LG 32LN 540B TV Sound but no video

[CostasCostas]

My wife recently fell from a chair whilst "spring cleaning" and splashed our LG TV with the contents of a nearby mop bucket. Not much water and only on the screen.

We left the TV for a few days to "dry out" but all we have is sound and no video. The backlight seems fine but no picture.

The TV is an LG 32LN 540B.

Google suggests this is quit often a problem with the t-con board and I have attached a photo to this post. The part reference is 6870C - 0442B and as far as I can tell from the various test points on the board it checks out OK.

Also attached is the power board, EAX64905001, and again the voltages seem to check out on P201 from the top as 0, 12, 12, 0, 25, 0, 3, 3 and 3.

Finally the video board is NC4.0/LD36B, attached, but I don't have a clue what to check on this board. Obviously some of it works as the power board feeds the video board which in turn feeds the t-con board.

Any ideas how I can work out what part of the TV is broken?

[dick_barton]

Re: LG 32LN 540B TV Sound but no video

You could check what DC voltage you have on both sides of the smd device marked TK closeby CN1 (picture 1)

[CostasCostas]

Re: LG 32LN 540B TV Sound but no video

@dick_barton the voltage is 11.92 on either side of TK. Presumably this is OK.
Anything else I can try?

[dick_barton]

Re: LG 32LN 540B TV Sound but no video

Yes that's OK. Is the tcon at the bottom of the set?

[CostasCostas]

Re: LG 32LN 540B TV Sound but no video

Yes with the infrared sensor directly below it. Power board is centre left and video board centre right.

[dick_barton]

Re: LG 32LN 540B TV Sound but no video

The Tcon has quite a number of test points you could measure.
If you could list them I'm sure someone can tell you if the Tcon appears to be OK or faulty
VCC, VCC_ 33, VGH, P12, HVDD etc.

[dick_barton]

Re: LG 32LN 540B TV Sound but no video

There will also be a narrow interface circuit board which the tcon connects to that is attached to the led panel. This may still have water on it. There is also a possibility that if there are smd fuses on these boards which also need to be checked out.

[vinceroger69]

Re: LG 32LN 540B TV Sound but no video

yes as above post water may of got onto the lcd panel pcb or even the lcd tab bond area so wort stripping down and having a close look.

[CostasCostas]

Re: LG 32LN 540B TV Sound but no video

I had checked the obvious 3.33 and 12V but looking at the full set it doesn't look right.
This is what I have:
VCC 3.3
VCC_33 3.3
VGH 0
P12V 11.89
HVDD 0.96
VIN 11.89
VDD 0.30
VGL MINUS 5
WP 3
SCL 3.3
SDA 3.3
SOE 0.66

Is the t-con dead? Can I repair it or do I just replace it?

[vinceroger69]

Re: LG 32LN 540B TV Sound but no video

depends you need to check the long lcd panel pcb first for water damage blown fuses etc as this may cause voltage issues on the tcon etc its the pcb the lower ribbon cable of the tcon joins onto.

[CostasCostas]

Re: LG 32LN 540B TV Sound but no video

@dick_barton is the interface board what a layman like me would call the infrared sensor board? Tried with and without the infrared sensor board connected. Does it need to be connected i.e. should the TV work from the physical buttons on the TV?

@vinceroger69 what does the "lcd panel pcb" and the "lcd tab bond area" look like?

[vinceroger69]

Re: LG 32LN 540B TV Sound but no video

see below post as its explaned better with a picture

[dick_barton]

Re: LG 32LN 540B TV Sound but no video

The two ribbon tabs go to thin printed circuit boards which are then attached to the lcd panel via more flexible ribbon tabs. The circuits boards run along the length of the LCD panel.
You need to take extreme care when handling the circuit boards so that the ribbons are not damaged or pulled away from either the circuit board or the LCD screen. If this happens then the set has had it.

[dick_barton]

Re: LG 32LN 540B TV Sound but no video

I had checked the obvious 3.33 and 12V but looking at the full set it doesn't look right.
This is what I have:
VCC 3.3
VCC_33 3.3
VGH 0
P12V 11.89
HVDD 0.96
VIN 11.89
VDD 0.30
VGL MINUS 5
WP 3
SCL 3.3
SDA 3.3
SOE 0.66

Is the t-con dead? Can I repair it or do I just replace it?

What do you have for VGH_L, VGH_F, ODD, EVEN


It looks like you have a problem with VGH missing, but if someone else can please confirm.

[vinceroger69]

Re: LG 32LN 540B TV Sound but no video

What do you have for VGH_L, VGH_F, ODD, EVEN


It looks like you are missing VGH but if someone else can please confirm.

a quick read of this link looks like vgh should be 27v for a 32 inch set
http://tvrepairsolution.blogspot.co....lcd-panel.html

[dick_barton]

Re: LG 32LN 540B TV Sound but no video

a quick read of this link looks like vgh should be 27v for a 32 inch set
http://tvrepairsolution.blogspot.co....lcd-panel.html

Yes, I've seen VGH given between 15 to 30V and VGL between -5 to -15V

[vinceroger69]

Re: LG 32LN 540B TV Sound but no video

maybe waters got onto that panel pcb and shorted a cap/etc out etc dragging vgh down?

[CostasCostas]

Re: LG 32LN 540B TV Sound but no video

I'll see if I can find VGH_L, VGH_F, ODD and EVEN but I don't recollect seeing them on the t-con.
I'll also check out the LCD panel board.
Thought I had already stripped down the TV

[dick_barton]

Re: LG 32LN 540B TV Sound but no video

With a bit of luck it may only be a faulty Tcon damaged like you say when water was splashed and with all likelihood shorted some components on the panel tab pcb. Hopefully nothing else is damaged.

[dick_barton]

Re: LG 32LN 540B TV Sound but no video

I'll see if I can find VGH_L, VGH_F, ODD and EVEN but I don't recollect seeing them on the t-con.
I'll also check out the LCD panel board.
Thought I had already stripped down the TV

They are shown in your first picture.