LG37LF66 - video but no sound - not t-con not power supply

**tom66** · 10-12-2013, 04:03 PM

Re: LG37LF66 - video but no sound - not t-con not power supply

Grab a hairdryer. Start heating up stuff. When you heat something up and the problem occurs, you know where the fault is...
That fault definitely looks like a main board problem to me.

**zelig880** · 10-12-2013, 04:54 PM

Re: LG37LF66 - video but no sound - not t-con not power supply

if you can assure me that is nothing to do with the lcd panel.. i will buy the board after i sell the pieces that i have mistakely bought as they were not the issue...

**tom66** · 10-12-2013, 05:10 PM

Re: LG37LF66 - video but no sound - not t-con not power supply

How about trying the hairdryer first so you know what board is at fault? Hot air gun works too -- just keep temperature low. No guarantees from myself unless you test things.

**zelig880** · 10-12-2013, 05:30 PM

Re: LG37LF66 - video but no sound - not t-con not power supply

ok o will try.. but the main boardnia the only one left.. i have changed all the other..

**tom66** · 10-12-2013, 05:47 PM

Re: LG37LF66 - video but no sound - not t-con not power supply

Unless the boards you received were bad.

**zelig880** · 10-12-2013, 06:10 PM

Re: LG37LF66 - video but no sound - not t-con not power supply

hm... they did completely thebsome issue.. it seems strange... and i boufht them from a shop so i got warranty

**tom66** · 10-12-2013, 06:11 PM

Re: LG37LF66 - video but no sound - not t-con not power supply

Only way to be sure is to test... 99% of boards on the internet are not new, they are used from scrapped TVs (cracked screens etc.)

**zelig880** · 10-12-2013, 07:02 PM

Re: LG37LF66 - video but no sound - not t-con not power supply

well.. i will try tomorrow...

I thought it was the power supply.. tomorrow I will try again!

I really dont know what else to do after this... i cant belive that I cant even trust something that i buy from a shop... i knew it come from another tv.. but is annoying that i cant be sure that it is the right part..

will post more info tomorrow..

**tom66** · 10-12-2013, 07:04 PM

Re: LG37LF66 - video but no sound - not t-con not power supply

A good internet shop *should* specify the parts as being used/reclaimed and offer a reasonable returns policy. I'm a big fan of flattvparts & parts4me UK as they're both honest and have good returns policies. Boards from eBay are always a crapshoot -- some are good but others are bad.

**zelig880** · 10-12-2013, 07:14 PM

Re: LG37LF66 - video but no sound - not t-con not power supply

i bough them from tv part uk..

**tom66** · 10-12-2013, 07:33 PM

Re: LG37LF66 - video but no sound - not t-con not power supply

I've never had experience with them myself, but that doesn't mean they're bad.

**zelig880** · 10-15-2013, 02:12 AM

Re: LG37LF66 - video but no sound - not t-con not power supply

hei guys..
i cant find the solution to this problem yet!!!

Can anyone help me further to throubleshoot the parts?

I will give you as many details as possible.. probably you know what the issue is from this problem...

I HAVE NOTICED....

- when I switch the tv on.. there is a strange continuous sound coming from either the tcon or the mainboard ( they are very close and can t understad wich one makes the noise)

- if cold I can switch it on and off 1000 of times no problem, but when the problem start and i try to swtich it off and on again, the green light will blink forever...

- i noticed.. when i start the tv the image is not sized correctly.. ( is like slighly zoomed) but after few sec i can see a green flash on top/bottom of the tv and the image resizes itself... It happens everytime i swith the tv on!

- then the picture goes bad I can have Horizontal lines, double image, rolling image or black screen!

If it was the power supply.. should i see a short of V output when the poblem start? how can i fine the throubleshoot the problem?
PLEASE HELP..

**tom66** · 10-15-2013, 02:32 AM

Re: LG37LF66 - video but no sound - not t-con not power supply

Since the problem is time sensitive, in 99% of cases it is caused by heat (as things warm up stuff goes wrong.) Therefore, by heating up the parts one by one, you'll find exactly where the fault is coming from.

**zelig880** · 10-16-2013, 04:32 AM

Re: LG37LF66 - video but no sound - not t-con not power supply

UPDATE

I have tried what you told me last night...

I used my girlfriend hair dryer to warm up the single boards.

The reaction was not immediate but it seems that it is related to the power supply. I can say what part of it actually is foulty and I can say that is that 100% but I quite sure about it!

The very important bit.. is that I have noticed something that may probably confirm my thought. When the picture goes away ( because If i use the hair Dryer the image doesn't get distorted, it just disappear completely!)

Anyway, going back to my very important bit, When the screen goes away the bottom of the power board, ticks multiple time.. I have tried to understand where the tiocking comes from, but it seems like it come from the yellow think ( i dont know the name) named sj0733.

Another important point. If the tv is warm and the image is gone ( the image doesnt have to be gone..) the TV power off button doesnt work!!! not on the remote and not on the tv!! even if i keep it pressed it wont work... but if the tv is cold it works perfectly..

power supply image

Another point, if the image is gone and I put some fresh air on that part of the board, it ticks, and for every tick the screen flicker white ( like if it tried to show the image but can manage to do that!)...

So... What is that yeallow bit.. can I assume is the power supply that fails of it can still be something else that make that bit click?!

thank you for your help!

**tom66** · 10-16-2013, 04:38 AM

Re: LG37LF66 - video but no sound - not t-con not power supply

Well that is possible but to me it seems unlikely. That part is the PFC coil which is part of the PFC circuit. It might make a ticking sound when the TV is in standby. Did you try parts of the main board too?

**zelig880** · 10-16-2013, 05:08 AM

Re: LG37LF66 - video but no sound - not t-con not power supply

I tried to use the hair dried on every board...

I never experienced anything when i was blowing on main board or tcon or inverter, but the image disappeared when i blowed on the pwoer supply..

Bear in mind that it was not immediate.. i had to blow for minutes to let the image go!

If the image is distorted the ticking is continuous.. then when the image disappear the ticking stops and it just happen randomly ( and when this tick happen i can see a change of luminosity fromk the back of the backlight).

Where shall i focus.. should I see a drop of voltage output when the the image goes away ( if it is a power supply problem)...

**tom66** · 10-16-2013, 05:29 AM

Re: LG37LF66 - video but no sound - not t-con not power supply

Yes, I'd expect the outputs of the power supply to drop if that were the case -- try checking those before it flickers, while it flickers and when it goes blank.

**lanada** · 10-16-2013, 05:58 AM

Re: LG37LF66 - video but no sound - not t-con not power supply

check power supply for heat issue

**zelig880** · 10-17-2013, 09:25 AM

Re: LG37LF66 - video but no sound - not t-con not power supply

Well.. todays update...

I have checked the TV voltage before during and after and they are completely the some....

Nothing changes. even if the transformer clicks when the image disappear the voltage are always the some..

I have also noticed that If I take off the power cable every time I use it.. it last quite a while.. last night ( with the back open) it lasted over 2 hours.. and actually didn't go off at all.. i went to bed! lol but it was a cold night and the back was exposed..

Can i just make a small questions.. i got two small plastic buttons on the main board.. what are they? ( is just curiosity i dont expect to fix the problem with them..)

LG37LF66 - video but no sound - not t-con not power supply

LG37LF66 - video but no sound - not t-con not power supply

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