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8. RA-4/4A Power Supply Troubleshooting
FIGURE 8-3 - VCC SWITCH
STANDBY
SOURCE
VOLTAGE
FROM D6003/K
R6043
R6042
D6035
RD12ESB2
C6037
R6040
Q6012
P
FROM
D6015/K
VCC
SOURCE
R6018
R6039
Q6013
C6036
D6034
R6019
Q6011
VCC SW P
R6041
Q6001
D6033
TO R6023 VCC
& R6016
SOFT START
TO IC6003 OSC
TO IC6002
DRIVER
TO IC6004 DRIVER
TO RY6001
POWER RELAY
TO D6010
SOFT START
RESET
S
LINK
ST 5V
A BOARD
IC1008
MAIN CPU
CX98585X-XXX
IRMCN
KEY 0
0 RELAY
CN505
R6112
CN6101
D6111
R6121 D6112
R6125
R6126
N
Q6104
IC6011
FROM IC6104/2
S5V
FROM Q6103/C
LATCH
G BOARD
64
14
23
40
41
44
56
4
3
2
1
3
3
8.3TVP14
7/17/02
FROM
Q6005
D6031
R6020
VCC Switching
This circuit is responsible for supplying power to the main relay along with the main oscillator and power switching
circuits. It is quite different from conventional designs used in previous models. In Figure 8-3, it is shown that
rather than using the relay high command from the CPU to directly control a relay drive transistor, an optical-
isolator, IC6011, is turned on by Q6104. A ground return will be provided to Q6001-E, turning on Q6011. This
transistor will provide power to the above circuits, which includes direct power to the main relay, which is tied to
ground. Notice the latch circuit consisting of Q6012 and Q6013. This is not the same latch circuit that would put
the unit into conventional protect mode. It is only activated if the unregulated B+ for the standby supply rises
above an acceptable level, which is monitored by the divider network R6042 and R6043 along with D6035. A
variac with the capability to output 150AC was unable to trip this circuit so it is assumed that it is there to prevent
accidental application of 220VAC to the unit.
Main Power Supply Troubleshooting
The main supply consists of five major components. IC6003 is an oscillator circuit and will provide square wave
out of pins 9 and 10. These 50/50 duty cycle signals will be 180 degrees out-of-phase and will be applied to
IC6002 and IC6004. Two independent switching circuits consisting of FET drivers and transformers will supply
the television with the necessary voltages for operation.
In Figure 8-4, the oscillator section is shown. Like the standby oscillator, IC6001, this IC will oscillate without the
need for feedback. As long as unregulated B+ is present at pin 12 and the IC is not being told to stop, it will run
and output the necessary square waves at pins 9 and 10. The oscillator will stop running if pin 2 is pulled low by
the inrush current relay monitoring circuit.