LG 42LC46 problem

[tom66]

Re: LG 42LC46 problem

I,ve borrowed a Fluke 77 series II multimeter will this be better in testing than mine..thx

It would be better if you could borrow an oscilloscope... even a basic 20 MHz analogue one will be able to do a go/no-go on the LVDS waveforms. (I've used one before to check if they were present and they appear as a sine wave.)

[sienoki]

Re: LG 42LC46 problem

I tried reflowing on both boards too no avail againthe original board had the best results as it only flickered for a few mins the replacement board board no change..
With the back off & the tv on for a while i put my hand near the heat sinks on power supply to feel how warm they where and got a shockafter your advice and reading graham01 expereince dont think reflow is working although the original board had good results

Any chance of you looking at the main board maybe a reball if i posted to you..ive fixed numerous xboxes & ps3s with reflows but never a reball..i wish i could afford the equipment..maybe when kids have grown up..ha

I,ve borrowed a Fluke 77 series II multimeter will this be better in testing than mine..thx

[sienoki]

Re: LG 42LC46 problem

Well, I'm not sure any more.

There are really no other boards that could cause this problem. You can reflow the board safely as long as temperature is kept around 230°C with a ramp rate of at most 4°C/second. This may or may not work. I'm not holding out hope.

You could also have a bad panel, but I've never seen that pattern appear with a bad panel.

Maybe the power supply is bad but it's showing itself in an obscure fashion. Check for cold solder joints.

I wish I could be more help.

I'm guessing you don't have a scope?

I tried reflowing on both boards too no avail againthe original board had the best results as it only flickered for a few mins the replacement board board no change..
With the back off & the tv on for a while i put my hand near the heat sinks on power supply to feel how warm they where and got a shockafter your advice and reading graham01 expereince dont think reflow is working although the original board had good results

Any chance of you looking at the main board maybe a reball if i posted to you..ive fixed numerous xboxes & ps3s with reflows but never a reball..i wish i could afford the equipment..maybe when kids have grown up..ha

[tom66]

Re: LG 42LC46 problem

Well, I'm not sure any more.

There are really no other boards that could cause this problem. You can reflow the board safely as long as temperature is kept around 230°C with a ramp rate of at most 4°C/second. This may or may not work. I'm not holding out hope.

You could also have a bad panel, but I've never seen that pattern appear with a bad panel.

Maybe the power supply is bad but it's showing itself in an obscure fashion. Check for cold solder joints.

I wish I could be more help.

I'm guessing you don't have a scope?

[sienoki]

Re: LG 42LC46 problem

Oh dear, another reflow problem. Graham01 had a plasma with this problem and he reflowed the board about 10 times in all, every time it would fix it but it then died after 30 mins or so, unfortunately oven reflows don't always work and eventually the board died completely...

Try applying pressure to the large processors and see which one restores the picture.

I bought another main board not from ebay but from EMO,s tv..he said the board had been fully tested so thought id give it a go..

Same results 10mins good picture then 10mins flickering then good picture all day..the only part ive not changed as yet is LDVS connector..

Can i be 100% sure its heat related with cold solder joints with it being non lead..i want to try and bake the main board in oven but with both sides of the board being covered with smd,s am a little worried about parts dropping off from underneath..
Since ive now 2 main boards & 2 t-cons boards im pushing myself to put them in the oven and would really appreciate on the correct way of doing this..thx

[tom66]

Re: LG 42LC46 problem

Has any1 tried an oven bake with a main board?..if so what would be the correct way of doing this...thx

Oh dear, another reflow problem. Graham01 had a plasma with this problem and he reflowed the board about 10 times in all, every time it would fix it but it then died after 30 mins or so, unfortunately oven reflows don't always work and eventually the board died completely...

Try applying pressure to the large processors and see which one restores the picture.

[sienoki]

Re: LG 42LC46 problem

i had nowt to lose so i thought id do a full reflow of main board both sides..after 15mins the screen flickered for about 5mins then picture has been great for over 1hr so farit didnt lose picture like before after 10mins..

To get rid of that flicker all together does any1 know at what temperature the board would be needed to do a reflow..as i just used my heatgun for approx 2mins either side..doing 1 side then let cool down for 10mins before doing the other..thx

Has any1 tried an oven bake with a main board?..if so what would be the correct way of doing this...thx

[sienoki]

Re: LG 42LC46 problem

Thx tom for help and patience in my matter...its just a shame as ive found the promatic area with ur help and been stuck there for further testing..
This site is awsome for helping diagnose etc and without help from urself and others there would be more tv sets a local dump..once again thx for all ur help fella..

i had nowt to lose so i thought id do a full reflow of main board both sides..after 15mins the screen flickered for about 5mins then picture has been great for over 1hr so farit didnt lose picture like before after 10mins..

To get rid of that flicker all together does any1 know at what temperature the board would be needed to do a reflow..as i just used my heatgun for approx 2mins either side..doing 1 side then let cool down for 10mins before doing the other..thx

[sienoki]

Re: LG 42LC46 problem

Try offering the seller a lower price, many would rather sell a board for half price than none at all.

