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toshiba lcd backlight light only ?

 
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jjcool



Joined: 04 Aug 2008
Posts: 7
Location: uk

PostPosted: Fri Jun 25, 2010 9:41 am    Post subject: toshiba lcd backlight light only ? Reply with quote

hi

i have a Toshiba 46ZV555DB set powers up and i can see the backlight lights the whole screen up ok.

fault is that the backlights are on but theres no picture or osd or anythink just backlight untill i can get lcd into normal tv analogue channels..

after some further investigation i managed to get a full picture on lcd, from trying blind with remote to switch av channels i managed to get picture to come on when tv is on normal tv av tv channels.

however soon as you switch av channels to hdmi, or scart or feeview mode, the lcd reverts back to just blank screen with backlight on, i can still hear sound on all inputs.
i have also noticed when the picture is on in the middle of screen theres thin black lines showing across mid of the screen and also there seems to be a mirror image reflected at at bottom of screen, i have attached a couple of pictures showing both faults.




has anyone come across this problem before? or any ideas what to try next.

i have tryed reflowing both main and tcon boards set still remains the same.


thankyou
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The_AntiRAM
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PostPosted: Fri Jun 25, 2010 10:05 pm    Post subject: Reply with quote

Try diagnosing power supply fo ripple or other issues.

Probabily the main is defective.

Check connectors especially LVDS.
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jjcool



Joined: 04 Aug 2008
Posts: 7
Location: uk

PostPosted: Sat Jun 26, 2010 11:51 am    Post subject: Reply with quote

would you say its the main av board fault or a t-con board fault?

thanks
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The_AntiRAM
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PostPosted: Sat Jun 26, 2010 7:41 pm    Post subject: Reply with quote

jjcool wrote:
would you say its the main av board fault or a t-con board fault?

thanks


THE MAIN.

The T-CON "doesn't faulty MIX signals like your posted pictures".

T-CON works on digital domain signals not on analog video components.
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jjcool



Joined: 04 Aug 2008
Posts: 7
Location: uk

PostPosted: Mon Jun 28, 2010 1:05 pm    Post subject: Reply with quote

oh ok i did not know that.

everyone thought it maybe a t-con fault. so are you saying the t-con plays no part in the anologue signal, and a t-con would not cause a double image as shown in pictures? as thought everythink passing through t-con.


i have connect a 2nd tv to the scart of the lcd and picture displays ok on 2nd set connect through scart socket so thought av was ok. however im not expert. do you still think av board?

i have noticed the big chip on the main av gets red hot.

however im unsure if thats normal.

heres a couple of pic,s of the chip that gets red hot.



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The_AntiRAM
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PostPosted: Tue Jun 29, 2010 8:25 pm    Post subject: Reply with quote

jjcool wrote:
oh ok i did not know that.

everyone thought it maybe a t-con fault. so are you saying the t-con plays no part in the anologue signal, and a t-con would not cause a double image as shown in pictures? as thought everythink passing through t-con.


i have connect a 2nd tv to the scart of the lcd and picture displays ok on 2nd set connect through scart socket so thought av was ok. however im not expert. do you still think av board?

i have noticed the big chip on the main av gets red hot.

however im unsure if thats normal.










1) - It seems that you don't have enough knowledge to do professional
diagnosis in electronic complex items. You're going by "intuitive"
searching. NOT good. It's at your own risk in further damaging things
until they're going to a complete faulty state.



jjcool wrote:
so are you saying the t-con plays no part in the anologue signal, and a t-con would not cause a double image as shown in pictures?


2) - I'm not saying. Technology of DSP says IT !
TFT panels doesn't aquire analog AV signals !!
They 're processed by main board via advanced DSP then
passed to T-CON for driving the TFT.

If T-CON was bad you have had seen some funny/fuzzy
pixel art instead of analog wrongly mixed signals like in
your posted photo, or even more nothing.

Correct diagnosis wil start with sistematic knowlegeable methods
not with the TRY IT method.



jjcool wrote:
i have connect a 2nd tv to the scart of the lcd and picture displays ok on 2nd set connect through scart socket so thought av was ok.


3) - That is a good first step to diagnose properly. WELL DONE !!!!
but insufficient.
You have only revealed that ANALOG outputs are in good functional
order and NOTHING MORE.
You skipped all the DSP and many other further advanced
devices.



jjcool wrote:
i have noticed the big chip on the main av gets red hot.


4) - SAYS NOTHING !

Many VLSI Modern Chips are running "HOT" and only for that the word
hot is totally wrongly used.

Knowlegde , proper tools, Service manual and instrumentation are
required here.




jjcool wrote:
however im unsure if thats normal.


5) - RIGHT !!!!!!



jjcool wrote:
however im not expert.


6) - WELL ENOUGH !

So make your choice: LIVE OR DEAD (Your Tellye).

Cheers.
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