Dell 2007WFP Won't Power On

[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

That does not sound good.

[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

The 12V should come on when you hit the power switch, at least the 5V switching power supply is working but not the 12V. The 12V is for the Dell powered speakers sound bar so it does not matter at this point.
So when you hit the power button, does the power LED come on?

[MEB]

Re: Dell 2007WFP Won't Power On

Yes it does.

[budm]

Re: Dell 2007WFP Won't Power On

That mean the logic/main board is doing some thing, then you should also see the backlights flash on. Make sure to have this plugged into running PC while testing.

[MEB]

Re: Dell 2007WFP Won't Power On

Sorry for the late response. Had to do some real work today. Got a PC hooked up using vga. With 3.3 supplied from the power supply, I can cycle the power on/off using the power button on the monitor and the power LED turns on and off. The number 1 (designating vga) lights as well as number 4 (composite). These 2 numbers turn off/on in sync with the power LED as the power button is cycled. Then with 120 applied to the monitor, in addition to the 3.3 I am supplying, the power LED and the number 1 and 4 LED, cycle with the pressing of the switch. Also when the power is pressed on, I can measure 5V out of Q14 and 11.85V out of Q2, but no 12V from Q9. I do not see the backlights doing anything. I did see them at the time of my previous post if the screen looks like a light gray background with not much intensity which cycles with power on/off. But I am not seeing anything but a black screen now. I have never had this monitor connected to a PC during my adventures here. Could I have screwed something up by not doing that?

[budm]

Re: Dell 2007WFP Won't Power On

The grey glowing screen means the T-CON board is not active due to no power to it or blown fuse on the T-CON. It seems to me that this unit has more than one problem. I expect the backlights to come on at least. Do you get any DC voltage at the fuse on the inverter board?

[MEB]

Re: Dell 2007WFP Won't Power On

I am having trouble finding a fuse. Unless it happens to be this FP801 which I have circled on the attached photo. If that is a fuse, I am reading around 10V on one side of it.

[budm]

Re: Dell 2007WFP Won't Power On

That is the fuse, it should have 19VDC which comes from the main power supply board, that power supply board has only single output, 19VDC.

[MEB]

Re: Dell 2007WFP Won't Power On

You are right. It reads 18.95V. Fuse is open and removed from board. It is obviously a 5A Littlefuse from the markings but being unfamiliar with this type of fuse I couldn't find whether it is a fast or slo blow so didn't obtain replacement yet.

[craftsman1234]

Re: Dell 2007WFP Won't Power On

You are right. It reads 18.95V. Fuse is open and removed from board. It is obviously a 5A Littlefuse from the markings but being unfamiliar with this type of fuse I couldn't find whether it is a fast or slo blow so didn't obtain replacement yet.

Jumping into this thread. I have the same board. I've removed this fuse and testing it on the multimeter ohm setting shows nothing. So I am assuming it is blown. Did you ever find what the replacement part is for this and who to order it from?

[budm]

Re: Dell 2007WFP Won't Power On

Littlefuse PICOII fuse, Fastblow, that is what I use. You can get it from DIGIKEY or MOUSER.

[craftsman1234]

Re: Dell 2007WFP Won't Power On

Littlefuse PICOII fuse, Fastblow, that is what I use. You can get it from DIGIKEY or MOUSER.

budm,

Thanks for the fast reply. Does this look like the correct one?

http://www.newark.com/jsp/displayPro...36896901|plid|

The color seems to be different from what I have (Yellowish). The ones that I have seen in this color are slow blow.

Thanks.

[budm]

Re: Dell 2007WFP Won't Power On

This is the SLO-BLO that matches your original:
http://www.digikey.com/product-detai...45CT-ND/776707

[craftsman1234]

Re: Dell 2007WFP Won't Power On

This is the SLO-BLO that matches your original:
http://www.digikey.com/product-detai...45CT-ND/776707

Thanks, is it better to switch them to fast blow?

[budm]

Re: Dell 2007WFP Won't Power On

The fast blo may trip due to the in-rush current when the caps on the inverter board are first charged up. I would get the same as original.
One thing you need to do is to verify that the board does not have shorted out MOSFETs.

[MEB]

Re: Dell 2007WFP Won't Power On

I ordered some Mosfets, 40V 2A Schottkys, a 5V 1/2W Zener to replace ZD 701 and the 5A slow-blow Pico for the inverter board. I was getting impatient waiting for parts and the opportunity came up to acquire a working 2007WFPb reasonably so I took it with the intention that this would aid me in comparing measurements to fix my original monitor.

Now I am the proud owner of 2 broken Dells. The parts finally came in and I replaced them on the USB and Inverter boards and tried out the broken monitor. I still didn't have 3.3 Volts at Q6 but the zener was holding up and the inverter hadn't blown its 5A Pico. But I kept looking at the working dell in the corner and it got the best of me.

I disassembled it with the intent of finding out just exactly what boards were bad in the original monitor. I first connected my original LCD to the new parts and a pc. The screen worked fine. I left it in place. I then put my original power board in place of the working one and monitor worked fine. And so on yielding the following. My original USB board was still bad, my original logic board is bad, but my inverter with the replaced blown fuse worked fine as well as my LCD and power board. Not to push the issue, I powered the conglomeration off. Then I got to thinking I might as well write down a bunch of voltages from here and there before replacing the new monitor back together so I powered it back on and for about an hour I begain measuring what I thought would be key areas which would help me later on. I was measuring DC voltages on the J5 connector on the USB board and documented them which correlated to other's findings earlier in this thread and was having a grand old time but needed a break. 15 minutes later, I came back and had lost my buck regulator voltages! First thing I checked was F19 on the new USB board and it was blown. But it gets better. ZD701 is now shorted (again), my 3A F19 is blown (again), the new Pico on the inverter is blown (again) and the only thing different than before is Q6 is not shorted. I don't know for sure but I fear the new logic board got zapped also.

So in summation, I had a working monitor using my LCD, my power board and my re-fused inverter along with a known working logic board and know working USB board, so am I correct in assuming that either my original LCD, power board or inverter has some problem that decided to rear it's ugly head for the second time and destroy the same components? Or was it just a coincidence?

This is where, in the words of Dr. Sheldon Cooper, i say:

knock, knock ... budm

knock, knock ... budm

knock, knock ... budm

[craftsman1234]

Re: Dell 2007WFP Won't Power On

Wow, what a light show. The littlefuse came in today so I soldered it to the board today. All the caps had been replaced on this board and the power supply. Well once it was plugged in sparks flame and the smoke is out of the chips. I did not have good enough lighting to get photos of all the boards.

[budm]

Re: Dell 2007WFP Won't Power On

@MEB, I ran out of idea for you to check (I love that show).
@craftman, it probably has shorted MOSFET's so it blew the fuse the first time.