I would sell the TV as is, then look at the council dump for another one (a great source of my TVs, and they're often only bad caps at fault.) I got the LG 42LC46 in my living room from there, for just £20.

Thx tom for help and patience in my matter...its just a shame as ive found the promatic area with ur help and been stuck there for further testing..
This site is awsome for helping diagnose etc and without help from urself and others there would be more tv sets a local dump..once again thx for all ur help fella..

[tom66]

Re: LG 42LC46 problem

Theres a board on ebay 56quid all in..i dont want to spend that much more on it..that will be 145quid for a 42" lcd not bad i suppose but without schematics my testings ends here as havnt got a clue what to do now..thx

Try offering the seller a lower price, many would rather sell a board for half price than none at all.

I would sell the TV as is, then look at the council dump for another one (a great source of my TVs, and they're often only bad caps at fault.) I got the LG 42LC46 in my living room from there, for just £20.

[sienoki]

Re: LG 42LC46 problem

Hi tom..ive searched in vain for a service manual but to no avail..i heard somewhere about a german site who might have 1..but stuck on that 1..
These are markings on board
CHASSIS:LD/PD73/75A
EAX35231403(0)..thx

Theres a board on ebay 56quid all in..i dont want to spend that much more on it..that will be 145quid for a 42" lcd not bad i suppose but without schematics my testings ends here as havnt got a clue what to do now..thx

[sienoki]

Re: LG 42LC46 problem

I don't think the capacitor is faulty. Rather, what is feeding it is faulty.

I can't find the service manual, unfortunately. Are there any part #s on the motherboard?

Hi tom..ive searched in vain for a service manual but to no avail..i heard somewhere about a german site who might have 1..but stuck on that 1..
These are markings on board
CHASSIS:LD/PD73/75A
EAX35231403(0)..thx

[tom66]

Re: LG 42LC46 problem

I don't think the capacitor is faulty. Rather, what is feeding it is faulty.

I can't find the service manual, unfortunately. Are there any part #s on the motherboard?

[sienoki]

Re: LG 42LC46 problem

I have to go to work now..bus driver crap hrs..ive 6days off next week so i will report bk with that part no and other voltage readings..thx

6 days off nowso hopefully i can try and get this tv fixed..fingers crossed anyways
That part no for LDO is EH14A-647J22 and the readings where 0.00..2.48..4.83
I tested 10 small caps..5 where marked 72k-100-16v..the other 5 are k6p-22-16v..(G)when picture good(B)when picture bad
C975-100-16v=(G)1.77(B)1.54
C959-100-16v=4.83/4.83
C971-100-16v=2.49/2.49
C852-100-16v=2.49/2.49
C853-100-16v=1.24/1.24
C1708-22-16v=1.77/1.53
C803-22-16v=2.49/2.49
C796-22-16v=2.49/2.49
C822-22-16v=2.49/2.49
C727-22-16v=2.49/2.49
I resoldered all the caps to make sure and the only 2 that are dropping are C975 and C1708..will these 2 caps need replacing? if so can any1 reccomend which 1s to get..thx

[sienoki]

Re: LG 42LC46 problem

Is that 2.48V? What is the device part #?

You could reflow it, try and see, but I don't think that's the problem. But just to confirm, probe the voltages on the nearby caps around that regulator, and see they change, some should be 4.38V and some should be 2.48V, if the voltage disappears suspect a bad joint.

I have to go to work now..bus driver crap hrs..ive 6days off next week so i will report bk with that part no and other voltage readings..thx

[tom66]

Re: LG 42LC46 problem

The readings are left leg 0..middle leg 248..right leg..483
these readings are the same after screen failure..can a reflow of that area be done..i have non clean flux and a heat gun..thx

Is that 2.48V? What is the device part #?

You could reflow it, try and see, but I don't think that's the problem. But just to confirm, probe the voltages on the nearby caps around that regulator, and see they change, some should be 4.38V and some should be 2.48V, if the voltage disappears suspect a bad joint.

[sienoki]

Re: LG 42LC46 problem

Check the regulator before & after failure, looks like you have found the suspect component. These LDOs, when they fail, can become temperature sensitive.

The readings are left leg 0..middle leg 248..right leg..483
these readings are the same after screen failure..can a reflow of that area be done..i have non clean flux and a heat gun..thx

[tom66]

Re: LG 42LC46 problem

Check the regulator before & after failure, looks like you have found the suspect component. These LDOs, when they fail, can become temperature sensitive.

[sienoki]

Re: LG 42LC46 problem

Hi tom..i did another hair dryer test as i feel its heat related now..after picture goes off i warmed up main board and in 1 area BINGO the picture re-appears..

Is this a failing element or solder issues..im borrowing a descent camera later so i can zoom close in and send pictures..thx

Hi these r the close ups..its the area around the IC902..thx

[Paul678]

Re: LG 42LC46 problem

I would try re-soldering all the pads around that
one problem area....