Toshiba 42WLT66 - Mura on screen

[tom66]

I know mura isn't usually repairable but I've got a strange one:

Bought it off these guys for £50 and that included a glass AV stand, the remote control and a manual. So, not bad - the stand alone sells for around £150.

The black levels have a slight amount of unevenness, the grey is a bit worse, and normal watching is perfectly fine, barely noticeable.

It's an older LCD but full HD. Motion is a bit blurry here and there - pretty typical for older LCD panels. Colour was set way oversaturated, so I tweaked that and it looks better now.

I'm also going to take off the cover - JUST to have a look inside - no repair is really needed. I will post if I am impressed or upset. Newer small Toshibas were at one point Vestel sets, which is highly disappointing for a good name brand like Toshiba, but it might be different for their big screens.

The people I bought it off said they got a new 3D LED TV, so maybe it was just an excuse to get a new TV?!

[tom66]

Re: Toshiba 42WLT66 - Mura on screen

Interesting... I'm not sure if it's just me, but I laid down the TV for a couple days and the mura is mostly gone?! There's a tiny bit just about visible if you look at the screen at just the right angle (both horizontal and vertical.) Placebo effect?!

Anyway, teardown analysis:
- Design uses good caps in most places except parts of the secondary DC-DC board, which uses a few Jamicon, but otherwise fine. And Jamicon are probably okay general purpose caps.
- Main reason for mura is use of a CMO LCD panel, which is common with those types of LCD panel. Also has hideous motion blur (quite noticeable, probably one of the worst I've seen from an LCD so far. I didn't notice it so much initially - I thought it was the digital noise reduction feature - but it's much more prominent now I look closely at it.) An LG-Phillips LCD from the same era does not experience such motion blur, so I expect it's just because they used a bargain basement LCD.
- Three supplies: One for 24V, one for main voltages and one for standby. Huge primary capacitance of 270uF.
- Use of a hybrid module for the 24V instead of discrete devices. Repair will be difficult if this part fails.
- Main board has some crappy caps on it and a bodge or two in places.

For a £1,600 TV I give it 7/10. Better than most...

[Scenic]

Re: Toshiba 42WLT66 - Mura on screen

What do you mean with "mura"?
Moiré (the wavy stuff like here and here) ?!

[tom66]

Re: Toshiba 42WLT66 - Mura on screen

What do you mean with "mura"?
Moiré (the wavy stuff like here and here) ?!

This is a bad case of mura: http://guide2lcdtv.com/wp-content/up...ngsharpsv7.jpg

Mine was worse than that and it was more dark than lighter patches.

This a good case of mura (pretty typical for most budget LCDs): http://i30.photobucket.com/albums/c3...14/mura002.jpg

Some info on the problem regarding Sony (who manufacture LCD panels with Samsung): http://www.hdtvtest.co.uk/news/sony-...2007033142.htm

Mura: Japanese for unevenness.

A lot of people on forums suggest loosening case screws may fix the problem... well I did disassemble it and reassemble it... which may have been the fix. That's lucky , I didn't even think about that being a fix.

[Scenic]

Re: Toshiba 42WLT66 - Mura on screen

oh.. clouding & banding.. well that explains it
Haven't heard of the term "mura" before. That's why I was a bit confused..

Loosening the case screws makes sense. I've had a cheapo LCD monitor with really bad banding (both sides much brighter than the center) which was caused by the panel literally being slightly bent by waaay too tight screws holding the panel in the frame.

edit: looked kinda like this, just a lot worse click
On a fully black screen, the both sides were sort of blue-ish gray, with the center being almost pitch black