29
Power ON Block
Power Supplies
There are four power supplies in the XBR400 TV:
KV32XBR400 Power Supplies
Name
Board
Start
Purpose
Standby
A
Plug in
5V for Main uCom
7V & 15V for power relay
Primary
A
Power ON
Unreg 11V, 7V, 5V become
regulated 9V, 5V, 3.3V.
Secondary
D
Primary Pre
15V, Main
Relay
+200V for HV stage,
+135V for H. Output, +15V,
+24V for Audio stage
HV Converter
(not shown)
D
Horiz Output
AFC-PLS
31.5kV HV for CRT, Focus
voltage.
Except for the Standby power supply, the Primary, Secondary and HV
Converter supplies are similar. The last three supplies use the same IC in
a similar configuration. How they are turned on and the voltages they
deliver is what makes them different.
Each power supply is turned on in the order listed. The first power supply
is operational when the TV is plugged into AC. When the TV is powered
ON, the second and third supplies are turned ON one after the other.
These supplies power the horizontal stages. Finally, the fourth power
supply is turned ON after the horizontal output transformer develops scan,
filament voltage and AFC pulses. The last power supply is not shown on
this diagram, but knowing when the HV is powered on is important for
troubleshooting.
Standby Power Supply
When the TV is plugged in, the standby power supply outputs three volt-
ages: +15V, +7V, and +5V. A small transformer develops the +15V and
+7V. The +7V is regulated down to +5V to power the Main uCom IC701.
Primary & Secondary Power Supplies
Before power ON can occur, the front panel master ON/OFF button (S01
on the HA board) must be pressed in. This latching switch behind the
button supplies the AC relay (RY6501) with standby 7V. Pressing the
switch again would unlatch the switch and the set would shut OFF.
Power ON can be activated from the remote control or when the front
panel button is latched in. The second half of front panel switch S01 (not
shown) grounds out the power ON input to Main uCom IC701. IC701
powers ON the TV by turning on relay driver Q6527. Q6527 grounds one
end of relay RY6501 and momentarily turns on Q710 via C724. Q710
supplies a 15V to AC relay RY6501 because a relay needs more
voltage to close the contacts than to hold them closed.
Primary Power Supply
This power supply only needs 340Vdc from the bridge rectifier D6530 to
start up and run. Three voltages with the prefix “set” are used on the A
and plug in B and BC boards. The most important voltage is the Pri Pre
15V output that starts up the Secondary power supply on the D board.
Secondary Power Supply
The Secondary Power Supply needs three items to operate:
Three Items needed to run the Secondary Power Supply
Item
From
Purpose
340Vdc (B+)
Bridge Rectifier D6530
Powers the Driver/Output
Pri Pre 15V
voltage
Primary Power Supply
secondary
Starts the oscillator when
more than 15.6Vdc.
Main Relay
(normally HIGH)
Main uCom IC701
Enables IC6501 when
HIGH
This secondary power supply produces the remainder of the low voltages
to power the TV. The +200V feeds the HV Converter power supply. The
+135V powers the Horizontal stages. The +15V makes Main 12, Main 9
and Main 5V used throughout the D board. The +24V feeds the audio
output stage.
Summary of Contents for KV-32XBR400
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