Hi I am having problems with a NEC tv 23" lcd. There are two vertical lines about an inch wide that form together to make one (sometimes). These lines are on the right side of the screen looking at it. they seem to appear and disappear. appearing mostly as pinkish lines but not always visible. Is this something that can be caused by bad Caps? Is it something that will get worse? A problem that is very difficult to describe because it appears intermittent. I have emailed the manufacturer but no response. Any help greatly appreciated.
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Re: NEC TV with vertical lines
LCD panel.
Got warranty?
Cheers, Wizard -
Re: NEC TV with vertical lines
@ davg: if these thick lines appear always in the same place, I think there are two possible reasons: the first pixels in the columns are struct or two of the silicone contacts (aka "zebra stripes") on the vertical control are either moved from their default position or defective. For the first case switch off the screen and press gently on it near the upper part of the frame where the thick lines are; if it doesn't solve the issue, then these contacts are bad. Silicone contacts can be a pain: if their position is changed by a fraction of millimeter, then this prevents signals (in you case, the vertical control ones) to reach the lcd matrix; this issue happens when the screen gets a big shock (e.g. fall from a table) or due to heat (bad dissipation).
If the screen is still covered by warranty, then call the manifacturer for a RMA; if it isn't and you're both patient and brave and own a microscope, then open the lcd, locate the silicone contacts on the top, remove the two bad ones, clean both them and the tracks on lcd with isopropyl alcohol, lastly reseat the rubbers with the aid of the microscope. No kidding: a magnifying lens wouldn't be strong enough to see the end of silicone contacts and a bad reseating could kill your screen.
ZandraxHave an happy life.Comment
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Re: NEC TV with vertical lines
Old days of zebra strip is over when density of lines got real tight. The connecting tape is thermal bonded to the LCD glass substrance conductive lines with pressure and heat or ultrasonic.
Oh yeah, the tape have bare flipchips for each column bands and there are more for the horizontal bands. The circuit board that is connected to these flex wirings are merely just bus lines connecting them all to a voltage and few ICs.
This is panel exchange only where repair is not possible for most except at LCD repair factility.
Cheers, WizardComment
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Re: NEC TV with vertical lines
Thanks Wizard.
So if the screen is out of warranty davg can't repair it by himself but only turn to a repair facility
ZandraxHave an happy life.Comment
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Re: NEC TV with vertical lines
Got the pics of what current panels are constructed.
Give me few to post them.
Cheers, WizardComment
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Re: NEC TV with vertical lines
Reason I am posting these to give others a good understanding of this typical LCD that is currently in market is like this. Also plamsa panels are done same way but tape end to the circuit boards are disconnectable. All the tapes have a IC dies bonded to the tape pads via ball interconnects.
Here's pictures:
Whole LCD, note that you are viewing LCD from back in all these.. All the circuit tapes are thermal-bonded to glass substrane.
Horizontal line driver IC in detail, note the bus lines are both on tape and small area of LCD's edge that interconnect all 4 ICs from the circuit board in series.
Vertical line driver ICs unfolded out: Note the circuit board to tape area is soldered using silkscreening process to lay down solder paste then heated in place. But the tape to glass is different as I described above.
Folded up as designed when assembled in a panel assy:
Cheers, WizardComment
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Re: NEC TV with vertical lines
More trivia:
This particlar LCD is 1280x1024 each line is for r-g-b subpixel so one of IC in vertical driver is probably (number crunching) 1280x3 then divide by number of vertical IC driver to get lines per V. IC is 480 lines per IC!
Horizontal IC drivers is only to drive row address so I simply divide 1024 by 4 is 256 lines per H. IC driver. But there could be much, more lines and I'm not totally clear on the what circuit is constructed this way.
But I know for SURE is that all matrix panels designs are exactly laid out like memory addressing in coumns and rows. The controller sends out a info on how bright the red, green or blue by one string of 0 and 1's and is encoded in same string to address exact subpixel. All this is transmitted by LVDS from video controller on mainboard at HIGH speed, ultralow voltage (around .2V swing via differential signaling (hence the twisted pairs) or so around 50mhz or more).
Draunting eh?
Cheers, WizardLast edited by Wizard; 12-08-2008, 09:05 PM.Comment
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Re: NEC TV with vertical lines
Damn the 10 min editing time:
More on panel stuff:
But I know for SURE is that all matrix panels designs are exactly laid out like memory addressing in coumns and rows. The controller sends out a info on how bright the red, green or blue by one string of 0 and 1's and is encoded in same string to address exact subpixel. All this is transmitted by LVDS from video controller on mainboard at HIGH speed, ultralow voltage (around .2V swing via differential signaling (hence the twisted pairs) or so around 50mhz or more).
Same with DLP IC except flip a mirror one way or other and how fast or slow to reflect less or more of light per amount of time (vibrating) for light intensity to do one color at a time and have to do all pixels in turn for one whole picture in each color and color wheel have 6 segments (red, green, blue, repeat) spinning at 9,000rpm.
