Thursday, November 12, 2015

LG 47LE8500 POWER SUPPLY AND LED INVERTER TEST

LG 47LE8500 


POWER SUPPLY AND LED INVERTER TEST 

POWER SUPPLY SECTION
This switch mode power supply develops Stand By 3.5V at all times when AC is applied. At power on, it develops 12V and 24V for the Main board And 24V for the Inverters

This power supply draws less than 1 watt during stand by mode. The fuse F501 reads 159.6V
(from hot ground) during this time. (F101 is <3V) When the controller chip receives the PWR-ON command 3.3V via P201 Pin 1, the primary section increases its current supplying ability. Both Primary fuses F101 and F501 now read a little more than 390V.
P201 Connector: (To Main Board)
12V is routed out P201 pins 17, 19 and 21 and
24V is routed out P201 pins 2, 3 and 4.
P204 Connector: (To Inverter Main Board)
24V is routed out P204 pins 1 through 5.
P205 Connector: (To Inverter Secondary Board)
24V is routed out P205 pins 1 through 5.
Power Supply Board Low Voltage Test 1

AC Should not be applied at any time while adding jumpers or While unplugging connectors as damage to the circuit Board may occur.
a) When AC is applied, the SMPS “MUST” be producing STBY 3.5V on pins 9, 10, 11 or 12 of P201.
If 3.5V Standby is not being generated, the SMPS is defective and must be replaced. There is no need to continue with the next test. But, make sure AC is arriving at the connector SK101.
(b) Unplug P8000 on the Main Board to make insertion of the Jumpers easier. Use P700 Side to insert resistors
TEST 1:
No Backlights during this test

(1) Add a jumper between (3.5V STBY) pin 7, 8, 9 or 10 and Pin 1 (PWR_ON). Apply AC.
This will turn on the power supply, relays will click.
a) Check that the 24V and 12V power supplies are turned on,
# P201 (12V pins 17, 19 and 21)
# P201 (24V pins 2, 3 and 4)
# P204 and P205 (24V pins 1 through 5) to the Inverters
Power Supply Board Backlights Test 2
Continue if the 1st test was OK. Leave original jumper in place.

(3) Add another jumper between (STBY_3.5V) pin 9, 10, 11 or 12 and Pin 18 (INV_On).
(4) Apply AC Power. Simulating a Power and Backlight On command.
Backlights Normal:
a) If normal, the backlights should turn on. SMPS OK, Inverter OK.
Backlights Abnormal:
a) Recheck all connections.
b) Confirm the INV On/Off line pulling up to at least 3V and arriving at both Inverters.
c) Check the connections to the Inverters.
If the 24V and the Inverter On command is arriving at the Inverters in, check Inverter Section.
Note: Either Inverter can run separately.
Power Supply Connector P201 Voltage Check
Pin
Label
STBY
Run
24
ERROR
0V
0V
23
n/c
n/c
0V
22
n/c
n/c
0V
21
12V
0V
11.9V
20
(1) P-DIM
0V
0.37V~3.3V
19
12V
0.42V
11.9V
18
INV-ON
0V
2.92V
17
12V
0V
11.9V
16
n/c
n/c
n/c
13-15
Gnd
Gnd
Gnd
9-12
3.5V
3.45V
3.44V
5-8
GND
GND
GND
2-4
24V
0V
24.6V
1

PWR-ON

0V

3.3V

(1) PDIM Pin 20 can vary according to incoming video IRE level, OSD Backlight setting and then Intelligent Sensor (room light condition) Output from the Video Processor IC900. Range 0.37V to 3.3V.
INVERTER (LED BACKLIGHTS) SECTION
The Inverter (Main) receives 24V from the SMPS on CN1 pins 1>5 and Inverter (Secondary) receives 24V on CN101 pins 1>5. The Inverter On (INV ON) command arriving on CN1 or CN101 pin 12 starts the Inverter drive signals, (120Hz).
P-DIM is delivered from the Main board through the SMPS to the Inverter on CN1 or CN101 pin 11.
The Inverters are responsible for delivering B+ approx. 13V to each of the 216 LED Blocks. This is accomplished by 3 DC to DC Converters, 2 on Inverter (Main) and 1 on Inverter (Secondary) 
Inverter (Main) 13V
# U101, Q4, Q5, L101 and C75, out CN2 and CN3.
# U102, Q7, Q8, L102 and C89, out CN4 and CN5.
Inverter (Secondary) 13V
# U101, Q105, Q106, L206 and C151, out CN104 and CN105
The Inverters must also deliver grounding pulses (Drive Signals) to each of the 216 LED Blocks.
This is accomplished by the 15 switching components, 10 on Inverter (Main) U3>U11 and U13 and 5 on Inverter (Secondary) U2>U5 and U13
Inverter (Main) has 4 Connectors CN2 > CN5 that connect to Extensions boards. The Left hand Extension board (as viewed from the rear) connects to CN2 and CN3 and the Center Extension board connects to CN4 and CN5.
Inverter (Secondary) has 2 Connectors CN104>CN105 that connect to the right hand Extension board (as viewed from the rear) which connects to CN23 and CN24. Each Extension board has 9 connections to the Backlight LEDs. There are 4 LEDs per/block, 216 Blocks, 8 Blocks per/cartridge, 3 Cartridges per/bar, 9 bars (rows), 32 LEDs per/cartridge, 96 LEDs per/bar. With a total of 864 LEDs
IOP Structure
4 LEDs per/block (216 Blocks) 8 Blocks per/cartridge, 9 bars with 3 cartridges per/bar,
32 LEDs per/cartridge, 96 LEDs per/bar. 864 LEDs total.

The Individual LEDs can be checked using the Diode Mode forward bias test. The LED will light.

47LE8500 IOP Block Structure 

Explode View of the IOP Panel LG

1. Case-Top Ass’y
2. TFT Panel Ass’y
3. Guide Panel
4. Sheet DBEFD
5. Sheet Prism U
6. Sheet Prism L
7. Sheet Diffuser L
8. Plate Diffuser
9. Cartridge Ass’y
10. Cover Bottom
11. Driver Boards (2)
12. Extension Boards (3)
13. FRC

 Circuit Board Layout
Inverter LED Driver Information
The Inverters deliver grounding pulses (Drive Signals) to each of the 216 LED Blocks. This accomplishes Global Dimming and Local Dimming. Each output is labeled Vxx. Grounding each block is accomplished by the 15 switching components, 10 on Inverter (Main) U3~U11 and U13 and 5 on Inverter (Secondary) U2~U5 and U13. Inverter (Main) has 4 Connectors CN2~CN5 that connect to Extensions boards. The Left hand Extension board (rear view)connects to CN2 and CN3 and the Center Extension board connects to CN4 and CN5.