Dell E207WFPc

[killian6pk]

Re: Dell E207WFPc

I rechecked the fuse and nothing appears to be shorting. The fuse still reads as good 0.1 ohm so it must be something else on the panel board. I have looked it over thoroughly several times and can't find another fuse. I have an ESR meter would it be worthwhile to check the smd caps. What should I be watching for number wise if I do that?

[killian6pk]

Re: Dell E207WFPc

You should post a picture of the Tcon,I will not be able to help you to much more with it.
But there are others that have repaired problems with them

Sorry for taking so long to reply, but I did not see this post on my computer until just now. The red dot in the first picture is just below where I replaced the fuse. It is the small white smd just out from the first regulator leg.

[killian6pk]

Re: Dell E207WFPc

Still waiting for some help with this TCon to see if there is anything else I can check in the way of components. Thanks

[PlainBill]

Re: Dell E207WFPc

Still waiting for some help with this TCon to see if there is anything else I can check in the way of components. Thanks

Look to the left of the connector, there is a square 28 pin IC. That is the controller for the dc-dc converter that provides the various voltages the LCD panel requires. You will notice a number of diodes and ceramic capacitors in that area. In particular the higher value ceramic caps are notorious for shorting. There are two approaches to testing these.

The simpler (but tedious) approach is to set your DMM to the diode test range and check all the diodes in both directions. Then set it to the 200 ohm range and check the resistance across all the caps. I would guess the caps should measure open on the 200 ohm range, but what you are looking for is a cap (or several caps in parallel) that read much lower that the others.

The quicker approach is to hook everything together, feed in a signal from a computer so the display should be on and start checking voltages across the largest caps. You are looking for ones that have 0 volts across them.

PlainBill

[killian6pk]

Re: Dell E207WFPc

Thanks Bill I will get started on this.

[killian6pk]

Re: Dell E207WFPc

Bill there were 4 Diodes in the area you mentioned. I have marked them with a red dot. The 3 small diodes with legs on diode setting all registered OF. The 1 regular type diode measured .531 one way and .159 the other.

OF the caps 4 measured 330.8 except one which was 365.0. There were 5 that measured 74.8 - 71.5. The 21 remaining measured OF . I am including the picture with the red dots on the diodes. There are several others that look the same, but are marked with a Q on the board.

Now I really need one of these:

[PlainBill]

Re: Dell E207WFPc

What is the number (marking code) on the three pin diodes (these are probably dual diodes)?

Are there voltage test points on the other side of the board?

The readings of 300+ ohms don't bother me, but the readings in the 75 ohm range seem too low.

PlainBill

[killian6pk]

Re: Dell E207WFPc

All the Diodes with legs read LD3.

The other side of the board appears to have all test points. I don't see any components on that side.

http://www.datasheetarchive.com/SMD%...datasheet.html

About 1/3 to 1/2 way down this page is a DataSheet from CYStech the model listed as BAT54SN3 says that it's top marking is LD3.

Let me know what I need to do next.

[PlainBill]

Re: Dell E207WFPc

All the Diodes with legs read LD3.

The other side of the board appears to have all test points. I don't see any components on that side.

http://www.datasheetarchive.com/SMD%...datasheet.html

About 1/3 to 1/2 way down this page is a DataSheet from CYStech the model listed as BAT54SN3 says that it's top marking is LD3.

Let me know what I need to do next.

I'm getting contradictory information; but it's easy to resolve. Googling BAT54SN3 takes me to a CYSTech datasheet that says the marking code is L44. It's easy to resolve, however. A picture of the pinout is attached. With a meter on the diode test scale you should get a voltage drop 1-3 and 3-2. Depending on the circuit and your meter, you may get a reading 1-2.

PlainBill

[killian6pk]

Re: Dell E207WFPc

Ok I will check that later on this afternoon. Have to run out for a couple of hours.

[killian6pk]

Re: Dell E207WFPc

This is what I got measuring the Diodes
Diode 1
Pin 1-3 = .236v
Pin 3-2 = .234v
Pin 1-2 = .462v

Diode 2
Pin 1-3 = .244v
Pin 3-2 = .234v
Pin 1-2 = .464v

Diode 3
Pin 1-3 = .234v
Pin 3-2 = .235v
Pin 1-2 = .465v

[PlainBill]

Re: Dell E207WFPc

This is what I got measuring the Diodes
Diode 1
Pin 1-3 = .236v
Pin 3-2 = .234v
Pin 1-2 = .462v

Diode 2
Pin 1-3 = .244v
Pin 3-2 = .234v
Pin 1-2 = .464v

Diode 3
Pin 1-3 = .234v
Pin 3-2 = .235v
Pin 1-2 = .465v

OK, the diodes are good, and match the part you indicated.

Now we get into something outside my area of expertise. The next logical step would be to hook everything together, hook the monitor to a working computer, and measure the voltages across some of the capacitors, particularly the ones with a very low resistance. Unfortunately, I have only a vague idea of what voltages to expect.

PlainBill

[killian6pk]

Re: Dell E207WFPc

I will try that and hope I don't fry myself or the monitor.

[killian6pk]

Re: Dell E207WFPc

I hooked everything up to start taking measurements. First of all I could not get either a DC or AC reading because the DMM kept jumping all over the place. Secondly the back of the TCon board in the area that I was taking measurements in got very very hot so I stopped and turned the power off.

[killian6pk]

Re: Dell E207WFPc

I did some more checking and the attached picture with the 2 red dots is the part getting so hot. It is marked as 3R3. Not sure what to call it to do any checking for a data sheet or anything else. It gets so hot in just a few seconds that you can't touch it. I did a search and this is what I came up with. Looks like the part to me. This parts measures to be the DR73-3R3-R

[PlainBill]

Re: Dell E207WFPc

I did some more checking and the attached picture with the 2 red dots is the part getting so hot. It is marked as 3R3. Not sure what to call it to do any checking for a data sheet or anything else. It gets so hot in just a few seconds that you can't touch it. I did a search and this is what I came up with. Looks like the part to me. This parts measures to be the DR73-3R3-R

That is an inductor; itm together with the square chip and the various diodes and caps you have been testing (plus a few more diodes) provides the various voltages the lcd panel requires.

I see two approaches at this time.

1. Remove the caps that showed an unusually low resistance and test them out of circuit. Maybe you will get lucky and find the culprit.

2. Cautiously feel the rest of the components and see if you can find any that are also getting quite hot.

What is the part number of the 'square 28 pin IC'?

PlainBill

[killian6pk]

Re: Dell E207WFPc

The part numbers are:
AAT1164C The "T" Could Possibly be an "F"
AG7879

I will check all the components for heat tomorrow before pulling the caps. When I test the caps out of circuit what am I looking for?

[PlainBill]

Re: Dell E207WFPc

The part numbers are:
AAT1164C The "T" Could Possibly be an "F"
AG7879

I will check all the components for heat tomorrow before pulling the caps. When I test the caps out of circuit what am I looking for?

You are looking for one with a low (around 75 ohms) resistance.

EDIT: I've attached a typical schematic for the power controller. I don't know how relevant this is, but it shows it produces 13.3V, 15V, and -6V. Rather than pulling caps, I'd check for those voltages.

PlainBill

[killian6pk]

Re: Dell E207WFPc

I will check these voltages out. Thanks for finding the data.

[killian6pk]

Re: Dell E207WFPc

I tried several of the pins for readings, but my DMM was jumping around so much I could not get a reading. The chip and the 3R3 component are both getting so hot you can't touch them with your finger and the same thing applies to the board even through to the back. Is this a short circuit or a bad component? Is one problem related to the other?