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Old 05-28-2014, 06:57 PM   #21
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Default Re: Dell 2007WPF Flickering Off

"It's been fine for past 5 hours for example." So now it i OK for 5 hours?
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Basic LCD TV and Monitor troubleshooting guides.
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Voltage Regulator (LDO) testing:
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Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

Tear down pictures : Hit the ">" Show Albums and stories" on the left side
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TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Old 06-01-2014, 11:42 AM   #22
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Default Re: Dell 2007WPF Flickering Off

Howdy fellas. This is my first time posting here and I couldn't help it but give my input on this particular monitor as I am currently fixing the same model with the exact same problem. I was able to trace my issues down to the 2SK3548 transistor. I could hear mine clicking during the power cycling and the check with the multimeter backed me up on this. I'm going to order the part today.
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Old 06-01-2014, 04:41 PM   #23
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Default Re: Dell 2007WPF Flickering Off

It will help if you tell us where this 2SK3548 is at and what its designator (Q????) is.
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Old 06-01-2014, 04:50 PM   #24
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Default Re: Dell 2007WPF Flickering Off

Thats a large to3p fet, most likely Q601 main power supply fet.
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Old 06-01-2014, 04:54 PM   #25
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Default Re: Dell 2007WPF Flickering Off

"I could hear mine clicking during the power cycling and the check with the multimeter backed me up on this." It sounds like the power supply is in the shutdown/run loop due to detection of over current, bad startup cap. etc.
We will find out when he installs the new part.
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Old 06-02-2014, 08:30 PM   #26
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Default Re: Dell 2007WPF Flickering Off

Quote:
Originally Posted by bammbammfran View Post
well, that is not what you posted the first time !!
"As you can see, monitor is on and power button is yellow (its orange when computer is off) but screen is black."
Might be weak bulbs, could be a power supply issue which is why I recommended changing those caps too while it was apart
Sorry, I guess my wording didn't come across clear in the OP.

"The front panel buttons still glow yellow as usual, so power is still going through." That's what I meant that the monitor stays on but nothing displays on the screen.

Now since my last post, I've used the computer pretty extensively, usually 4+ hours a day without incident - until today. Screen's been "off" for the past 10 minutes now.

I was lucky enough to capture the behaviour on camera. Sorry about music...

https://vimeo.com/97181812

@ john I'll try to listen for clicks next time but I haven't heard any such thing from mine. If you could clarify with an update, that might help.

Thanks again all.
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Old 06-02-2014, 08:35 PM   #27
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Default Re: Dell 2007WPF Flickering Off

Quote:
Originally Posted by bammbammfran View Post
looks lit in the picture ????
Try it in a dark room or look at the monitor from the back (this might show light leaking out through some small holes

post a full picture of the back ?
Hmm, here's a pick with lights turned off...

It doesn't look that bright in person, that's the camera but the screen is "on", no display though.
Attached Images
File Type: jpg DSCN0915.jpg (626.4 KB, 12 views)
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Old 06-02-2014, 09:50 PM   #28
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Default Re: Dell 2007WPF Flickering Off

It appears that it stays lit as far as the backlight are concerned
This can be sometimes be confirmed by light shining out through holes in the back of the lcd panel.
If that is the case, the power supply and inverter are probably ok and the issue could be in the main input board

Near the plug that has the wires that power the main board are two black chips that have 3 pins on one side (center pin might be clipped back) and there is a larger tab on the opposite side of the pins
What are the numbers on those two chips.
DO you have a dc voltage tester ?
on the video, I Did not really see flickering , but it looks like it blacked out and then came back on by itself ? Is that what it did or did you unplug something to make it black out ?
You can try to disconnect the usb board from the main board to eliminate that as a possible power sucker.
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Old 06-03-2014, 01:43 PM   #29
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Default Re: Dell 2007WPF Flickering Off

Quote:
Originally Posted by bammbammfran View Post
You can try to disconnect the usb board from the main board to eliminate that as a possible power sucker.
I dont think it will work at all if you do that?

I have always believed the 3.3v to the main board was delivered from the usb board - see budms teardown here
http://www.badcaps.net/forum/showthr...ight=dell+2007
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Old 06-03-2014, 01:52 PM   #30
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Default Re: Dell 2007WPF Flickering Off

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I dont think it will work at all if you do that?

