LG PLASMA 42PJ350 _ Va & s ADJUSTMENTS AFTER REPLACING THE POWER SUPPLY BOARD
ADJUSTMENTS
It is critical that the DC Voltage adjustments be checked when;
- SMPS, Y-SUS or Z-SUS board is replaced.
- Panel is replaced, Check Va/Vs since the SMPS does not come with new panel
- A Picture issue is encountered
- As a general rule of thumb when ever the back is removed.
ADJUSTMENT ORDER “IMPORTANT” DC VOLTAGE ADJUSTMENTS
POWER SUPPLY: VS, VA (Always
do first)
Y-SUS: Adjust –Vy, VSC
Z-SUS: Adjust Z-Bias (VZB) WAVEFORM ADJUSTMENTS
Y-SUS: Set-Up, Set-Down
The Waveform adjustment is only necessary
- When the Y-SUS board is replaced
- When a “Mal-Discharge” problem is encountered
- When an abnormal picture issues is encountered.
Always refer to the
Voltage Sticker located on the back of the panel, in the upper Left Hand side
for the correct voltage levels for the VA, VS, -VY, VSC, and Z Bias as these
voltages will vary from Panel to Panel even in the same size category. Set-Up
and Ve are just for Label location identification and are not adjusted in this
panel.
SMPS Part Number: EAY60912401 Check
the silk screen label on the top center of the Power Supply board to identify
the correct part number. (It may vary in your specific model number).
Y-SUSTAIN BOARD:
- Vs: Drives the Display Panel’s Horizontal Electrodes. (From Y-SUS to Z-SUS).
- Va: To Y-SUS, fused then to the X-Boards. (Not used by Z-SUS). Primarily responsible for Display Panel Vertical Electrodes.
- M5V: Used to develop Bias Voltages on the Y-SUS then routed to the Control board and then to the Z-SUS Board.
MAIN BOARD:
- STBY 5V Microprocessor Circuits.
- 17V Audio B+ Supply, Tuner B+ Circuits.
- 5V Signal Processing Circuits
- Also AC_Det (if missing, shuts of TV in 10 seconds) and Error_Det (not used)
ADJUSTMENTS
There
are 2 adjustments located on the Power Supply Board VA and VS.
The M5V is
pre-adjusted and fixed. All adjustments are made referenced to Chassis Ground.
Use “Full White Raster” 100 IRE.
VS: VR901
VA:
VR502
POWER SUPPLY: BASIC OPERATION
AC Voltage is supplied to the
SMPS Board at Connector SC101 from the AC Input assembly. Rectified by the
Bridge rectifier D101 generates a primary B+. The Power factor circuit
generates a Primary supply which can be read at Fuse F302 160V. This primary
voltage is routed through T301 and routed to the Standby 5V supply. The STBY5V
(standby) is B+ for the Controller chip on the back of the board (IC701) on the
SMPS and output at P813 pins 13 and 14 then sent to the Main board for
Microprocessor (IC1) operation (STBY 3.49V RUN 5.23V).
When the Microprocessor (IC1)
on the Main Board receives a “POWER ON“ Command from either the Power button or
the Remote IR Signal, it outputs a high (2.43V) called RL_ON at Pin 15
of P813. This command causes the Relay Circuit to close both Relays RL101 and
RL103 routing AC to the Bridge Rectifier D101 which then routes the primary
voltage to the PFC circuit (Power Factor Controller) 390V which can be read
measuring voltage at Fuses F302 (390V) and F801 (389V) from “Hot”Ground. AC
Detection (AC Det) is generated on the SMPS, by rectifying a small sample of
the A/C Line and routed to the Controller (IC701) where it outputs at P813 pin
16(4.45V) and sent to P301 to the Main Board where it is sensed and monitored
by the Main Microprocessor (IC1). If AC Detis missing the set will come on, but
shut off in 10 seconds.
When RL_ON arrives,
the run voltage +5V source becomes active and is sent to the Main Board via
P813 (5.24V at pin 5, 6 and 7). The (Error Det) from the SMPS Board to the
MainBoard can be measured at pin 8 of P813 (2.88V STBY and 4.93V RUN), but it
is not used. The RL-ON command also turns on the 17V (Audio B+ 16.79V)
which is also sent to the Main Board. The 17V Audio supply outputs to the Main
board at P813 pins 1 and 2 and used for Audio processing and amplification.
The next step is for the
Microprocessor IC1 on the Main Board tooutput a high (3.27V) on M_ON Line
to the SMPS at P813 Pin 17 which is sensed by the Controller IC701, turning on
the M5V line and outputs at P811 pins 9 and 10 to the Y-SUS board.
The Controller (IC701) also
uses the M_ON line to turn on the VA and the VS supplies. (Note there is
no VS On Command in this set). VS is output at P811 to the Y-SUS board P201.
(VA pins 6 and 7 and VS pins 1 and 2). Note: The Va is fused on the Y-SUS then
routed out P209 to the X-Board Left. VS is also routed out of the Y-SUS P206
pins 1 and 2 to the Z-SUS P2.
AUTO GND Pin 18 of P813:
This pin is grounded on the Main board. When it is
grounded, the Controller (IC701) works in the normal mode, meaning it turns on
the power supply via commands sent from the Main board. When AUTO GND is
floated (opened), it pulls up and places the Controller (IC701) into the Auto
mode. In this state, the Controller turns on the power supply in stages
automatically. A load is necessary to perform a good test of the SMPS if the
Main board is suspect.
Va & Vs ADJUSTMENTS
Important:
- Use the Panel Label Not this book for all voltage adjustments.
- Use Full White Raster “White Wash”
Example Voltage Label
- Vs Adjust: Place voltmeter on VS TP. Adjust VR901 until the reading matches your Panel’s label.
- Va Adjust: Place voltmeter on VA TP. Adjust VR502 until the reading matches your Panel’s label.
