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Old 01-23-2011, 08:14 PM   #41
Ritalin
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Default Re: Dell 2007WFP Won't Power On

@peterfares (if you still are watching this post): One thing you might want to fix (and I don't know if you did or not) is to resolder the plug in. I picked up this monitor for free on craigslist and replaced all the capacitors and it somewhat worked, I noticed that this was completely coming undone and resolder it and it now works 100%!. And yours looks like it might be starting to do that as well.



@core2kid: Make sure to check for cold soldering, as now I've seen 3 different monitors have this issue. (On top of what retiredcaps/PlainBill said)
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Old 01-23-2011, 09:23 PM   #42
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Default Re: Dell 2007WFP Won't Power On

Are there any specific areas I should be checking for cold solders?

I don't have any idea where to start to even look for the voltage regulators. I have an idea of where the diodes are though (Are they the two by the 12v power connector?

How do I check them with a digital multimeter?

Here's some pics of my board. Do you all need better pics or pics of the back? If so, I'll be able to post better pics that I can take in daylight.





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Old 01-23-2011, 10:55 PM   #43
Ritalin
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Default Re: Dell 2007WFP Won't Power On

Yes, we'd like to see both sides of the board and in better light, keep in mind we're looking at rather small parts through the computer. So make sure the whole board takes up the picture.
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Old 01-23-2011, 11:09 PM   #44
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Default Re: Dell 2007WFP Won't Power On

Sure thing, I'll do it tomorrow afternoon after college. Thanks again for helping me out!
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Old 01-24-2011, 12:05 AM   #45
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Default Re: Dell 2007WFP Won't Power On

Quote:
Originally Posted by core2kid View Post
I don't have any idea where to start to even look for the voltage regulators.

How do I check them with a digital multimeter?

Here's some pics of my board.
1) Voltage regulators (U designation) can be bad. They can be shorted or output the incorrect voltage. The test described below only tests the former.

If you have a manual range multimeter, set it to 200 ohms (two hundred). You can test voltage regulators "in circuit" for shorts by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms
b) black on pin 1- red on pin 3 - record ohms
c) black on pin 2- red on pin 3 - record ohms

If any ohm reading is less than 30 ohm you might have shorted voltage regulator. Remove from circuit and repeat the tests to verify.

2) To test a diode in circuit,

a) put your multimeter in diode test mode
b) put your black lead on one side and the red lead on the other - record reading
c) reverse the leads - recording reading

A good diode should read 0.4V to 0.7V in one direction and 0L in the other. If you get a reading in both directions, you will have to desolder one leg and retest to verify.

3) PLEASE follow the instructions in PlainBill's signature on how to post pictures so they are posted here and please don't post inline.
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Old 01-29-2011, 04:06 PM   #46
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Default Re: Dell 2007WFP Won't Power On

Sorry for the delay all, I'm still waiting for a good sunny day when I can take pics. I've been hit by the east coast storm and I haven't had a good sunny day yet, just dull days :/
I'm hoping to have pics for you tomorrow.
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Old 01-31-2011, 03:32 PM   #47
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Default Re: Dell 2007WFP Won't Power On

Here are some pictures of the board.
Attached Images
File Type: jpg DSC00133.jpg (874.3 KB, 265 views)
File Type: jpg DSC00136.JPG (1.37 MB, 205 views)
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Old 01-31-2011, 03:39 PM   #48
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Default Re: Dell 2007WFP Won't Power On

Not that this is the fix, but is that some cold soldiering on the upper left picture of the back side of the power board?
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Old 01-31-2011, 04:39 PM   #49
core2kid
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Default Re: Dell 2007WFP Won't Power On

I tried to reheat most of the solder points, maybe I missed that one. I'll try it tonight and post back.

I can however say that occasionally it'll power on for 2 seconds and then start flashing.
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Old 01-31-2011, 10:46 PM   #50
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Default Re: Dell 2007WFP Won't Power On

I resoldered that and it didn't work. Any other suggestions?
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Old 02-01-2011, 10:37 AM   #51
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Default Re: Dell 2007WFP Won't Power On

Quote:
Originally Posted by core2kid View Post
I resoldered that and it didn't work. Any other suggestions?
Try checking the fuses circled below. With power off and your meter set to resistance, place your probes across each fuse. Reading should be around 0 ohms.
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Old 02-01-2011, 08:36 PM   #52
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Default Re: Dell 2007WFP Won't Power On

All the fuses read .00 to .02 Ohms, they also show continuity. Could one of the capacitors have failed?
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Old 02-25-2011, 10:44 AM   #53
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Default Re: Dell 2007WFP Won't Power On

Sorry to bring this old thread back to life but I'm still trying to get this monitor back up. I'm using a CRT for now. Any ideas on what may have failed of the USB board?
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Old 02-25-2011, 11:45 AM   #54
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Default Re: Dell 2007WFP Won't Power On

See post 45 to test the voltage regulators and diodes.

