Dell 2007WFP Won't Power On

[MEB]

Re: Dell 2007WFP Won't Power On

budm,

I'm back. After our last conversation, I figured I was going to have to make me a sketch to help me understand things a bit clearer before getting back to the problem at hand. So I just finished my little schematic and went to fire up the beast again. It is in better shape then when we last talked.

I think last time when you had me try to power up the monitor, I was pressing the wrong switch. The monitor is face down on the bench and I slipped my finger in between the bezel and the table and thought I was hitting the power button, but since I couldn't see anything, I think I was off a switch. Anyway, this time I hit the right spot and have better news to tell you.

I have 3V at the drain of Q6 (cause I am injecting it.) I also have 5V at the drain of Q14, but no 12v at Q9. I do have 11.8+ at Q2 which is on my new drawing but I don't know what it is supposed to be or what Q2 is for. Looking between the bench and the screen, I do see a faint glow. There is DC Volts at the correct pins at J5 except for the 12 V.

I have to go watch the Cardinal game so will get back to this tomorrow.

[budm]

Re: Dell 2007WFP Won't Power On

That does not sound good.

[MEB]

Re: Dell 2007WFP Won't Power On

I have no 12V at L8 and no 5V at L11 per your drawing. I do have 19V at F19 now on both sides.

[budm]

Re: Dell 2007WFP Won't Power On

So there is no response from the main board then. The 12v and the 5V also not present on the that board either?

[MEB]

Re: Dell 2007WFP Won't Power On

No such luck.

[budm]

Re: Dell 2007WFP Won't Power On

So can you turn the monitor on and see the LED power light?

[MEB]

Re: Dell 2007WFP Won't Power On

OK, Got everything hooked back up as shown. Now at 3.3V on power supply I get 1.810A and am having way too much fun!

[budm]

Re: Dell 2007WFP Won't Power On

OK, I thought you have the boards connected back up, there was no load that is why it is so low. You need to connect the boards up.

[MEB]

Re: Dell 2007WFP Won't Power On

Yes, the 3.3V on the power supply did not change. I have Q6 and ZD701 still removed from the board and nothing else connected to the USB board at this time. It that alright?

[budm]

Re: Dell 2007WFP Won't Power On

So the output of the power supply is still at 3.3V? I am looking for heavy load due to shorted out and blown component due to that shorted Q6. I believe that the Current knob on the power supply is for setting the maximum it will allow the load to draw. If you are getting 3.3v and the current draw is only 2~4mA, then it seems to me that the logic board is dead. So far it does not look like you have shorts in the 3.3V line.

[MEB]

Re: Dell 2007WFP Won't Power On

OK. I warned you about not knowing anything. After your last reply, I got the power supply and read the instructions which amounted to a few pages and set off to educate myself. After a full afternoon, me, my meter and the power supply along with a little light bulb did some bonding and I think I understand enough to be dangerous. I ended up setting the power supply to 3.3 volts and read 55mA on both my meter and the power supply when all was hooked up to the light. It was a little 30V lamp but I could see the filament glow. I was satisfied I could read what the power supply was telling me so I hooked up to C44 as you told me to do without changing anything. I could only read 2-4 mA on the power supply. From what you thought I expected to see much more. Please advise.

[budm]

Re: Dell 2007WFP Won't Power On

You can connect the external power supply to C44, PLUS to the Plus of the cap, NEGATIVE to the negative of the cap. Just make sure that FD3, FD4 are not shorted or conduct both direction. Read post145 also.

[MEB]

Re: Dell 2007WFP Won't Power On

I got Q6 off without damaging the board but I broke the gate pin off trying to lift it off the board. S-D = .3 ohm out of circuit. I'm guessing he was done for anyway.

I have access to a BK Model 9110 100W Multi Range 60V/5A DC Power supply and will be reading up on how to use it if you think it might work. It has 2 digital readouts, one for Volts and one for Amps and it appears you can adjust them independantly using one knob and a selector button.

Getting ahead of myself, I looked over your drawing again and think maybe you would hook up the positive from the power supply on the board to where I removed the drain from Q6? And if so where would the ground get connected to? Then, how would you operate the power supply?

[MEB]

Re: Dell 2007WFP Won't Power On

Thanks so much for your reply. On Q6, S-D = .3 ohm, S-G = .5 ohm, G-D = .6 ohm. I will go ahead and remove Q6. I think I can get my hands on a variable power supply, but I will have to do some research first on how to use it and secondly, how to perform the test you want me to do. In the meantime, I will see if I can get Q6 off.

