Noise-like problems on Samsung T220HD

[javitxi]

Hello to all the community,

My name is Javier and I am from Madrid (Spain), so English is my second language, then I would like to apologize in advance for any grammatical or mispelled words. Also I am at my least year of telecommunications degree specialized at electronics that maybe on Europe and USA is the same as electronic's engineer, so I think I have the background, knowledge and skills needed to try to fix the problem of this monitor (also I've done some maintenance like ~4 years ago on another electronics devices for a company).

Like a year ago my T220HD monitor started to display some noise horizontal bars at the display (hdmi, vga, dvi, YCrCb, TV, etc) on bright colours with clearly noticeable ones on whites, like the ones you can see at my gallery at photobucket:

http://s934.beta.photobucket.com/use...T220HD%20issue

(if you would require closer images or any macro of a cap, please, don't hesitate asking me because I have a much better camera right know to do so)

At the beginning, they appeared time to time and then oftenly till every time I turn on the monitor, they appeared. So, I thought that it has to be an issue with the main board, because I've inspected the power supply board without any leakage on the 'Sam Young' capacitors (as some users around the net reported but without image (black screen) or another issues). I haven't checked the voltages 'cos I wasn't sure of what values expect as an ok reading (or at least, between the margins).

Last week, 'cos we thought to get a chance into replacing the main board to fix the monitor in order to use it, I've ordered an indentical main board from SJS TV Services (one week delivery from UK to Spain, everything ok) and it arrived today. I've switched the main boards obtaining the same result.

So, I've decided to make some readings about the voltages attacking the screen (because I suppose that the ones attacking the main board were ok, the one bunch of black + 1 red cable) and I've read ~7V AC and a little offset ~200mV DC at CN304 and CN303. Also, I have the service manuals which I upload you to my dropbox in case any reader would need them (no profit or advertisement intended):

https://dl.dropbox.com/u/50215883/sa...dd_ls22tdd.rar

and I haven't managed to find the voltages or the full diagram of the power supply board in a quick first look (also 01:15am doesn't help a lot, you know). So, do you have any clues / ideas about what is happening to my t220hd (yes, it had surpassed the warranty like 2 years ago so it will be no problem replacing a component)? Maybe is it the circuits of the matrix of the LCD and I have to order a LCD replacement (which maybe is not worth)?

Thanks a lot

Javier

[tom66]

Re: Noise-like problems on Samsung T220HD

If you hadn't have mentioned that English was your second language, I wouldn't have known. It is better than many English speakers.

Regarding your problem, it looks a lot like a loose LVDS cable. This is the cable running from the main board to the LCD panel board (t-con board.) Try reseating this. Presumably you have reseated it on the main board after replacing it but have you done it on the T-con board?

[javitxi]

Re: Noise-like problems on Samsung T220HD

Hello and thanks for your response,

With the malfunctioning mainboard, I've tried to reseat the cables 1st (plug & unplug). Then after the history of the previous post, I've done the same thing. How am I sure that I am connecting the cables correctly? Well, the main board has a connector like this one (I can tell you the name in Spanish but not in English), so believe me is just imposible to go wrong putting it out and in. Also, it has another three connections: one for the current & voltage provided by the power supply (the bunch of black ones + a red one), another for the speakers and the last one for the IR (infrared, denoted as IR1, IR, Vcc and gnd as ussually on the lil' pcb) circuit.

All these connectors are showed on these pics I've just taken few minutes ago (IMG2191 and IMG2190)

http://s934.beta.photobucket.com/use..._2191.jpg.html

Any further ideas?

Many thanks for your help!

Javier

[selldoor]

Re: Noise-like problems on Samsung T220HD

Hi we do not really like pictures posted off site - there are a number of reason one is I cannot enlarge it and I can only copy by screen grab. Please post any other using Manage attachments which is found in Go advanced under the Quick Reply box.
In fact perhaps you could repost your pictures using that.

Anyway I have marked the cable Tom refers to - you need to het to where it attaches to the panel and assuming it can be unplugged , unplug, clean and re plug.

[javitxi]

Re: Noise-like problems on Samsung T220HD

Thanks for your input selldoor!

About the photos, sorry and 'll try to do that. I've just linked an external link in order you can see them at full resolution.

About the connector, yes, I've done that and the problem still remains (which is what I was referring to on my second post at this thread. Sorry if I wasn't clear). Also, I've done that with the other connectors of the main board and the power supply with the same problem (still the same).

So, do you have any other ideas? Maybe is the chocke around this cable that for any reason, had lost its magnetic properties as an isulant of RF and interference (more or less, a filter function if you know a little bit about signal processing)? I don't think so, but if the source of the signal is ok (I've ordered and put into the monitor a new main board and the problem persists), maybe the problem has to be with the other componets. I discard that the cable was deteriorated by the heat (this type of cable is in a fixed position, doesn't move and is supposed to manage the heat generated by the monitor), so the only thing after the cable is the LCD matrix.... which I am afraid something went wrong with it.

