Dell 2005FPW LCD Monitor Repair

[gdmorgan]

I am trying to fix the following computer monitor - thanks in advance for any advice!

Description:

Dell 2005FPW LCD Monitor (20”)

Problem:

No display. Screen is black, no signs of dim blacklight.
Green power LED light on solid (not flashing)
Green input selector LED light on solid
I have plugged into several computers, get same problem.

Tried So Far:

I have inspected the power and video boards and do not see any signs of bad capacitors. No bulging, smells, etc. I have removed two capacitors that commonly go bad on the power board, and they tested ok. I have re-soldered them to their proper location.

What's Next:

Looking for recommendations from other members on what to try next. I am somewhat of a noob when it comes to electronic repair but I am careful and willing to learn. I found a schematic from Dell and have included images of the inside of the monitor. I wonder if I should test the boards under power using the supplied schematic? If anyone could provide some guidance, that would be helpful. Removing and testing each capacitor from the board is another option, but this takes a while and is perhaps not the best option.

My Toolkit:

Klein Tools MM2000 Multimeter
Husky Mini Screwdriver Set
Soldering Setup

[budm]

Re: Dell 2005FPW LCD Monitor Repair

There is a white connector on the power supply/inverter board that is connected to the main board. Measure the DC voltage (Black probe to the metal chassis) at the ON/OFF pin, it should be >3VDC when the monitor is turn on, <1V when the monitor is turn off, that pin is the control pin for turning the backlights ON/OFF.

[gdmorgan]

Re: Dell 2005FPW LCD Monitor Repair

Hello budm,

Thanks for the reply! So I tested the ON/OFF pin on the white pin connector on the power board, and I got less than <1 V, even with the power cable connected. So I guess that means there's a problem with the power board, as suspected. Any way to test specific components on the board, based on supplied service manual? Thanks,

G-man

[retiredcaps]

Re: Dell 2005FPW LCD Monitor Repair

So I tested the ON/OFF pin on the white pin connector on the power board, and I got less than <1 V, even with the power cable connected. So I guess that means there's a problem with the power board, as suspected.

The main board is responsible for signalling the ON/OFF pin. If that pin is not going high (> 3V), the problem likely lies with the main board.

Test the voltage regulators on the main board as per troubleshooting guide in budm's signature above or mine below.

[gdmorgan]

Re: Dell 2005FPW LCD Monitor Repair

Budm & Retiredcaps,

Thanks for the replies. Ok, so before I had tested the power board on its own, not while it was attached to the main board. It is very difficult to test the On/Off pin on the power board while all the components are attached, because to do that the board is upside down in the metal chassis, and it's hard to access. However, I was able to connect all components except some cables on the LCD screen and re-test the On/Off pin connector on the power board.

The results of my test are 2.8 volts at the On/Off pin. Still short of the >3 volts expected.

Do I need to have everything on the monitor connected as usual in order to test? Or can I leave the LCD portion disconnected?

I am reading through retiredcaps' manual on testing the voltage regulator and will try this tomorrow and let you know what I find.

Thanks,
G-man

[budm]

Re: Dell 2005FPW LCD Monitor Repair

You can leave the flat ribbon cable not connected to the LCD panel which will allow you to be able to connect the lamp's wires to the power supply board (no need to remove the board from the chassis) so you can test the test point with the board facing you, that is how I do it. just make sure you still have it connected to running PC and do not touch anything on the board with your hands, to be safe, plug the monitor into GFCI outlet.

[gdmorgan]

Re: Dell 2005FPW LCD Monitor Repair

Budm & retiredcaps,

I connected the components as you suggested and tested this morning.

2.8V at the On/Off pin on the power/inverter board.

I also noticed that when the monitor is plugged in, the LCD display flashes white for a second or < 1 sec, just before going completely dark.

I will test the voltage regulator today. Thanks,

G-man

[budm]

Re: Dell 2005FPW LCD Monitor Repair

2.8V is enough so it is OK, then the problem is in the inverter circuits.

