Dell 2007FPB teardown

[flemming_k]

Re: Dell 2007FPB teardown

After reading the https://www.badcaps.net/forum/showthread.php?t=10658
on Dell 2007. I found 2 of them today and took them apart to see how it is put together.
What I found are:
1) It only has one always on DC power supply output of 19V.

2) The 19V is fed to the Backlights inverter board.

3) The 19v is also fed (J4) the USB Hub/3 Buck converter regulators (3.3V (Q6) for the Logic board where the VGA/DVI, control panel are, 5V (Q14) (this 5V is also fed into 3.3V linear regulator for the USB interface IC) for the 4-port USB hub (these 4 USB ports are protected by 4 fuses), 12V (Q9) for the powered speaker bar DC output jack. This 19V is fed through 3A fuse. MOSFETs Q6, 9, and 14 are 2SJ598, P-Channel.

4) If the USB/Buck converter is not connected, the monitor will not work.

5) The 3.3V output from the Buck converter is fed back into the logic board which feeds U13 (1.8V Linear regulator) and U5 (2.5V Linear regulator) to run the LOGIC IC's on the logic board.

6) One bad design in the Buck regulator is that they parallel 2 Schottky Diodes together (http://electronics.stackexchange.com...des-a-bad-idea) to try to get more current handling, but if you do not precisely match the Vf of the Diodes, the one with lower Vf will be on, the one with higher Vf may not be on at all. They should have use single 2 or 3A rating Diode instead of 1A rating, Diodes are rated at 1A 40V. This may explain why this model has the same failure mode due to shorted out diodes.

Hi Budm
My monitor goes black after a couple of hours. I guess the two parallel Schottky diodes could be the cause.
Could you show me in a picture where they are located?

Thanks
Flemmig_k

[WB1]

Re: Dell 2007FPB teardown

I know a very old thread - but thanks to everyone on it who suggested the resistors under 'The Blob' on the USB board - mine was the 15k one that had gone open - replacing it with another SMD one taxed me a bit with a a rather large Weller iron - but - it did the job and came back to life !

I also re-caped the PSU while I was about it - I should hopefully get a few more years out my favourite 4x3 monitor now !!

Thanks again.

WALLACE.

[Behemot]

Re: Dell 2007FPB teardown

Np. I'd recap it too, it's full of garbage, if that resistor does not kill it, the caps always do in the end.

[Muggz]

Re: Dell 2007FPB teardown

New inverter board came, transformers all tested 1050-1060, threw it in, broke a connector, three solder jobs later.... it lives! Now I get to wrestle with Windows 7. THANK YOU for your help, Badcaps community and special thanks to Behemoth!

[Behemot]

Re: Dell 2007FPB teardown

Strange thing is, that resistor is hardly ever burned. In most cases, it looks fine, sometimes even measures fine, but still…

[gastorro]

Re: Dell 2007FPB teardown

The above ^^ pics at their original resolution..

https://ibb.co/4pBxsgk 
https://ibb.co/NjZCQLg 
https://ibb.co/yfQYXV7

[gastorro]

Re: Dell 2007FPB teardown

my pictures of that resistor

[gastorro]

Re: Dell 2007FPB teardown

...
The key discovery though was the 2.7k ohm resistor under the "dielectric" glue on the usb board.
Confirmation from other users that it was the cause of their issues gave me hope -- a chance of needing just one single "repair" to get my monitor working correctly.
Sure enough, the suspected resistor was dead when I uncovered and tested it.
Now I just had to replace it.
...
Amazingly... it all worked! The monitor works perfectly now.
Again, a huge thanks to ac21, budm, and the entire badcaps board.
...

I had exactly the same problem ( random reset ) due to that 2k7 burnt resistor.

Thank you!

[budm]

Re: Dell 2007FPB teardown

Check the resistance of the transformers of the new board first to see what you get.

[Muggz]

Re: Dell 2007FPB teardown

If it's so cheap, sure. You can actually use the whole replacement board, if it's sold as working.

I may get that lucky, we will see. It was sold as being pulled from a monitor with a cracked screen.

[Behemot]

Re: Dell 2007FPB teardown

If it's so cheap, sure. You can actually use the whole replacement board, if it's sold as working.

[Muggz]

Re: Dell 2007FPB teardown

Thanks! I wasn't sure how to look up and order transformers. It doesn't seem to be as easy as resistors. So I picked up an inverter board for $12 off of eBay. It should arrive in a week and hopefully I can pull one of the transformers off of that.

[Behemot]

Re: Dell 2007FPB teardown

If that's correct, first transformer's busted, that's what's making the driver shut down.

[Muggz]

Re: Dell 2007FPB teardown

Check the secondary sides of those three inverter transformers, if all six have the same (within 1-2 %) resistance.

I had no clue what you meant, and several YouTube videos later... lol (I like this though, I’m learning!)
Chip 1 - 878 and 1037
Chip 2 - 1029 and 1029
Chip 3 - 1020 and 1017

[Behemot]

Re: Dell 2007FPB teardown

Check the secondary sides of those three inverter transformers, if all six have the same (within 1-2 %) resistance.

[Muggz]

Re: Dell 2007FPB teardown

What should I do or check next?

[Behemot]

Re: Dell 2007FPB teardown

Phone's usually not enough, there are two polarisation filters 90° against each other so almost no light comes through, you need some strong light to se. However if the indicator LEDs are on, likely just the backlight is the problem.

[Muggz]

Re: Dell 2007FPB teardown

Does it shut down completely, or just the backlight?

I reassembled it just to test. Self test comes on for half a second, and then the screen goes black. The power light and the number 2 light stay lit. It does not appear to be backlit, and when I shine my mobile phone light on the screen I don't see anything. I ordered another multimeter on Amazon and expect it to arrive tomorrow. Thank you for responding.

[Behemot]

Re: Dell 2007FPB teardown

Does it shut down completely, or just the backlight?

[Muggz]

Re: Dell 2007FPB teardown

Hi everyone,

I have a Dell 2007FPb and found this thread with others experiencing my issue. My monitor turns on for about a half a second before the screen turns black. This is in the self test mode also. I took it apart and did not find any bulging or leaking capacitors. I tried replacing the 272 resistor others had mentioned in this thread, but it did not work and my symptoms are the same. Additionally I did not have a dielectric white blob on my board when I opened it like others have seen. See the last picture where I almost exactly copied someone earlier in this thread with a 1 W resistor.

I don't really know where to go from here. I really love this monitor, it was my favorite monitor because it was so bright and crisp and sharp colors. I would REALLY like to get it working. I have a multimeter, but I have never used one before, and it's a cheap harbor freight one. I don't know if it is up to the task but I will measure anything anyone asks me to measure and report back. Does anyone have any ideas please? I have included pictures front and back of all four of my boards below. Thank you so much for your time.

To try to fix this issue I have reviewed all of this thread and also a similar thread: https://www.badcaps.net/forum/showthread.php?t=8603