Javier

PS: Hm.... it doesn't allow me to edit mi 1st and 2nd post, so I'll try to upload over this post all the photos The photos at this post correspond to the 1st time I've dissasembled the monitor with the problem appearing everytime I turn the monitor on. I'll make another post to attach the recent photos with the new mainboard

[javitxi]

Re: Noise-like problems on Samsung T220HD

Second post with the new photos I've taken yesterday showing the position of the boards (power supply -left- and main board -right).

[selldoor]

Re: Noise-like problems on Samsung T220HD

Dose the fault always appear in the same position or is it random.
Does it appear straight away or after some time. - Trying to decide if it is a faulty panel.

[javitxi]

Re: Noise-like problems on Samsung T220HD

The position is random as it is showed on the photos with the different standard colours that power point may offer (at that time, I wasn't eager to make a vector o colours, just test why there were noise on very bright colours and white ones), no stuck pixels. As I've said on my first post, the first time these 'noise lines' appeared were for a short time and vanished. The next times appeared for a little bit more time (turning on/off the monitor did not fix the problem) and finnally, the lines appeared always on the monitor (with more heat in it -summer- with less heat -winter- for a long period of time the did not dissapeared, switching the monitor on/off several times also did not fix it, the lines were stuck were a bright colour or white appeared indepently of the video input). I've just upload also these photos I mention about power point.

So, is it a faulty panel then? As said previously, I've ever seen a faulty panel (I've own 1 LCD 4:3 for a looooong time that I quit to use when I bought T220HD). Also, I don't remember if I've mentioned it, but the problem appeared when the monitor was used for ~3 years (not always 24/7, like maybe 2-3 hours per day on).

Thanks for your inputs!

Javier

[selldoor]

Re: Noise-like problems on Samsung T220HD

Doesnt look like the panel then if the fault moves.
Does your old lcd still work?
I am now wondering about the video card in the pc. You could try taking in out, cleaning the contacts and reseating. Check the vga cable if that is what you use.
Have you tried other inputs on the monitor scart , dvi, hdmi ? I see you mention them earlier do they all produce the same problem.

[javitxi]

Re: Noise-like problems on Samsung T220HD

Doesnt look like the panel then if the fault moves.
Does your old lcd still work?
I am now wondering about the video card in the pc. You could try taking in out, cleaning the contacts and reseating. Check the vga cable if that is what you use.
Have you tried other inputs on the monitor scart , dvi, hdmi ? I see you mention them earlier do they all produce the same problem.

The first thing I've done before dissasembling for the first time the monitor T220HD was to switch my GPU (ati 5770 to a nVidia 8400GS) and the monitor presented the same problem. Then, I've disconnected all the inputs to the monitor, having only the DVI input from the Pc and the AC power cord to turn the monitor on (with just this power cord plugged to the wall). Same problem. Then I had tried disconnecting all except the power cord (obviously) to watch only TV: same problem (although on TV was lesser noticeable as on TV they are usually images in movement). Then I've tried to see a film at the Pc with the two GPUs (one each at each time) and the same problem (although there was a dynamic image, on white or bright images, they were the noise lines). Afterwards, I've tried to connect the PS2 through SCART and through YCbCR and the same problem....So yes, I've tested all the inputs in every single way trying to aisle the problem, if the problem was caused for a faulty or unsynced frame rate from the transmisor module (generator of images). My conclusion was that neither of my transmissor modules were the problem (two pcs -also I've tried my netbook through VGA- and a PS2 wouldn't be wrong generating images).

[edit] Also I've tried a new monitor (22" 16:9 LG cheapo one, my old 4:3 LCD) and also my recently buyed monitor (HP ZR2440w) and there is no problem! (as said, the problem doesn't come from the source of the image)

So, as I've said previously, my conclusion was that the main board for any reason, was faulty. Hence, I've ordered a new main board to switch it.

So, as a new main board doesn't solve the problem, I continue in the process of searching errors through the transmissor of the images (source) to the receptor of the images (destination), as the LCD is. Then, at my first post I was asking the community the voltages of the power supply (although there are no bad caps apparently -I haven't measured it's C by desoldering them (otherwise you can't tell) ), because the power supply provides energy to the LCD, mainboard and IR circuit.

Usually, if a chips tends to fail in some way, you could think it's broken but, maybe the chip isn't doing what it's designed to because of its Vcc (power voltage) which has a lot of noise, isn't enough, is to much, etc. As the two main boards are presenting the same problem (and the one I've purchaes is suppossed to be ok), the focus moves to maybe the power supply or just the circuits in charge of control the colour of the LCD panel (which I don't know if they are inside the LCD package or if you can dissasemble them by a standard way).

Hope the synthomps and the testing is cristal clear now

Thanks!!

Javier

[selldoor]

Re: Noise-like problems on Samsung T220HD

Well I dont really have anything else to suggest, you have been very thorough.
The only thing we have not looked at is the panel board - post picture of that and perhaps we can think of something else.