LG 42LG3000 TV Board needs replacing, but which one?

[plug1]

Nice first post bud , you should introduce your self on the mew members forum .and read the rules ect.
we get a lot of leaches .

And members from 5 years ago with one post .
lol.

[Percy Sugden]

Looks very much like a duff CCFL tube in the screen causing it to shut down.

Had it many times on this and other LGs from 2008/9 - it's very common.

[DejaVu]

Looks very much like a duff CCFL tube in the screen causing it to shut down.

Had it many times on this and other LGs from 2008/9 - it's very common.

Dam! More spanners in the works.

[ozy]

these sets don't normally suffer from ccfl failure, they do how ever suffer from back light failiure due to the 2 ccfl connector boards (the long boards that run down either side inside the lcd panel that the ccfl clip into) there are about a dozen 16kv caps on each board, these cook and have been known to burn through the board, when these fail they give off a strong smell.

The fact the power led only glows dim suggests to me its not a backlight problem, but more likely psu or main ssb.

Might be worth removing C108 ZD111 and ZD112 in the protection circuit on psu , this can cause some weird and wonderfull fault according to lg's service bullitin

[DejaVu]

Major update on this thanks to the input from the BadCaps lads... AD, dam right them boys know their shit!

Managed now to get the TV on with 'The Fly' for a few seconds. Turns out (or so I think so far) the Slave Invertor board is dead. With it unplugged the Master fires up no problem, but TV shuts down after a few seconds once it realises the Slave is not responding!!

WELL PLEASED!!

Hoping they can help fault find the knackered component on the board rather than replacing it!

[AD]

Glad your having luck with it DejaVu..

Mine is another story

[ozy]

is it a VIT71053.55 inverter ?
if so check fuse on inverter, check the 3 electrolytic caps, also check the mosfets according to my notes I changed 2 mosfet P1504EDG (p-channel) and P2504EDG (n-channel) that was short circuit, if they all check ok compare the resistance of the two transformers.

[DejaVu]

It's a VIT71053.51 (can I swap them for .54 & .55 if it comes to it?)
They look almost identical, but things in different places.

My actual board (image wont embed) Click to Zoom -
https://www.dropbox.com/s/ou2q97ka2l...2022.13.13.jpg

The VIT71053.55
http://tvpartsfixit.co.uk/Images/Parts/319.jpg

Already checked the surface mounted fuse. Continuity is fine.

Visual condition of the 3 caps look OK.
Not sure how to test them properly though, can it be done with a DMM?

I've gone through all the Mosfets and all seem fine.
No shorts as far as I can tell, although not 100% sure I checked them correctly - will go again.
Used this vague/slightly confusing description on how to do it from here - http://www.badcaps.net/forum/showthr...952#post241952

Using the Left hand leg (Gate) and earthing to the Frame, each reading is '1.' on all 4 Mosfets.
Using the Right hand leg with the Center pin gives the same results.

The resistance from the Transformers (using pins 9 & 12) seem a little strange but the same results on the Master (working) and the Slave are the same...

Master
https://www.dropbox.com/s/dex5ce1ba91gwwk/Master.jpg

Slave
https://www.dropbox.com/s/9xkzl4i6x32qj0z/Slave.jpg

But again, maybe doing this wrong too. DMM was on 20K Ohms when measuring.

Well - it feels like progress anyway!
http://www.youtube.com/watch?v=0ayUhUQm0mQ

[DejaVu]

Read up that the .54 & .55 are more reliable and compatible replacements for .50 & .51.
Can get the pair for £17. Should I go for it?

[ozy]

at that price I would defo change the pair, and yes they are compatible as long as changed as a pair.
could still be the ccfl/ccfl boards in the lcd, have a sniff in the rear left and right of lcd panel and see if there is a strange tcp sort of smell, unless you have a zippy or other ccfl tester the only way to tell would be to swap the inverters.

[DejaVu]

Purchased.
Everything crossed now...!

Let ya know what happens.

Sent from my GT-I9300 using Tapatalk 4

[DejaVu]

Got both Invertors today.
Fitted them, TV now comes on. Stays on for 3 seconds and turns off still.

The left hand side still looks a little dark compared to the right.
Clearly did need the Slave Board and looks like it;s now doing what it should - with both boards fitted.

I'll upload a video of the state of play in a little while.

[DejaVu]

Still got the back off this thing, not had the time to work on it lately, but found some tonight.
Ordered the Invertor boards and replaced them. Now I'm getting this with both invertors installed. Still looks like the Slave is struggling to me, but hoping it's something else now.

http://www.youtube.com/watch?v=GXI2qxzBR8I

[ozy]

seeing as you have changed the inverters it only leaves the ccfl's in the lcd panel, seeing as its dark down the whole left side I would suspect the 18 15pf 6kv caps on the board the ccfl's clip into inside the lcd panel. These boards are not available on there own but you can carefully disassemble the panel remove all 18 ccfl's and remove the connector board and change the caps on it, they are a pain to do as they are normally glued to the pcb as well.