[budm]

Re: Dell 2007WFP Won't Power On

OK. Q6 is the Buck regulator swithcing power supply to produce the 3.3vdc for the Logic ICs. Does Q6 show very low Ohm reading between the Source and Drain? If that is the case, it can be real bad news, as you can see from my diagram, Q6 is basically in series with the load and it must be turned on and off at very high speed to do the switching for 3.3V output, when it stuck on (due to bad Gate drive signal from the SMPS IC or shorted out, the 19V will be at the out put and can easily wipe out anything that is made to handle only 3.3~5V range.
If I were you, I would remove Q6, then attach the variable power supply with built-in Amp meter to the 3.3V line. Then you slowly turn up the power supply while monitoring the current, if the current jumps up to 5A or more (I do not know the spec of this 3.3V power supply, I expect the current rating it can handle will be around 2~3A range, then the load is damaged also.
May be insanezz can tell us what the current draw is on the 3.3v Line.

[MEB]

Re: Dell 2007WFP Won't Power On

Hello,

I know very little about electronics and am quite intimidated about posting on this forum. I have a Dell 2007WFP which has the appearance of doing nothing when you push the switch. I have spent the last few weeks digging into it and reading everything available on the badcaps forum. budm, retiredcaps, plain bill, and others already have been my true mentors without knowing my existance. It took a couple of weeks to learn to use a digital camera and optimizing software to even come close to getting acceptable pictures to post, and since I am getting nowhere fast with my monitor, I guess I'll have to jump right on in.

I have attached (or at least attempted to) photos of a 5EL2J08001 USB/DC Converter board. After reading the forums, I am assuming my trouble lies on this board so will only post photos of it at this time.

Here's all I have done.

The forums lead me to this board and I know it has problems. I have a digital volt meter and first checked F19 and the 4 small fuses, F1, F2, F3 and F4. The little guys were fine, but F19 was bad. I was able to identify him via the internet and ordered some 3A Littlefuses to take his place. I received them and replaced him after watching soldering videos on YouTube where I learned about Chip Quik. I think I did OK since I have never even seen a surface mount device before now.

Also I read about the dangers of not investigating why a fuse blows in the first place, so I read more in circuit component testing from retiredcaps. I really wanted to put everything back and turn it on, but I resisted. I checked all 8 of the S4 65A devices which budm said were 40V 1A shottky diodes and I believe those to be good. I continued and read how to check zener diodes and Mosfet devices and became acquanted with their images on Google enough to find them on the board. So what I think I know now is fuse F9 was bad and replaced, ZD701 is shorted and removed and Q6 (J598) is also bad (not removed yet).

So now I must ask for help. First I have no idea how to find replacements for the zener diode and the Mosfet fellow and secondly I don't know what else to do. I only got this far from much reading of the articles here but I don't have a feeling for when it might be time to try to fire it up again. But until I can find replacement parts for the diode and Mosfet I believe I am at a standstill.

Please help me if you will.

[insanezz]

Re: Dell 2007WFP Won't Power On

Actually I already found 3 spare boards with LM2596 and it is working like a charm for now.
They seem to be some kind of integrated PWM or so, as they are not producing any heat at all, but I doubt if this will continue if the monitor is heavily used in the summer.
The best ting is that they have wide input voltage range and can produce manually configured output voltage at 2A stable if what was written is true.
And they were pretty cheap, too - like 1$
I'm planning to mount them on a plastic board which will replace the USB one and finish this project hopefully with success.

[budm]

Re: Dell 2007WFP Won't Power On

To use Linear regulator to drop 19V to 3.3V and 5V will cause lots of heat on the regulators, even the 12V regulator with 1/2A of current will still waste 3.5Watts of power. 5v reg @1/2A will waste 7W, 3.3V @1/2A will waste 7.85W. Current draws will more likely to be more than 1/2A.

[insanezz]

Re: Dell 2007WFP Won't Power On

Hi guys,
I'm having two of these monitors (2007wfpb) and they both failed their USB boards. On one of them the USB board was kind of working as it was flickering its voltages up and down (it was not able to power up the LCD at all), but this behaviour helped me to measure the voltages that are needed and are going out of it.
Anyway, if your logic board is alive, you need all 3.3V, 5V and 12V to be fed to the logic.
I gave it a try using a spare computer PSU as it has all required voltages.
So I fed them to J8 as shown in the following diagram:
---------
| X | X | You should not connect anything to the X places!
---------
| X | 12|
---------
|3.3| 5 |
---------
| X | G | G is GROUND
---------
| X | X |
---------
| X | X |
---------

In the end, both monitors are working fine, except they need an external computer PSU

P.S. I hope I can find a solution with 7805, 7812 and something for 3.3V in the future, so I can get rid of these PC PSUs.

[Jasgriff]

Re: Dell 2007WFP Won't Power On

Ohhhh no ur never giving up?

Nice job of the heat gun removal by the way!