I have always believed the 3.3v to the main board was delivered from the usb board - see budms teardown here
http://www.badcaps.net/forum/showthr...ight=dell+2007
That is correct, the 19VDC from the power board is fed into the USB/SUB-POWER SUPLY to buck converters to generate the 5V, 3.3V etc.
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Old 06-03-2014, 03:17 PM   #31
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Default Re: Dell 2007WPF Flickering Off

ok
The posted pictures were not complete enough for me to see that
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Old 10-25-2014, 07:08 AM   #32
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Default Re: Dell 2007WPF Flickering Off

Quote:
Originally Posted by bammbammfran View Post
It appears that it stays lit as far as the backlight are concerned
This can be sometimes be confirmed by light shining out through holes in the back of the lcd panel.
If that is the case, the power supply and inverter are probably ok and the issue could be in the main input board

Near the plug that has the wires that power the main board are two black chips that have 3 pins on one side (center pin might be clipped back) and there is a larger tab on the opposite side of the pins
What are the numbers on those two chips.
DO you have a dc voltage tester ?
on the video, I Did not really see flickering , but it looks like it blacked out and then came back on by itself ? Is that what it did or did you unplug something to make it black out ?
You can try to disconnect the usb board from the main board to eliminate that as a possible power sucker.
Sorry to drag this old topic up again. So since I was last here - I replaced I took in the power inverter board and had the caps replaced. Issue came up again.

Then I bought another (used) inverter board and swapped that in. Things appeared fine (symptoms appeared briefly once or twice) until today where its reared up its head. It seems particularly bad when I'm playing a game and rather inconvenient.

A bit tight for funds atm - so I have one shot at this. What are the chances its still an issue with the power inverter and the used on was a dud too? Vs perhaps an issue with the driver board (where the inputs are plugged in) or even the power supply board itself?

Thanks
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Old 10-25-2014, 07:20 AM   #33
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Default Re: Dell 2007WPF Flickering Off

I just watched the video. It looks like the picture goes out but the backlights and power LED stay on. Is that correct?
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Old 10-25-2014, 03:56 PM   #34
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Default Re: Dell 2007WPF Flickering Off

^ Exactly.

Last edited by aatroxed; 10-25-2014 at 04:07 PM..
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Old 10-25-2014, 05:02 PM   #35
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Default Re: Dell 2007WPF Flickering Off

It's not the inverter then, if the backlights stay on. Plus if it was, replacing the inverter would probably have at least changed the fault somewhat.

I did see earlier you had the idea it may be your PC. It is possible a faulty video card could cause loss of signal but not cause a "no signal input" message.

Before trying the hard stuff, have you tested your computer with a different monitor, or your monitor on a different computer?
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Old 10-25-2014, 08:51 PM   #36
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Default Re: Dell 2007WPF Flickering Off

Since making the original post I have upgraded my video card - so I'm fairly sure it isn't the video card (unless its my psu not feeding enough power to the card?).

I will hook up the monitor to my macbook and ill see if the issue comes up again. Unfortunately, no second monitor atm.
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Old 10-26-2014, 08:43 PM   #37
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Default Re: Dell 2007WPF Flickering Off

But to reiterate - The monitor on its own, powered on and with no input connected - should always display an image by itself - a bouncing "no dvi input" etc. Mine doesn't when the problems crops up. That's why I've ruled out that its a video card issue.

The problem happens whether its hooked up or not.
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Old 10-27-2014, 01:40 AM   #38
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Default Re: Dell 2007WPF Flickering Off

OK. I think the next step is to check all the power supply rails when the monitor is working and not working, to see if there is any change in any of them between the two states.

You should also do the same with any secondary regulators on the mainboard (there will probably be a couple at least).

If you are not sure what the regulators look like etc, post a top-down photo of the board showing all components and we can locate them.

Last edited by Agent24; 10-27-2014 at 01:42 AM..
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Old 11-02-2014, 02:02 PM   #39
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Default Re: Dell 2007WPF Flickering Off

Quote:
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OK. I think the next step is to check all the power supply rails when the monitor is working and not working, to see if there is any change in any of them between the two states.

You should also do the same with any secondary regulators on the mainboard (there will probably be a couple at least).

If you are not sure what the regulators look like etc, post a top-down photo of the board showing all components and we can locate them.
I'll take new pictures but are they not included in the original post that has pictures attached?

How would one check the supply rails? Would I need electrical equipment for that? If so that would be out of my depth; expertise.
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Old 11-02-2014, 03:35 PM   #40
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Default Re: Dell 2007WPF Flickering Off

^^ you would need a digital multimeter^^

I have a couple of queries.
Pic5 in post6 can you take a straight on clear picture of that board.
Do you know if that swirled residue on the board is flux or has something been spilled on it ever.
In the still pictures it looks like the back light is on but in the video it looks
to go fully black - can you do a video in the dark?
As you suggest the "new" inverter board could have caps that have gone bad
and we never found out what caps were used on the "old" board - do you still have it?
What make are the caps on the main board (with the inputs on)
Have you tried with a vga cable instead of dvi?
Have you checked the lvds cable is fitted firmly at both ends and check if the
insulation on the individual wires looks good. (not cracked or starting to crumble)

Last edited by selldoor; 11-02-2014 at 03:37 PM..
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