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Old 07-15-2020, 07:12 PM   #1
Biruslapio
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Join Date: Nov 2013
City & State: SC
My Country: Brasil
Line Voltage: 220V 60Hz
I'm a: Student Tech
Posts: 156
Default 42PG20R Firmware issue

Hi, This TV has corrupted firmware, first the TV would power up show a blue-ish static screen, some weird lines, sometimes the menu showed up all weird, and power down, locking up and accepting no more commands.
Unplugged main and did the AUTO_GEN test, it displayed the patterns and worked fine, of course then the problem is with the main.
Then I heated up IC802 and IC803 at the mainboard, since I don't have freeze spray at the moment, now it looks less corrupted but still shuts down in 10 seconds or less, I tried to do a service menu reset quickly before the shutdown, but it didn't change, also no idea if it actually worked.

What I'm doubting here is which Flash chip should I replace, IC802 apparently contains some sort of BIOS within, and IC803 is the software of the TV, all that is sold around here for replacement is IC802, I can't find the flash dump of IC802 also.

IC802 = ATMEL 24C64AN SU27
IC803 = I can't read the label.

The pictures are of front and back of the mainboard, and IC802/803 on the zoomed photo, the yellowed dark spots are flux, there was some minor oxidation that i got rid off.
Attached Images
File Type: jpg P_20200715_194642.jpg (934.9 KB, 5 views)
File Type: jpg P_20200715_194659.jpg (850.1 KB, 5 views)
File Type: jpg P_20200715_194523.jpg (2.55 MB, 4 views)
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Old 08-17-2020, 03:44 AM   #2
Biruslapio
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Join Date: Nov 2013
City & State: SC
My Country: Brasil
Line Voltage: 220V 60Hz
I'm a: Student Tech
Posts: 156
Default Re: 42PG20R Firmware issue

Update: I've bought 2 pieces of IC802 and IC803 each, they already were flashed with the proper dump since I couldn't find anything online to flash them myself.

Nothing changed initially, the symptoms were > TV powers on by itself, the TV background (everything except the menus) would be all blue, purple, green, red, yellow, each time one color, then the TV would stop accepting remote input, picture freezes and weird verticals stripes would show, shut down, repeat.

Then I started probind around the TV with an oscilloscope looking for noisy lines at filtering capacitors, all the rails except the PSU ones were noisy, but that apparently is normal on this TV, I was seeing some spikes on C1118 C1128 and C1110, searched at forums further and did what I should've done at first, replace the 100uF 16V SMD solid capacitors at the VRAM and other rails, this stopped the erratic behavior of shutdown and menu corruption, but the background is now green coloured and HDMI only shows messed up artifacts.

I swapped IC802 once again and the TV finally worked, this is a universal issue on the whole XXLG and XXPG series from LG in 2008, every board has these capacitors start failing over years of use and introducing noise at the VRAM and EEPROM VCC, then when the TV shuts down it corrupts the IC802 flash contents and the image loses all their original config so a random color mix is selected as white, sometimes blue/red/green etc.

The TV didn't last 1 hour before having another problem, the black turned to blue (even the menus), and vertical lines appeared at regular intervals on the screen, after wasting a lot of time replacing even more capacitors on the main board, I unplugged LVDS from main board and did the AUTO_GEN test, the blacks weren't blue, but the vertical lines appeared on the test, so I simply swapped the logic board with another one I luckily had lying around in better condition from a 42PG60D, it was identical except for the memory software version, this finally seemed to fix it, I could've also replaced the caps on the original logic board, but didn't bother with it.

Messing with IC803 is useless, IC802 and the capacitors are where the issue lies. The .bin flash dumps for both of them are attached.

Caps replaced:
C1118 C1128 C1110 100uF 16V next to DDR chips.
C1143 47uF 16V < Weren't necessary
C1109 C1153 100uF 16V
Attached Files
File Type: zip IC 802 and IC803 42PG20R.zip (504.7 KB, 6 views)

Last edited by Biruslapio; 08-17-2020 at 03:47 AM..
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