
Tuner are output from the Microprocessor at pins (20 Clock,
21 Data and 44 FEENABLE1) respectively. Pin (44) FEENABLE1
goes directly to the Main Tuner at pin (6), where as the
Clock and Data lines must be routed through the Level
Shift IC I014 to be brought up to 5V. Clock and Data from
the Microprocessor arrive at I014 (Level Shift) at pins (2
and 3) and are output at pins (18 and 17). They arrive at
the Main Tuner at pins (4 and 5).
PIP Tuner U202:
The only difference for the PinP tuner control lines is re-
lated to the PinP Enable line. This is output from the Mi-
croprocessor pin (43 FEENABLE2) to the PinP Tuner at pin
(17). Clock and Data are the same as for the Main Tuner.
EEPROM I002:
The EEPROM is ROM for many different functions of the
Microprocessor. Channel Scan or Memory List, Customer set
ups for Video, Audio, Surround etc… are memorized as
well. Also, some of the Microprocessors internal sub rou-
tines have variables that are stored in the EEPROM, such as
the window for Closed Caption detection. Data and Clock
lines are SDA1 from pin (2) of the Microprocessor to pin
(5) of the EEPROM and SCL2 from pin (3) of the Micropro-
cessor to pin (6) of the EEPROM. Data travels in both di-
rections on the Data line.
Flex Converter U205:
The projection television is capable of two different hori-
zontal frequencies. 31.75Khz for everything except HD and
33.75Khz for HD. (High Definition). The Flex Converter is
responsible for receiving any video input and converting
it to the related output. This output is controlled by sync
and by the customer’s menu and how it is set up. The set
up can be 4X3 or 16X9, sometimes called letterbox. The
Flex Converter can take any NTSC, S-In, Component in NTSC,
Progressive, Interlaced, 480I, 720P, 1080I signal. Control
for the Flex Converter is Clock, Data and Enable lines. Clock,
Data and Enable lines for the Flex Converter are output
from the Microprocessor at pins (20 Clock, 21 Data and 46
FCENABLE). FCENABLE Clock and Data lines must be routed
through the Level Shift IC I014 to be brought up to 5V.
They arrive at I014 at pins (2 Clock, 3 Data and 4 FCENABLE)
and are output at pins (18, 17 and 16) respectively.