Magnavox 42mf531d Shadows on screen

[allsmith]

My friend bought two of the same model used tv's not working.
Manufactured september 06
Both tv's had vented caps on the PSU,he only replaced 4 caps on each tv,and that made the tv's work.
But both tv's have these shadows or blochyness on the screens,pic is of the better of the two.
Both tv's seem to be working fine except the shadows,I have been watching this tv now for about 3 weeks and its on about 5 hrs every night.
Its noticable watching tv but not really too bad, its better or worse depending on what color is on the screen,I hooked it up to a laptop to get just one color for the pic,it really stands out with like gray or blue backgrounds,but not as bad with white or black.
Any ideas on what could be causing this?
I open it back up to look at the caps on the main board,since we didnt look the first time we worked on it,there is only 3 electrolytics that i can see on it.
This thing looks like it would be a pain to trouble shoot because of how its designed on the back! The mainboard and psu are in one enclosure and nothing is accessible unless you disconnect everthing and pull the enclosure.
Could this be a bad panel,or T-con board?
Any help would be appreciated!
Thanks,Lonny

[drpj23]

Re: Magnavox 42mf531d Shadows on screen

What's the other TV's shadow look like?

I would go down to the CCFL tubes behind the LCD and see if there is not anything hanging. Inspect the LCD (very carefully) and diffusers (white sheets).

[allsmith]

Re: Magnavox 42mf531d Shadows on screen

What's the other TV's shadow look like?

I would go down to the CCFL tubes behind the LCD and see if there is not anything hanging. Inspect the LCD (very carefully) and diffusers (white sheets).

I dont have a picture of the other set right now,but will see if my friend will send me one.

The other tv is worse looking than this one,but its not the same pattern.

I have never had one apart down to the lamps yet,but would like to see what inside these things.

Any tips so i dont damage anything?

Thanks,i'll try and get a picture of the other tv as soon as i can.

[kc8adu]

Re: Magnavox 42mf531d Shadows on screen

bruised panel.
it took a hit.
dont waste your time trying to correct this.only fix is a new panel.

[drpj23]

Re: Magnavox 42mf531d Shadows on screen

Well that makes sense lol.....Ive actually never seen that on a tv though I see that happen to like TI-83 and 84s all the time. If it got bumped, then it got damaged enough to do that but not crack.

Well now you can see what's inside them without worry

[tom66]

Re: Magnavox 42mf531d Shadows on screen

To me it looks more like mura, due to poor design of the panel it has been damaged due to heat. It too is unrepairable. Very, very common on CMO and Chungwha panels.

[allsmith]

Re: Magnavox 42mf531d Shadows on screen

To me it looks more like mura, due to poor design of the panel it has been damaged due to heat. It too is unrepairable. Very, very common on CMO and Chungwha panels.

My first fear was we damaged the screens by how we were handling the tv's and how we layed them down to work on them,but we where very careful.

Do you think the heat damage comes from the lamps or from the psu or mainboard? They sure added a lot of extra heat sinks and compound on the top of mainboard and to the top of the psu.

It looks to me that the psu is directly behind the worst part of the shadow.


Do you think the heat damage occurred when the caps failed on the PSU?

Just wondering if the damage was there before the caps let go or not.

Thanks

[tom66]

Re: Magnavox 42mf531d Shadows on screen

I believe (though I'm not certain) it's due to the internal layers of the LCD de-laminating, and the heat from the bulbs is the likely #1 cause, next to heat from other boards. I doubt bad caps caused it.