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Author Topic: Reasons a monitor won't turn on.  (Read 7808 times)
harberst
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« on: June 11, 2011, 04:40:54 AM »

So in my attempt at making my own DIY cintiq I may have, kinda, most definitely, snapped one of the tube light/back light things. It still turned on and had a nice picture so I didn't think much of it and finished up, but now the monitor is not turning on.  Could this be because of the broken tube or did I manage to foul up something else?
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bernard
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« Reply #1 on: June 11, 2011, 03:19:11 PM »

well you said it worked with the broken  tube. it must be something else then.  Check all the connections, push at various area to see if anything happens -- do you hear any subtle sound while powering up?  If you can dismantle the LCD, you might try to send a lot of light through it to see if it is only the backlight the problem or the lcd matrix.

not much else I can tell you at this point -- take a few pictures to show us!
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harberst
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« Reply #2 on: June 12, 2011, 04:18:06 PM »

I found the issue, one of the wires snapped right at the connection.
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harberst
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« Reply #3 on: June 20, 2011, 08:47:07 PM »

Alrighty, fixed that issue with a bit of soldering, got it assembled. Worked okay, except oh ye gads the jitter! Which, to be fair I was aware was a potential issue (internal power source, hey it was a free monitor nothing else but to try it out right?) So I took it apart again to see if I couldn't move the power source elsewhere. 

Long story short (too late!) I don't have a picture now. As far as I can tell there are no loose or snapped wires, everything (should) is plugged in it's proper place. There is no sound when the monitor powers up, but it does power up. And then all is darkness, well on the screen anyway.

Have some pictures: (I'd say sorry about the size, but when it comes to this stuff it's better to have it large enough to see some detail)


Power light's on, ignore the duck tape residue on the cover.


Black splotches at the top when it comes on.


Wires.


Power source
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bernard
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« Reply #4 on: June 20, 2011, 09:28:23 PM »

one missing thing is the grounding -- because you unscrewed the boards, you lost some of the grounding connection. Sometimes they are important, especially because of the high-voltage of the backlight on some monitors. I had an issue once because of that (it was an IPS monitor with 6 CCFL lamps). If you can, find a bit of wire and try to connect the boards (and the LCD Panel metal "case" in particular).  It might not work still, but it's a try.

Maybe try it but without the backlight -- or with only one of the two CCFL at a time (I see you have two).   Beware to always power down everything before even approaching the CCFL inverter and connection -- these can spark even if you do not touch it (just by being close to a contact -- I am talking millimeters of course).  Doing this will bring the mAmp down and will see if the problem has to do with the supply.

"then all is darkness" -- did you mean that you saw an image appearing for a split second -- like a logo or anything?  

So the screen is dark but the backlights stay ON?

With the VGA cable disconnected, can you get to the OSD menu?  

Is there a LED that would indicate a special condition? What do you think this led is trying to say? Like flashing, yellow, not lit or red?

Are you sure the signal sent through the VGA is "OK"?  Not too high in frequency? You should stick to 60Hz. If this was once connected to a CRT it maybe have been set to 75Hz/85Hz (popular frequencies) and/or for resolutions not matching your LCD.

If you are with Windows, try to run Entek PowerStrip while the VGA is connected and monitor powered up. Maybe there is something to do in there(?)
« Last Edit: June 20, 2011, 09:33:22 PM by bernard » Logged
harberst
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« Reply #5 on: June 20, 2011, 10:16:58 PM »

Thank you for responding. I really appreciate your help. 

Upon reassembly (I forgot rule 1! If it breaks after you take it apart put it back together!).  I hear a buzzy/whirry/ type of noise and get a single blue line across the middle of the screen (horizontal) and parallel blue and green lines vertically across the left edge.

In regards to the other suggestions

Quote
. . . with only one of the two CCFL
Actually that picture's deceptive, I learned how fragile those are really early in my build so there's actually only one functioning one.


Quote
"then all is darkness" -- did you mean that you saw an image appearing for a split second -- like a logo or anything? 
Yes actually, it appeared that my desktop icon flashed on for a sec before it went blank.
 
Quote
So the screen is dark but the backlights stay ON?
No, the only thing that stayed on was the green power light.


Quote
Are you sure the signal sent through the VGA is "OK"?  Not too high in frequency? You should stick to 60Hz. If this was once connected to a CRT it maybe have been set to 75Hz/85Hz (popular frequencies) and/or for resolutions not matching your LCD.
I haven't changed any settings on my netbook since the last time I checked the monitor (when it still worked).
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bernard
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« Reply #6 on: June 20, 2011, 11:03:15 PM »

Quote
there's actually only one functioning one.

Disconnect it if non functioning.

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Yes actually, it appeared that my desktop icon flashed on for a sec before it went blank.

Not clear: Are you saying an image appears each time you power it on?

If the backlight is OFF, you would not see those lines.

Really I am not following. I will ask the questions and we will try to explain this more carefully:

#1- When exactly do you see the lines
#2- when do you see nothing
#3- when is the backlight ON vs. OFF
#4- when do you see your "desktop icons"?
#5- Is it possible to bring up the monitor OSD menu?

it may be strange questions, but it (may) help pinpointing the issue.  
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harberst
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« Reply #7 on: June 20, 2011, 11:16:39 PM »

Sorry about any lack of clarity.  My ability to express myself has an inverse relationship to the amount of frustration I'm feeling.

There were two different instances one while everything was disassembled. And one when I reassembled it.

The lines (and noise) occurred after I reattached the power supply to the metal backing. 

The image was while it was still completely disassembled. This was also when everything (except the power light) shut off.

