LCD Screen problems

[friscokid]

I have an emprex LCD tv that is having problems. Started with just a couple of vertical lines going out, then intermittent whole bars would go in and out, now the whole half of the screen is a weird pattern.



Any idea's what this might be? I haven't opened it up yet, but searching to web, I'm confused whether it might just be bad caps, or inverter board or CCFL's...

Any suggestions welcome.. I'll be opening it up tonight.

Thanks! Mike

[PlainBill]

Re: LCD Screen problems

I have an emprex LCD tv that is having problems. Started with just a couple of vertical lines going out, then intermittent whole bars would go in and out, now the whole half of the screen is a weird pattern.

Any idea's what this might be? I haven't opened it up yet, but searching to web, I'm confused whether it might just be bad caps, or inverter board or CCFL's...

Any suggestions welcome.. I'll be opening it up tonight.

Thanks! Mike

Remember 'Brewster's Millions', where Richard Pryor ran for election as 'None of the above'? The cause of your problem is probably none of the above. It's probably bad drivers on the panel, but might be a bad main board. It's certainly not caps, inverter or CCFLs.

PlainBill

[friscokid]

Re: LCD Screen problems

If I open it up, is there are way I can measure something to tell which is wrong.. I only have a DMM.
Assuming I can order these parts myself? It was a cheap TV a few years back, so I don't know if I'll be able to get parts or not.

Thanks, Mike

P.S. I've had 4 major electronics go bad in 2 weeks... spooky.

[Wizard]

Re: LCD Screen problems

There are not much you can do to diagnose, either T-CON (the small board between
mainboard and the actual LCD itself (covered by screwed down steel cover).

Either T-CON is bad or LCD itself. tap and flex with back off, avoid the power supply board, work with one hand.

Cheers, Wizard

[tmwalsh]

Re: LCD Screen problems

From the appearance, it looks as if the 'last half' of the scan is losing its horizontal component. Either the 'next column' address is not being sent, or the 'next column' has bad componentry that makes it unable to light up the 'dots'.
Each spot on the screen has a H address and a V address.[for each 'point' of the color triad] If all three light up, you get white.
That said, the right half is not getting the signal to light up a LOT of columns, meaning the Horizontal address is not there, or the columns are not responding -- for all 3 colors.
I would look at the ribbon from the main board to the lcd display. Make sure it is tight in the socket. Maybe even remove/replace to exercise the contacts. What do you have to lose? It could even be a memory chip where the 'screen' is buffered for each frame, 30 times a second.
tom

[Wizard]

Re: LCD Screen problems

Not on these LCDs.

X address lines (vertical lines) is number of driver ICs on circuit tapes, both ends are thermal bonded to the two or three bus circuit boards (narrow, long circuit boards with simple components, no ICs) depending on long length of LCD. From these circuit boards goes to T-CON board. Much of the LCDs had internal wiring that goes from one of long board circuit inside the LCD to the Y line driver boards. That T-CON is what you see and is connected via LVDS cable to the mainboard.

Can be bad line drivers ICs, bad T-CON. Mainboard does not exhibit this flaw.
If there is a bad connection via LVDS or between T-CON and long boards internal to the LCD (via ribbons) is pinstripes across WHOLE screen. Sometimes can be in the T-CON board.

This is reason need to diagnose. T-CON means Timing Control board.

Cheers, Wizard

[friscokid]

Re: LCD Screen problems

Finally got back to the TV. I was able to find an exact match for the TCon on ebay for $40 so I ordered it and hoping it fixes my problem.

However, I noticed on the signal processing board, there are 2 bulging caps.
One is labeled Misuda 1000uf 16v. I can't find anything about this cap.
I'm assuming I can replace it with any relatively low ESR cap? I have a bunch of extra's from a previous order for a motherboard.

Thanks, MIke

[Wizard]

Re: LCD Screen problems

Perfect. do that.

Cheers, Wizard

[friscokid]

Re: LCD Screen problems

Bummer, replaced the T-Con board, and TV has exact same problem.

The only other component between T-Con and LCD screen is Hitachi Inverter board. I'm guessing this is where the 'bad line drivers' would be located?
I can buy a replacement inverter board for $40, but I just dumped $40 on the T-Con board, and I'm just guessing here.
At this point, I'm tempted to just replace the whole thing.

Anybody have an opinion on this one?

Thanks, Mike

[PlainBill]

Re: LCD Screen problems

Bummer, replaced the T-Con board, and TV has exact same problem.

The only other component between T-Con and LCD screen is Hitachi Inverter board. I'm guessing this is where the 'bad line drivers' would be located?
I can buy a replacement inverter board for $40, but I just dumped $40 on the T-Con board, and I'm just guessing here.
At this point, I'm tempted to just replace the whole thing.

Anybody have an opinion on this one?

Thanks, Mike

I have several, in order of confidence.

#1 - Listen to wizard.

#2 - The inverter provides high voltage AC for the CCFLs. I doubt that is the problem.

#3 - I believe the drivers are located on the panel circuit board - part of the LCD panel itself.

PlainBill

[Wizard]

Re: LCD Screen problems

Inverter supply are for lamps to light up the panel.

The vertical lines IC drivers failed. They are bonded to the panel itself via tape circuits.
Have two options, replace whole panel or send the panel to a panel repair shop (find one via google).

(FYI: I work with LCDs often to know this.)

PS: T-con is worth keeping for someone who need it or yours if your panel's T-CON fails later if you choose to replace exact panel or have panel repaired.

Cheers, Wizard

[friscokid]

Re: LCD Screen problems

I did a couple of google searches. I found one company that listed flat rate repairs for LCD at $350 for a 32" TV. This is exactly my replacement cost for the 'cheap' TV that it is. Actually, I've seen a toshiba on newegg for that, which is probably better than my shitty emprex from Frys.

Everything I've seen so far, seems to say that these repairs are beyond a DIY.

It looks like economically, I should just buy a new one. I couldn't find anywhere that actually sold LCD panels. Would I have to buy that for my specific TV? I wouldn't think they are interchangeable...

Cheers, Mike

[Wizard]

Re: LCD Screen problems

there are so many models that uses same LCD panel if you look and search around.
But this unit you had served you well and it is time to invest in good brand this time around especially major brand. This means paying bit more. Like 500-1,000.

And better take a look at LED backlight LCD TV, Few brands do exist for 32" using LED backlight. The CCFL is not very good on power usage vs CRT. 180-200W for CCFL backlight for 32" vs sub 120W for LED backlight 32" and some did measure the actual draw and saw around 70-80 which is rather excellent.

LED backlight just came this very recently was one of two reasons I did not buy big LCD for so long. The other reason was scaling of SD input regardless of signal quality is simply awful. First reason was mercury found in all arc bulb lightings (includes fluorsecent, CCFL, HID as well) and plamsa panels.

Cheers, Wizard