Plasma is very, excrotic in how a cell is driven. Way very complex to do and do it very fast despite the high capacitance loading lines and at 90, 190 and minus voltage of around 70 rapidly. It has to discharge a charge in the cell, prime it to pre-fire voltage and spike it with a fire to get it to pop alight then lower voltage to keep current low and not to burn out drivers/cells due to neon gases discharge is negative resistance when in excited stage so it needs surtain current/voltage, giving the sharp pulses and capanacitance discharge curves imposes huge load on the drivers. This wild dance of pulses causes the drivers to emit lot of heat and panel itself as well. That's the REASON the wattage is very high for plasma (over 400W for a given 42" size or so, vs LCD at around 240Wish where most of it is in lamps and some in mainboard processing while panel itself only consume less than an amp or two at 5V.
That is where big push is on for SED, OLED, LED lighting in back light and LED DLP will give you BIGGEST power savings for GIVEN size. And as a consumer you are also responsible to damand the same from makers. And LED does not contain mercury where DLP lamp, LCD backlight lamp cold cathode types and Plasma contains mercury.
Oh yeah, ask samsung why quit the 46 and 50, 56" LED DLP and no small LED-LCD panels in 20, 24, 27, 32, 40, 46 and 50 and also 60"? They only offer LED LCD in one size 70" which is way too large and rather small market share. Here why I'm asking that. And majority of people buy 27", 32" and 40" as most common sizes, and some in 50" size, that's where money are in these sizes. Also I wanted LED LCD or OLED or LED panel for monitor in 20-24" size.
PS: 50" LED DLP by samsung is 230W while a regular 50" LCD is around 250-280W, 50" Plasma is around staggeringly high 500Wish.
Cheers, WizardLast edited by Wizard; 12-08-2008, 09:27 PM.Comment
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Re: NEC TV with vertical lines
Wizard, you're a panel bible.
Basically, on davg screen the two rightmost vertical contacts don't work correctly: the control chips may be damaged or the tape bondings weak.
About energy savings: LCD screens are already a big improvement over CRTs (a 22" LCD and a 15" CRT draw about 50 W each), LED backlight could help to reduce consumption even more if you use expensive high luminance (or super/ultra/maxi/iper/whatever-the-marketing-division-chooses-after-a-booze high) LEDs.
SED is an interesting technology (1 micro CRT per pixel, it should retain both advantages of CRT and reduce most disadvantages such as convergence issue) but there are only a few prototypes from Canon and Toshiba: it's like the Holographic Disc, great potential but (maybe) available only in a distant future; OLEDs must solve some reliability issue (short lifespan) before their official launch; DLPs are good only for big tv screens, not for personal monitors.
ZandraxHave an happy life.Comment
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Re: NEC TV with vertical lines
Issue is the watts goes up badly around 20"-24" mark for LCD wattage.
Meaning, you don't get efficent one with lamps in LCD panels in 27" and up, unless going all LED at this point.
I fixed many 61" RCA rear proj CRTs chassis (ITC222, around 2001-2005ish) and they only consume 230-240W. Nobody else can touch that efficientcy at that size yet.
Cheers, WizardComment
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Re: NEC TV with vertical lines
This is way out of my league. I guess I will leave it as is since it is not too too bad. These lines only appear on some screens and therefore not that annoying if it do not get any worse. I have not opened the thing up so I have no idea as to what goes on inside. But can I expect this to get worse?Comment
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Re: NEC TV with vertical lines
Hi again I know this is an old thread but this problem seem to be getting a little worse. I have attached a picture in hopes it gives a better understanding of the problem. Is this an lcd panel problem or could it be something else?Attached FilesComment
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Re: NEC TV with vertical lines
That's a band, not line.
One X driver IC failed. Send the panel out for repair (yes there are LCD industry repair) or replace to tune of over a 500 dollars.
Cheers, WizardComment
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Re: NEC TV with vertical lines
Thanks Wizard glad I posted a picture. I guess I should open the thing up. Is replacing a failed x driver IC something I could tackle? if so where would it be located? I have repaired a number LCD monitors but no experience with TV's
Thanks davgComment
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Re: NEC TV with vertical lines
I've manage to 'repair' monitors with similar faults by wedging a piece of paper in between the case and the faulty edge connector - just enough to hold the flex to the glass, but identifying where the fault is involves gently flexing the flex cables with the driver chips on until you figure out which one is faulty (its not always obvious), and that obviously carries the risk of making the problem many times worse.
A 'proper' repair is not something you can do at home (unless you have one of these http://www.pixel-interconnect.com/examples3.html in your garage), but if you've got nothing to lose its worth a try.Comment
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Re: NEC TV with vertical lines
Thanks Harvey I have not opened the thing up yet which I plan on doing. I will give particular attention to your method and hope for the best. Will post later as things unfold.Comment
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Re: NEC TV with vertical lines
Be extra careful.
Not easy to do because the driver ICs are on the tape bonded to the LCD, easy to tear.
and is hidden by the metal frame that hold LCD to the LCD panel chassis.
Think hard on getting a quote from LCD repair factilty first.
Cheers, WizardComment
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Re: NEC TV with vertical lines
Thanks Wizard well do not sure where to find a repair facility in eastern Canada that would have the equipment to do such repairs?Originally posted by WizardComment
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Re: NEC TV with vertical lines
Google.
Good ones usually should tell you how to pack the panel or send you package to ship panel in it.
Cheers, WizardComment
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