LG 42LC46-ZC picture off sound ok

[Jimbo555]

Now I am by no means a technician. Computers I'm ok with. Trying to help a friend.
I have changed all the bad capacitors on the PSU board (7 in all). Checked and checked the soldering and it all looks fine.
The said TV works ok for twelve minutes from cold, then picture goes off and sound remains. It switches on or off fine. I have replaced the P S Board (reputable second hand spares company) and the problem is still there. I have also changed the T-Con board. I have read most of the other forum posts relating to this problem but haven't found anything else I can try or a solution. Any help/suggestions would be appreciated.

Thanks Jimbo

[ReeceyBurger123]

Re: LG 42LC46-ZC picture off sound ok

Does the backlight go out ?

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

Yes

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

If I turn it off after the picture goes and back on after two or three minutes it is perfect again for a couple of minutes.

[vinceroger69]

Re: LG 42LC46-ZC picture off sound ok

can you post good clear pictures of all the boards used in your tv, also on the psu can you take all the voltage readings whilst the set is working and when the set turns it self off also post the readings for us to see which if any voltages are bad etc
ie connector 1 pson 5v tv on 5.3v tv off 5.3v

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

Will post more pics on Mon afternoon but here's the PSU board. As for volt readings I've a little more to learn yet. Thanks for everyone's help

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

Sorry been working a few days. Back to the tv now. On further investigation the back light stays on when the picture goes and sound is ok. Hope the pics are ok and someone can point me to where to check the voltages. Last pic is the connector from the PSU to the main board. Thanks for any help

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

Got some voltage readings. Attached pdf file. Thanks hope someone helps.

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

Voltage readings from two connectors from PSU boardm to Main board.

10 pin connector PSU to main board Voltage readings.
Picture fine Picture off/sound ok Backlight still on
GND
12V 12.12 and 12.09
GND
3.4V 3.42 and 3.41
GND
6.5V 6.34 and 6.34



19V 19.24 and 19.24


13 pin connector PSU to main board Voltage readings.
Picture fine Picture off/sound ok. Backlight still on
3.4V 3.43 and 3.43
ON
GND
6.5V 6.34 and 6.34
A-DIM
GND
ST5V 4.84V and 4.84
BURST
-DIM
ERR
INY
CTR
GND
ST5V 4.84 and 4.84
ON/OFF
ACD

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

Anyone any ideas with these readings. Thanks

[vinceroger69]

Re: LG 42LC46-ZC picture off sound ok

on the 13 pin connector some of the other pins should have voltage on them too have you tested these?

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

No but I will tomorrow.

[vinceroger69]

Re: LG 42LC46-ZC picture off sound ok

if you can please in the working and non working state.

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

13 pin connector PSU to main board Voltage readings.
Picture fine Picture off/sound ok. Backlight still on
3.4V 3.43 3.43
ON
GND
6.5V 6.34 6.34
A-DIM 3.4 3.25
GND
ST5V 4.84 4.84
BURST
-DIM 3.27 3.28
ERR
INY 4.69 4.69
CTR 3.01 3.00
GND
ST5V 4.84 4.84
ON/OFF 2.74 2.75
ACD 4.92 4.93

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

More readings:
13 pin connector PSU to main board Voltage readings.
Picture fine - Picture off/sound ok. Backlight still on
3.4V 3.43 - 3.43
ON
GND
6.5V 6.34 - 6.34
A-DIM 3.4 - 3.25
GND
ST5V 4.84 - 4.84
BURST
-DIM 3.27 - 3.28
ERR
INY 4.69 - 4.69
CTR 3.01 - 3.00
GND
ST5V 4.84 - 4.84
ON/OFF 2.74 - 2.75
ACD 4.92 - 4.93

[vinceroger69]

Re: LG 42LC46-ZC picture off sound ok

on the tcon board there will be a fuse can you check the voltage to each side of the fuse when the tv is working and when the tv is not.

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

Sorry Vinceroger can't see a fuse on the T-Con board. See pic in post 12.

[vinceroger69]

Re: LG 42LC46-ZC picture off sound ok

there is a fuse says f1 with a tk printed on it above printing that says vin 12 volts by the lvds lead be carefull not to slip and short anything out we just want to see if the voltage goes when the picture goes off check both sides of fuse too just in case.

[Jimbo555]

Re: LG 42LC46-ZC picture off sound ok

Great I see that but where do I put the negative.

[vinceroger69]

Re: LG 42LC46-ZC picture off sound ok

on tv metal chassis will do you should see 12 volts i wonder if thats dropping when the tv goes off