Are you saying that if you hookup a working computer with your favourite wallpaper that the computer shows the wallpaper for 2 seconds and then go to black?

If yes, you could have

a) bad capacitors
b) bad inverter transformer
3) bad ccfl
4) bad ccfl wiring/soldering

For the all of above, see starting with post #13

http://www.badcaps.net/forum/showthread.php?t=10419
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Old 02-25-2011, 01:44 PM   #55
core2kid
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Default Re: Dell 2007WFP Won't Power On

I have 2 of these monitors, one is my dads and this one was mine. Basically when it went out, I replaced the USB board with one from a known working monitor and it worked fine. That rules out #3 and #4.

About it working, occasionally it'll work but it'll only go as far as to turn on the backlight for a second and then it'll go off. This happens about 5% of the time.

All capacitors aren't bulged out or leaking. Could they still be bad?
What's the inverter transformer?
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Old 02-25-2011, 02:07 PM   #56
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Default Re: Dell 2007WFP Won't Power On

One thing you could try is measuring the voltages at the power connector of the usb board. It looks like the pins are labeled 1-6 and 7-12. Try measuring the voltages with the "good" board installed and again with the "bad" one installed. Also, measure voltages while pushing the on/off button on the front panel. Compare the voltage output of the two boards. If you find a major difference, then try to trace what that pin is connected to.


Yes, a cap can be bad. However, since you have no way of testing them, you'd be replacing them based on a "hunch".
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Old 02-25-2011, 02:10 PM   #57
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Default Re: Dell 2007WFP Won't Power On

Okay, i'll work on replacing the caps first. Can I test a cap with a multimeter?

I don't want to take apart the other monitor at the moment, my dad needs it every day and if something goes wrong, I'm dead...
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Old 02-25-2011, 02:28 PM   #58
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Default Re: Dell 2007WFP Won't Power On

Other than a dead short, you will not be able to test cap with a DMM. Replace with good quality caps like panasonic FC or FM series from digikey.com.
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Old 03-13-2011, 04:22 PM   #59
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Default Re: Dell 2007WFP Won't Power On

Hi there! Iīm also trying to repair a 2007wfp dell monitor, had replaced a shorted J598 mosfet, and the two diodes S4 62A (with similar FU4007: 1000V, 1A, 75ns) (one of the S4 diodes was shorted) and also the 3A fuse.
But the result is that I still get a short and is caused by the ZD701 (very little zener diode, the only one on the pcb)
Does anybody know of a proper replacement? I canīt get to figure wich voltage is it suposed to work with, guessing for the size that itīs a 1/4W diode.
Thanks for your wisdom!
Chad
PW: I think pcb voltages are 19V and 5V for the usb, but do not know if thereīs another/s.
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Old 03-13-2011, 05:06 PM   #60
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Default Re: Dell 2007WFP Won't Power On

Quote:
Originally Posted by chad720 View Post
Hi there! Iīm also trying to repair a 2007wfp dell monitor, had replaced a shorted J598 mosfet, and the two diodes S4 62A (with similar FU4007: 1000V, 1A, 75ns) (one of the S4 diodes was shorted) and also the 3A fuse.
But the result is that I still get a short and is caused by the ZD701 (very little zener diode, the only one on the pcb)
Does anybody know of a proper replacement? I canīt get to figure wich voltage is it suposed to work with, guessing for the size that itīs a 1/4W diode.
Thanks for your wisdom!
Chad
PW: I think pcb voltages are 19V and 5V for the usb, but do not know if thereīs another/s.
Earlier today I saw this thread. The gentleman provided a good description of the problem, just like you did. He ALSO provided pictures and a datasheet. This changed a 10 or 20 post problem into a simple analysis.

The best solution to your problem is to identify the zener diode. Many SMD components have a two or three character marking code on the device. With that information, identifying it becomes easy.

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