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#1- When exactly do you see the lines
After reassembly, upon start up.

Quote
#2- when do you see nothing
while "disassembled" shortly after start up

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#3- when is the backlight ON vs. OFF
It stays on now that the power supply is reattached to the back, but when it was loose it turned off.

 
Quote
#4- when do you see your "desktop icons"?

It was a very brief flash when I had the power supply unattached to the case.

Quote
#5- Is it possible to bring up the monitor OSD menu?
No, but it hasn't had a menu since. . . well, I'm not sure.
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bernard
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« Reply #8 on: June 21, 2011, 01:50:32 AM »

lol Smiley  I understand this is super frustrating, I would not be very happy myself.

Ah, so by "reassembly" you mean the boards are screwed together.

So that brief flash of seeing an image is no longer happening, right?  Not a single trace of an image anymore (other than those weird lines)? 

Have you tried without the VGA connection? 

If you tried pressing any OSD menu button, any flickering happening to the lines?

Try to "press" and "gently jiggle" all the connections while powered up (there are a lot of fragile connections on the side of the LCD Matrix).

You disconnected the broken CCFL, right? I do not want a short in there (or maybe you removed the CCFL lamp completely?)
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harberst
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« Reply #9 on: June 21, 2011, 02:15:15 AM »

Upon removing the CCFL I no longer get lines or noise on start up.  I think the picture flash was a one time thing  because that's not happening anymore.  Playing with the menu buttons (sometimes) causes the backlight to flicker on. Removing (or adding) the VGA cable results in no change. None of the connections cause any change.  I do not get any sort of visible menu. 
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bernard
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« Reply #10 on: June 21, 2011, 03:04:35 AM »

OK -- that changes every post! I think your LCD is alive !!   Grin

Quote
Upon removing the CCFL I no longer get lines or noise on start up. 

That was the *broken* CCFL, right?  I mean you still have the good one CCFL connected?

If the backlight is OFF, you will see absolutely nothing on the screen -- even if your desktop is showing the most flamboyant desktop picture.  Well, that is unless you have a way to shoot a strong light through the LCD matrix (which is often difficult due to the fact that the backlight plastic slab is typically opaque).

Some have dismantled the LCD Panel completely (watch out the order of all the sheets in there) and then you can see the image (if there is one -- like the OSD for instance) with some light going through. 

If your problem is only the backlight, then you are in good shape (because it is far easier to fix).  Of course doing this is a very delicate operation. Watch out for dust -- keep the parts clean if you can.
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harberst
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« Reply #11 on: June 21, 2011, 03:25:13 AM »

I tried shining a flashlight through the layers, but all that got me was seeing a dim flashlight spot on the screen.  

I meant that the picture doesn't flash up anymore, when the backlight comes on the screen stays black.  I'm about half tempted to start looking into controller panels. Or at least pull apart more of my old laptop. It had a samsung lt133x1-104 lcd panel.  I'd rather fix this one if possible (I lack the funds for a controller kit).  

Addendum: Yes it was the broken one I pulled.
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bernard
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« Reply #12 on: June 21, 2011, 03:55:32 AM »

your old laptop: "had" a samsung lt133x1-104 -- you mean it is gone?  Because other than the inverter circuit, you typically cannot find a "monitor kit" controller in a laptop circuitry.  Only a the LCD Panel.

OK -- are you saying now that the backlight *stays up* (not just for a second)?

If the answer is "NO, the backlight does not stay on very long", then disconnect the backlight and try with your flashlight in case you see something -- try bringing up the OSD menu as well.

If the answer is "YES, the backlight stays on but still the image stays black", then disconnect the VGA cable and try bringing the OSD menu. This is either a chip burnt on the controller or a misconnection (I know you checked all already).  Not much to do without more special tools.

I just did a lookup of that samsung panel, I am not sure if there is a typo, but I see 3 bits per "pixel" (for a whopping total of 8 colors??) normally it is 6bits/channel (256K colors) or 8bits/channel (24Millions colors).  It's a typo OR it is really, really old.
Resolution: 1024 x 768 Panel Voltage range: 5 volts
Type: 13.3” XGA TFT Pixel/SHFCLK: 2
Pixel Depth: 3 bits/pixel Interface: 18+18 Dual channel 5V LVDS
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harberst
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« Reply #13 on: June 21, 2011, 04:04:38 AM »

It's really, really old. Let's see my Aunt had it before she gave it to me and that was over five years ago. . . Hmm, maybe using that thing isn't going to be a workable solution anyway.

Well then back to the task at hand! The answer to the backlight is "no it does not stay on very long." And I'm not sure how to pull up the OSD menu. I haven't been able to pull up the menu since I started the build.  Anymore testing is going to have to wait until morning, as it's getting rather late here.  Thank you again for your help. 
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bernard
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« Reply #14 on: June 21, 2011, 04:45:46 AM »

It is remotely possible that the circuitry is detecting the missing lamp/invalid voltage and decides to simply shut off. In the cases I have seen it was independent, but I think some have reported that behavior.

I would think that the shut off (if happening) would also do something to the led -- do you think the led does something at the moment the CCFL shuts off? -- I see 2 green leds in there -- do you know what are they for?

OK, you do not know how to make the OSD menu appear. What is the original monitor model exactly?

One thing to try is to disconnect all the CCFL lamps and use the flash light to see if the VGA image ever appear. (Also carefully watch the led(s) to see if there is any difference with the above).

We are trying to pinpoint the culprit(s). A LCD Panel is divided in a few areas and sometimes you can deduce that one thing is working vs. the other.
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