Dell 2007WFP(B) has 19V but no lower voltages

[zero10]

I am in the process of trying to repair 2 Dell 2007WFP (I can't recall if they are the B or not and don't have them in front of me right now so I can't check) monitors. I have torn them both down and I have found that they are both suffering from failed resistors on the large USB/power board (or at least that is the FIRST problem I have found). I have found a couple of other threads on here detailing problems and some solutions for these monitors and am trying to move ahead with repairing the 2 monitors I have.

https://www.badcaps.net/forum/showthread.php?t=25636
https://www.badcaps.net/forum/showthread.php?t=10658
https://www.badcaps.net/forum/showthread.php?t=20531

These are the threads I have read already. I hope I didn't miss it in one of the other threads but I am wondering if anybody has the pinout for the large power/USB board?

I hate working with line voltage and I have already figured out that I have 19V but none of the lower voltages present. I have a 19V power supply (what luck!) and I was hoping to make my repairs, then power up just this board on my desk to figure out whether I have brought up the 3 and 5V supplies before moving back to having exposed 120V (well, 170+V) components for further testing.

Thanks in advance!

[selldoor]

Re: Dell 2007WFP(B) has 19V but no lower voltages

I believe a common fault is the voltage regulators on the usb/power board.
I also thought you had to have the usb board connected to the others for it to work, my understanding is that 12v is fed from the power supply to that board which is used in the audio circuit and is regulated down to 5v and 3v which is fed back to the main board.
BUT there are a number different versions of the 2007 so I think we will need your board numbers to say for certain. I dont think we have any pinouts but in the middle therad in your list budm has kindly drawn some partial circuits for that board.

EDIT

This is THE thread
https://www.badcaps.net/forum/showth...007#post289258

[zero10]

Re: Dell 2007WFP(B) has 19V but no lower voltages

The main power board takes 120VAC and produces 19V, then passes that over to the large USB / other power board which regulates it down to 3V, 5V and 12V. The 12V is just for the speaker power bar port and nothing else. Some of the resistors under the silicone that are near the top of the board (for the buck converter controllers I think?) have gone open circuit or at least the value has gone up massively. The FETs and diodes all seem good (so far) and nothing on the board appears to be shorted (except the fuses of course). I was hoping just for the purposes of getting the 3V and 5V supplies working I could do the testing without having the 120V components connected.

[aortiz]

Re: Dell 2007WFP(B) has 19V but no lower voltages

can you post pictures please?

[selldoor]

Re: Dell 2007WFP(B) has 19V but no lower voltages

The main power board takes 120VAC and produces 19V, then passes that over to the large USB / other power board which regulates it down to 3V, 5V and 12V. The 12V is just for the speaker power bar port and nothing else. Some of the resistors under the silicone that are near the top of the board (for the buck converter controllers I think?) have gone open circuit or at least the value has gone up massively. The FETs and diodes all seem good (so far) and nothing on the board appears to be shorted (except the fuses of course). I was hoping just for the purposes of getting the 3V and 5V supplies working I could do the testing without having the 120V components connected.

Well I suppose you could introduce 19v - In that Must Read teardown thread by Budm he has written the voltages on the boards in the pictures I think I recall seeing a 19v pin marked on that usb board

[zero10]

Re: Dell 2007WFP(B) has 19V but no lower voltages

Just a quick update - I have done some further testing and have what appears to be good news. After reading the other posts again I saw mention of one fellow replacing his large usb / power board with universal DC-DC converter boards I decided that it was worth a try to do the same with mine.

I am worried that in removing the silicone from the power board to replace the resistors will damage something else so I have shyed away from trying this.

I swapped in 2 cheap deal extreme DC-DC converter boards and was able to get one of the monitors to power up and display the input selection popup (which was more than it would do before!) so I'm going to test the other one and if it seems okay I'll fabricate a bracket to hold these boards permanently and do some sturdier wiring, mount it all up and bring it to my desk for proper testing. Hopefully I'll have some results soon

[zero10]

Re: Dell 2007WFP(B) has 19V but no lower voltages

I didn't notice the 12V marking on this post:
https://www.badcaps.net/forum/showpo...&postcount=145

Which meant at first I had backlights with no display but once I rechecked everything and found that issue I was able to confirm at at least one of the monitors is fully functional with my replacement power solution. I'll try to get some work done in fabricating an alternate mounting system for these power boards and checking that all components are sized appropriately then I can fully assemble one of these monitors and give it a proper run to see if this solution will last.

