LG 42LC46 problem

[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

[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.)

[rmoody]

Re: LG 42LC46 problem

I think I have the same set. My scenario is the guy that brought it to me picked it up as a freebie and it wouldn't power on. Well he decided to take the back off and go exploring, he found some bulged caps on the PS so he tried replacing them. He got it to power on but it would shut off after 10 minutes. He brought it in to me and I observed that he had reversed polarity on all 8 of the caps he had replaced not to mention a very shoddy soldering job. I removed and replaced all the caps he replaced. One of the caps he removed in a rough fashion and ripped the solder pad off of the pcb. I tried to make the solder stick but it doesn't look so well. Anyways, the tv now powers on and stays on but the picture is horrible. I have posted pics to try and show the quality. I'm at a loss of if he damaged the PS somewhere causing this or maybe it's the main board or tcon. Any suggestions would be helpful.

[retiredcaps]

Re: LG 42LC46 problem

Any suggestions would be helpful.

I would reseat and clean every connection possible with isopropyl alcohol to see if you get any improvement.

[rmoody]

Re: LG 42LC46 problem

Here's a look at how bad the soldering looked.

[rmoody]

Re: LG 42LC46 problem

I would reseat and clean every connection possible with isopropyl alcohol to see if you get any improvement.

Do you think the power supply could be causing the distorted picture?

[rmoody]

Re: LG 42LC46 problem

Also need to mention that even though the picture is distorted, when I press the menu, it comes up looking great. It kind of makes me feel like it's in the main board as the inputs are what's distorted. Also I think if it were the tcon even the menu would look bad.

[tom66]

Re: LG 42LC46 problem

It's quite possible the EEPROM has become corrupted and in the process has messed up some very important picture settings - common on Samsung TVs with bad caps.

[rmoody]

Re: LG 42LC46 problem

It's quite possible the EEPROM has become corrupted and in the process has messed up some very important picture settings - common on Samsung TVs with bad caps.

Any way to check this without swapping boards? I would think the EEPROM can't just be replaced without being programmed, Right?

[sienoki]

Re: LG 42LC46 problem

Any way to check this without swapping boards? I would think the EEPROM can't just be replaced without being programmed, Right?

Hi there..if ur set is the same model as mine(LG 42LC46) your main board is different to mine..damn that soldering is bad..

[rmoody]

Re: LG 42LC46 problem

Hi there..if ur set is the same model as mine(LG 42LC46) your main board is different to mine..damn that soldering is bad..

Bad isn't the word for what that is, he massacred that board.

[rmoody]

Re: LG 42LC46 problem

I think this is actually a 42LC7D. He brought it to me with the back off so I can't confirm the actual model.

[tom66]

Re: LG 42LC46 problem

Any way to check this without swapping boards? I would think the EEPROM can't just be replaced without being programmed, Right?

Not necessarily... most TVs will reprogram the EEPROM with default factory settings if a blank one is replaced.

[rmoody]

Re: LG 42LC46 problem

Found something interesting. I noticed when powering up the tv the video looked fine for just a second and then it cuts out to no signal for about 10 seconds and comes back on distorted. I started checking some of the pins going to the main board and one stood out, it's the VBR-B. There's a VBR-A that reads 3.3V but VBR-B was only reading 2.7v. I jammed my probe into the VBR-B and powered it on from a cold shut down. When the tv first powers on and the display is good, I get 3.3 volts on the VBR-b pin and then it zeroes out while the no signal was displayed and then when the distorted picture comes back on the voltage is only 2.7V

[rmoody]

Re: LG 42LC46 problem

Well I attempted repairing the missing solder pad today with a circuit writer pen but it didn't help any. I'm pretty sure my problem is from the power supply. The darn things are hard to find too.

[bbjunkie]

Re: LG 42LC46 problem

Could it be repaired? Pace have some really good videos on circuit board repair on youtube. http://www.youtube.com/watch?v=7o4ZWlG6mmo

[rmoody]

Re: LG 42LC46 problem

Could it be repaired? Pace have some really good videos on circuit board repair on youtube. http://www.youtube.com/watch?v=7o4ZWlG6mmo

I watched some of those videos but not sure if the kit will be worth the time and money. It's not mine anyways, since the guy broke it, i'm leaving it up to him to find a board. Do you know where to find those kits? Radio shack is the best thing i've got around here and it's 30 minutes away.

[bbjunkie]

Re: LG 42LC46 problem

I've never looked for them before - perhaps digikey or mouser? I'm on my iPhone right now but will have a look when I return home (out picking up a 42" HD LCD with cracked screen for free - now missus wants to do some shopping!)

[rmoody]

Re: LG 42LC46 problem

I've never looked for them before - perhaps digikey or mouser? I'm on my iPhone right now but will have a look when I return home (out picking up a 42" HD LCD with cracked screen for free - now missus wants to do some shopping!)

Can't beat free, nobody want's to give shit away over here.

[rmoody]

Re: LG 42LC46 problem

Well, i've fixed the power board that the customer messed up by cutting a small staple and soldered it to a trace connecting to the positive side of that capacitor. Seems to be working just fine, not the best looking thing but hey it works.