Dell 2007WFP turning off/on by itself

[l433]

OK, I know that this question has been asked before, and I read most of the related threads, but couldn't find a solution to my problem.

I've had this monitor for about 7 years, and it had worked pretty much flawlessly until a week ago, when it suddenly turned off by itself. I checked the cables, unplugged/replugged the power, and it turned back on. But, after a few minutes, it turned off by itself again.
This time I unplugged the video cable, plugged the monitor in a separate power outlet, and just watched it. It turned off after a few minutes. The screen was completely black, and the power LED/button was also off. Then it turned back on after another couple of minutes. The animated DELL logo showed up on the screen - which to me indicated that the power had been completely cut off -and the monitor went into standby (no signal). Then after a while it cycled again, as above.

I've done some reading and saw that this is a fairly common issue, and supposedly related to bad capacitors. So I opened it up to take a look at the power board. But, after a thorough visual examination, and much to my disappointment, I couldn't see any sign of bad capacitors (a couple of pictures are attached).

So my question is, what now?

Thanks.

[budm]

Re: Dell 2007WFP turning off/on by itself

"This time I unplugged the video cable, plugged the monitor in a separate power outlet" So it is not connected to the running PC, then it will go into standby due to lack of the Video signal. The power indicator should stay green as long as the PC is attached, so if the Power indicator stays on with PC connected but no backlights, then you will look in the inverter circuits or the BL_ON signal which is generated by the main logic board. Running the monitor without PC connected will give you wrong false indication.

[l433]

Re: Dell 2007WFP turning off/on by itself

Thank you for your quick reply.

The behavior is identical with or without the PC and video cable attached:

1. The monitor seems fine, image is as good as ever, power LED is green.

2. The monitor turns itself off, the screen is black, the power LED is off.

3. The monitor turns itself back on, the DELL logo is shown on the screen, then the image comes back, the power LED is green again.

[budm]

Re: Dell 2007WFP turning off/on by itself

You cab monitor the DC voltage (about 18~19vdc, chassis ground for ground ref.) on the power supply board at one of the leg of inductor L702 which is connected to CN702 to see if this voltage goes away when the monitor stops working.

[ssheikh]

Re: Dell 2007WFP turning off/on by itself

So far I have owned four dell monitors. Three 2007FPs like yours and one U3011. I have had this problem on all four of them. Problem showed up a few months after the warranty expired.

On the 2007FPs the problem progressively got worse until the 5V buck converter on the USB board would die completely. The FET on there would short out and blow the fuse. Replacing the faulty components on the USB board would get it going for a month or two until the problem would come back and it would die again. Finally I got tired of fixing it and bought a few 2007FPs with cracked screens. Replaced the main board from those monitors into mine, fixed the USB board and now the 2007fps have been running ok for a few months.

And that is what my recommendation is to others. Just buy broken LCD monitors from ebay and replace the boards. It will be a lot cheaper than the hours spent in trying to fix them. I paid $35 each including shipping for the two broken 2007fp I got from ebay.

The boards on these monitors are very cheaply made and do not take kindly to soldering and desoldering. I have some very expensive soldering equipment and 25+ years of experience using it to mount and remove SMD components yet the tracks on these boards always come off the board and the board becomes a mess after just the first attempt to repair.

The U3011 I have not been able to fix yet. In fact its throwing its fits right now as I am typing this response. About 3 ~ 4 times a minute it dies and powers back up. Very annoying.

[ssheikh]

Re: Dell 2007WFP turning off/on by itself

Oh, and I should mention that the main power supply on all my monitors was ok. Output stayed steady on all of them without any noticeable ripple or noise on it.