LG 42ln578v-ze problems

[jmh474]

Im starting up my own electronics repair business fixing tv, laptops and such like on the side as well as working as an electrician's mate, im not advertising im just asking for help please, as iv been handed a tv and im a little stumped.

The TV comes on fine but i have no sound or picture, the back light comes on!

Iv check all the output V on the main board and there fine, power going to where it should be.

So im thinking its the T-con board but i was under the impression that if thats the case the TV go's into like a self protect mode and wont turn on.

Any help would be grate thanks

[Andrew F. Ali]

Re: LG 42ln578v-ze problems

So you are getting 5Vdc st-by voltage on the Power Bd??

[jmh474]

Re: LG 42ln578v-ze problems

yes

[Andrew F. Ali]

Re: LG 42ln578v-ze problems

Look on the T-CON Bd and see if you can find the Fuse. Check if you have 5-12Vdc on each side of the Fuse.

[budm]

Re: LG 42ln578v-ze problems

Pictures of the board, T-CON board? 12VDC on the T-CON fuse.

[dick_barton]

Re: LG 42ln578v-ze problems

On P201 do you have the following voltages
24V
12V
3.5V
Pwr_ON = ??
DRV_ON = ??
PDIM =? ?

[jmh474]

Re: LG 42ln578v-ze problems

yes voltage at both sides of the fuse

https://www.badcaps.net/forum/attach...1&d=1471375104

[Diah]

Re: LG 42ln578v-ze problems

you wrote that you don't have sound too, T-CON had nothings to do here.. check 24V from the main board side exist or not, if yes main boards faults if no 24v power boards fault

[jmh474]

Re: LG 42ln578v-ze problems

On P201 do you have the following voltages
24V
12V
3.5V
Pwr_ON = ??
DRV_ON = ??
PDIM =? ?


and what voltage do you have at the led output connector P801 which says 157V on the board for 42" set

P201 yes all voltages are read right
P801 is only 70v but back light is on and working fine

[dick_barton]

Re: LG 42ln578v-ze problems

Pwr_On, DRV_ON, PDIM ??????Can you tell us what they measure

[jmh474]

Re: LG 42ln578v-ze problems

you wrote that you don't have sound too, T-CON had nothings to do here.. check 24V from the main board side exist or not, if yes main boards faults if no 24v power boards fault

never listen to customers lol there is sound just checked

[jmh474]

Re: LG 42ln578v-ze problems

Pwr_On, DRV_ON, PDIM ??????Can you tell us what they measure

sorry what is

Pwr_ON
DVR_ON
PDIM

[dick_barton]

Re: LG 42ln578v-ze problems

They are shown on the circuit board. Connection P201.
P_On Power On
PDIM Led dimming
DRV_ON Not sure

[jmh474]

Re: LG 42ln578v-ze problems

Using a bright light can you see a picture or the menu on the screen if you look very carefully.

back light is working i can see the light from the back holes in the tv

[budm]

Re: LG 42ln578v-ze problems

So you have SOUND, you have backlights but no pictures on the screen, 12V is present on the SMD fuse of the T-CON board.
So next thing to do is to have one ribbon cable between the T-CON and the LCD panel connected one at a time to see what you get.

[Diah]

Re: LG 42ln578v-ze problems

never listen to customers lol there is sound just checked

i see LOL then you are close .. waiting your answer on budm test . remain black or there white screen some how.. lol

[jmh474]

Re: LG 42ln578v-ze problems

ok so iv disconnected each ribbon cable

(looking at the back of the TV)

right ribbon disconnected still blank screen

left ribbon disconnected half screen white with other half black and purple lines

[Diah]

Re: LG 42ln578v-ze problems

go deep to the panel taps and check if there water damage or burn before you go to change T-CON

[budm]

Re: LG 42ln578v-ze problems

If you look at the T-CON board, you can see bare copper pads for test points that you need to test some DCV readings, the picture is not clear enough for me to read the label for each one of those test points.

[jmh474]

Re: LG 42ln578v-ze problems

is that any better

no burn or water damage