[gdmorgan]

Re: Dell 2005FPW LCD Monitor Repair

Budm & retiredcaps,

Holy crap you guys are geniuses. So I checked the voltage regulators, and the results are pretty incredible. I have four voltage regulators on the main board, all checked out with perfect numbers, except for one, which read 0 on all three pins. So I think it's obvious where the problem lies. Now I can't wait for a reply on the next step of the process! Below are my test results:

1117 (A?) S 33

pin 1 = 0
pin 2 = 0
pin 3 = 0

1117 (A?) S 18 (or S 10, it's difficult to read)

pin 1 = 0
pin 2 = 1.8
pin 3 = 3.33

1117 (A?) S 33

pin 1 = 0
pin 2 = 3.29
pin 3 = 4.97

1117 (A?) S 25

pin 1 = 0
pin 2 = 2.5
pin 3 = 4.74

[gdmorgan]

Re: Dell 2005FPW LCD Monitor Repair

Attached are two photos of the bad voltage regulator, one macro and one zoomed in (micro).

The top of the regulator reads:

F (?) F5 (?) J
1117 (?) S33

I believe this to be the replacement:

http://www.mouser.com/ProductDetail/...iO3xk7OC0Y3mgh

I am not sure if mine is a 1117 S33 or a 1117 AS33. Have I selected the correct voltage regulator?

My other question is - based on the voltage test, can I narrow the problem down to the voltage regulator and not bad capacitors or fuses?

Thanks!
G-man

[gdmorgan]

Re: Dell 2005FPW LCD Monitor Repair

Possible replacement part from Digikey:

http://www.digikey.com/product-detai...OSCT-ND/660708

[budm]

Re: Dell 2005FPW LCD Monitor Repair

Since the regulator is not getting any input voltage, then the output will be 0V, you need to trace out where the Input pin (the Right pin (pin3) as shown in your picture is the input pin) of the regulator is connected to to see why you are getting 0V reading. It is 3.3V Fixed voltage regulator. U501 is the one that feed the voltage to that regulator. That reading may be normal since it is for the USB HUB circuit section. Plug USB device into the USB connector and the USB output port to the PC, then see if the voltage will appear. See SCH of the service manual page 30.
So far, I would say that the problem is in the inverter circuits.

[retiredcaps]

Re: Dell 2005FPW LCD Monitor Repair

So far, I would say that the problem is in the inverter circuits.

Especially if the screen comes one for 1 second and goes off. Curiously, the list of guides I referenced earlier has such a troubleshooting guide.

[sodeepthinker]

Re: Dell 2005FPW LCD Monitor Repair

Hi gdmorgan. I have the same unit and repair in progress. But that chip u101 on the power board is totally burnt that you could not read the part no. And the manual schematic diagram does not exactly correspond to the actual power PCB. I would greatly appreciate it if you could tell me u101 actual part number. Thanks in advance.

[gdmorgan]

Re: Dell 2005FPW LCD Monitor Repair

Hi sodeepthinker,

Do you mean u501 or u101? I found u501 but not u101. Could you attach a photo or give me an idea where the part is on the board? I can get you the information you need. Thanks,

gdmorgan

[budm]

Re: Dell 2005FPW LCD Monitor Repair

Are you asking about U101 SMPS IC TO-220 mounte on the heat sink on the power supply/inverter board?
P/N TOP249YN?
http://www.digikey.com/product-detai..._id=PLA_865356

http://s807.photobucket.com/user/bud...ml?sort=3&o=17

[sodeepthinker]

Re: Dell 2005FPW LCD Monitor Repair

Great!! That's exactly my thing budm. gdmorgan, yes it's the smps ic on the heatsink. Oh, that was quick. Thanks alot to you guys. you just save my day.

sodeepthinker

[gdmorgan]

Re: Dell 2005FPW LCD Monitor Repair

Hello budm,

I've read the repair guides and am kind of stumped on what to try next. You said you think the problem lies in the inverter circuits. Anything specifically you could recommend for me to check? Hoping to give it one more go! I'd be stoked to fix this thing and not have to take it to the scrap yard.

[Misterkeeks]

Re: Dell 2005FPW LCD Monitor Repair

I cannot start a new thread, but as I have the same monitor I assume the issue will be similar. When I plug mine in, there is no indication of power. The green power LED on the front does not light. There is a high pitched whine from the power supply area. All of the components on the board appear fine. My multimeter died, but I will be getting a new one and a capacitance meter soon (hopefully). Anyone have an idea of the issue?