I haven't had any luck getting enough of the silicone off the existing boards to be able to solder on them. I'll try some solvents when I'm back in the office next week and see if anything will loosen it.

[selldoor]

Re: Dell 2007WFP(B) has 19V but no lower voltages

I haven't had any luck getting enough of the silicone off the existing boards to be able to solder on them. I'll try some solvents when I'm back in the office next week and see if anything will loosen it.

Please can you post pictures of your boards - I dont recall seeing a lot of silicon on anyone elses?

[zero10]

Re: Dell 2007WFP(B) has 19V but no lower voltages

Sure. I don't have great lighting or more than a camera phone here at the office today so this isn't a troubleshooting picture, just a "here's what's wrong" picture

I have attached a picture of the failed resistors (mostly still entombed in silicone) and the monitor running with the makeshift power boards hanging out the back. I noticed that you don't actually need 5V for the monitor, only 3.3V and 12V so I reduced the board count to 2. So far they have been running 30 minutes and the heat sinks on them (which I applied) are at about 50-55*C. A little warm for my likes, I'll probably use higher current capable boards when I do the permanent repair, or actually repair the Dell boards themselves.

In the picture of the board with the silicone the resistors towards the right of the white strip of silicone have failed. One board has 3 bad resistors, the other has 2. I can scavenge the parts from one to fix the other, and if successful can order new parts for the part donor board, but I don't want to go digging in the silicone and damage the traces so I'm going to try to remove it chemically with little force. If successful I'll move ahead repairing the dell boards. If not, these cheap DC-DC regulator boards seem to do the job, the monitors just lose the USB hub and speaker bar power (not that I care)

[selldoor]

Re: Dell 2007WFP(B) has 19V but no lower voltages

Interesting set up - still wondering why the silicon is there - its not holding anything big in place - perhaps some high voltages on the big IC? so its to stop accidental touching.
With it set up do you have full control of the screen - dimming, colours and so on?

[budm]

Re: Dell 2007WFP(B) has 19V but no lower voltages

I use Silicone sealer which is in liquid from for sealing the grout, it soften up the silicone and you can just brush it off. So those resistors that failed, what are there values and do they fail open or shorted?
There is no high voltage in that area to burn up resistor in K Ohm range. The silicone may be used for moisture protection since it is in the high frequency switching circuits that drives those MOSFETs for the Buck regulator circuits.

[zero10]

Re: Dell 2007WFP(B) has 19V but no lower voltages

Does the silicone sealer leave any residue? These are such small components that anything left behind would be a problem, they are right on the limit of my soldering ability so I'm being extra cautious.

These resistors are not in a high power part of the board and they have gone open or very high resistance. Interesting that the other identical setup on the board is not covered in silicone. I wonder if with such small components and the silicone insulating them thermally if they eventually overheated and failed...?

The failed resistors should be in the k range, I don't have the board in front of me but I think they were 2.7k, 4.7k and 14k, but don't quote me on that

With my current setup everything works on the monitor, dimmer, multiple inputs, pip, everything that I could think to test.

[budm]

Re: Dell 2007WFP(B) has 19V but no lower voltages

One you brush off the old Silicone, then you clean the board with Isopropyl Alcohol.

[aortiz]

Re: Dell 2007WFP(B) has 19V but no lower voltages

can you find this liquid sealer at a hardware store?

[budm]

Re: Dell 2007WFP(B) has 19V but no lower voltages

I get my from HD, or Lowes, or ACE. similar to this
http://tile-guard.com/Product-Inform...ut-Sealer-16oz

[zero10]

Re: Dell 2007WFP(B) has 19V but no lower voltages

I've been able to remove enough silicone to get to the resistors however I can now no longer read the numbers on the top of them. I got frustrated with this so I just printed out some brackets to hold the DC-DC converter boards, cut down a piece of perfboard to mount a pin header on and built a small plug-in module that screws in where the original sat. Both monitors have been running for about a week without any issues using this setup.

I'm not against trying to fix these boards however I will need to find somewhere else to get the resistor values from in order to proceed.