Dell 2007wfp - 2 sec to black

[mojonba]

Hello,

Recently m 5 yr old Dell 2007wfp developed to what is described around here as the 2 second to black problem. After reading about this problem I begun to think it is an inverter problem. Unfortunately inverters for this monitor are not that cheap or plentiful so I came here to see if I could repair it. I opened the monitor to inspect the inverter and power supply. See pics hosted here. I don't see any bulging cap and I would like to know if I really should go ahead and replace all 5 inverter caps. Let me know if there is any previous troubleshooting step before I start replacing caps.

Thanks.

[tom66]

Re: Dell 2007wfp - 2 sec to black

If you flip the inverter board around, does it have a part number? I found my inverter for $10 + $4 shipping by googling the part number written on it. (Don't just search for the monitor model number + inverter because then you will get people charging a lot of money for them.)

I'm surprised at the lack of components on that PSU power supply. I guess it is a cost optimised design.

[mojonba]

Re: Dell 2007wfp - 2 sec to black

Yes I have looked for it online. It is P/N: 5EL2J04011. I is/was listed here for 49.99. I am unable to find it anywhere else.

[PlainBill]

Re: Dell 2007wfp - 2 sec to black

The two most likely causes of 'two seconds to black' are bad capacitors and bad CCFLs / CCFL wiring. A bad transformer is another possibility.

Far and away the best way to troubleshoot this problem is to hook up a known good CCFL and try substituting it for each original CCFL. If you don't have a known good CCFL, measuring the resistances of the transformer secondaries may detect a bad transformer.

Pictures will help us help you. Don't bother posting them somewhere else. Due to bad experiences, many people here won't look at them. Attach them to your post using 'Manage Attachments', below the text entry area.

PlainBill

[mojonba]

Re: Dell 2007wfp - 2 sec to black

I've posted the pics to the forum. I dont have an extra ccfl so cant troubleshoot with that. Where exactly can i measure the tranformer's secondary voltage?

Thanks.

[PlainBill]

Re: Dell 2007wfp - 2 sec to black

I've posted the pics to the forum. I dont have an extra ccfl so cant troubleshoot with that. Where exactly can i measure the tranformer's secondary voltage?

Thanks.

Don't try to measure the transformer's output voltage!!! It's about 1000 volts AC at 35Khz and can fry a DMM!!!

Good pictures, thanks. I'm lazy, it's late, and I'll be kept awake by idiots detonating illegal fireworks. Rather than mark up a picture, I'll describe it.

Note that the transformer has a white dot in one corner, and has 8 pins. The white dot indicates pin 1. The pins are numbered 1-8 counterclockwise. So the pins on the corners are 1, 4, 5, 8. 1-8 is one secondary, 4-5 is the other.

PlainBill

[jsog]

Re: Dell 2007wfp - 2 sec to black

That mustard-colored thing near the connector in the top of the first picture is a picofuse. If it's not blown, the resistance across it should be near zero.

[PlainBill]

Re: Dell 2007wfp - 2 sec to black

That mustard-colored thing near the connector in the top of the first picture is a picofuse. If it's not blown, the resistance across it should be near zero.

If the fuse is blown, you won't get anything. The problem is 'Two seconds to black'.

PlainBill

[jsog]

Re: Dell 2007wfp - 2 sec to black

Doh... I resolve to pay closer attention.

[PlainBill]

Re: Dell 2007wfp - 2 sec to black

Doh... I resolve to pay closer attention.

And please continue to help. The more people helping, the better.

PlainBill

[mojonba]

Re: Dell 2007wfp - 2 sec to black

Update:

I replaced all 5 caps in the inverter with Panasonic FC series caps. All went well. When I powered up the monitor I heard small arc kind of sound from the monitor's upper right corner. The backlight flickered at the same frequency as the arcing sound. Once the ccfl "warmed" up the backlight stopped flickering and the monitor seemed to be working normally albeit some sound from the same corner/ccfl. Turns out now, everytime I power cycle the monitor the ccfl flickers, some times even going 2 sec to black, when it does not go black it flickers for about a minute till it warms up and stabilizes. I am guessing I have a dying ccfl then? What exactly happened when I changed the caps? Why is the monitor viewable now and not before the cap change? Is the ccfl easily replacable?

Thanks.

[sam_sam_sam]

Re: Dell 2007wfp - 2 sec to black

This web site should have what you are looking for cclf tubes

http://www.ccflwarehouse.com/

[mojonba]

Re: Dell 2007wfp - 2 sec to black

Hello,

Although the monitor was viewable after a couple of power cycles, it now always goes back to black after 2 sec. So the capacitor replacement did nothing. Is there any way to confirm this is a ccfl problem if i have no spare ccfl? Should I replace the capacitors in the power supply?

PlainBill: I tried to measure the transformer secondary resistances but I don't have any continuity across any of the transformer pins? What am I doing wrong?

Thanks

[PlainBill]

Re: Dell 2007wfp - 2 sec to black

Hello,

Although the monitor was viewable after a couple of power cycles, it now always goes back to black after 2 sec. So the capacitor replacement did nothing. Is there any way to confirm this is a ccfl problem if i have no spare ccfl? Should I replace the capacitors in the power supply?

PlainBill: I tried to measure the transformer secondary resistances but I don't have any continuity across any of the transformer pins? What am I doing wrong?

Thanks

I've marked up a picture by circling the paired pins in the same color. Set your DMM to the 2000 (2K) ohms scale. Starting at the left, measure the resistance between the two points circled in black. If you get no reading try the 20K range. Record the number. Do the same for the two points circled in gray, reddish brown, red, orange, and yellow. Report the 6 numbers.

PlainBill

[mojonba]

Re: Dell 2007wfp - 2 sec to black

Black: 1.06
Gray 1.05
Dark Red:1.06
Red: 1.05
Orange: 1.05
Yellow: 1.06

Taken at the 20kohm scale.

[PlainBill]

Re: Dell 2007wfp - 2 sec to black

Black: 1.06
Gray 1.05
Dark Red:1.06
Red: 1.05
Orange: 1.05
Yellow: 1.06

Taken at the 20kohm scale.

Those readings indicate the transformers are probably good, but you are at the limits of your meter's resolution. Could you get any readings on the 2K (2000) ohm scale?

PlainBill

[Toasty]

Re: Dell 2007wfp - 2 sec to black

A cold solder joint on the CCFL will cause that arcing/flickering and the 2 secs to black. Shutdown circuit detects a lack of current or too high a voltage. Inspect that CCFL area where you heard the noise for arcing and a bad joint.

Can you flip the CCFL connections at the inverter board and see if the problem follows?

[mojonba]

Re: Dell 2007wfp - 2 sec to black

Yes, here they are.

Black: 1.067
Gray 1.062
Dark Red:1.073
Red: 1.067
Orange: 1.078
Yellow: 1.072

Toasty: the leads are not long enough to let me flip them.

[Toasty]

Re: Dell 2007wfp - 2 sec to black

>>Toasty: the leads are not long enough to let me flip them<<

Flip the board....?

[Th3_uN1Qu3]

Re: Dell 2007wfp - 2 sec to black

Your readings say the transformers are good. You have a problem with the CCFL wiring or the lamps themselves.