Dell 2408WFPb: multicolour vertical stripes

[HAHOMETP]

Folks,

I have a Dell 2408WFPb with a defective T-Con board (determined by swapping parts with the known good 2408WFPb). I touched up each and every soldered pad on this board with my Weller pencil, but the problem is still here. I also tested the fuse F1 as well as all of the 0 ohm resistors and every p-n junction on the board except for the 5 chips. Which part might be causing this condition?

Please see the attached pix of my good 2408WFPb with the T-Con board lifted off the bad 2408WFPb.

[budm]

Re: Dell 2408WFPb: multicolour vertical stripes

Did you check the Voltages on all 3-pin Voltage regulators? There are 4 (U7, 9, 19, 21) of them, and since you do have working board then you can do the comparison readings.

[HAHOMETP]

Re: Dell 2408WFPb: multicolour vertical stripes

All four voltage regulators are LD1117 by ST Microelectronics. According to the datasheet they come in several output voltages (1.2V, 1.8V, 2.5V, 2.85V, 3.0V, 3.3V and 5.0V).

Here are their actual output voltages as measured on Pin2:
IC7 (marked LD1117): 2.51v
IC9 (marked LD1117): 2.52v
IC19 (marked LD18): 1.81v
IC21 (marked LD33): 3.31v

[budm]

Re: Dell 2408WFPb: multicolour vertical stripes

IC7 and IC9 are adjustable 1117. Can you please verify the Voltage between pin 1 (ADJ) and pin 2 (output), it should be 1.25V.
IC19 (1.8V REG), 21 (3.3V reg) are fixed outputs.

[HAHOMETP]

Re: Dell 2408WFPb: multicolour vertical stripes

budm,

you're right as always. I overlooked that they were adjustable. I am wondering why Dell did not use the 2.5v fixed ones instead. Anyway, they both check out.

IC7: 1.269v on Pin1
IC9: 1.274v on Pin1

[HAHOMETP]

Re: Dell 2408WFPb: multicolour vertical stripes

Also, the previous owner stated "Monitor turns on and displays an image but has the blocks on the screen that overlay (see image). The blocks used to go away once the monitor was warmed up but now they are there all the time. "

Attached are the pictures that were provided by him. If he is telling the truth the problem has progressed from the intermittent boxes on the cold monitor to the permanent stripes that I am seeing. I left the monitor on overnight but the stripes did not go away.

[justanothercanuck]

Re: Dell 2408WFPb: multicolour vertical stripes

I once had a Dell laptop that displayed this issue (or something similar), it turns out it was a panel fault. If I recall correctly, the individual lines on the vertical would just choke and get stuck on a single colour, or flicker between a handful of colours. Happened to a whole bunch of them about 10 years ago. Was covered under a grandfathered warranty, but the laptop was too old for me to care at that point.

[Agent24]

Re: Dell 2408WFPb: multicolour vertical stripes

Did those 2 big chips on the board have heatsinks? Because it looks like they did but no longer do...

[HAHOMETP]

Re: Dell 2408WFPb: multicolour vertical stripes

The whole T-Con board is covered with a thin steel shield. There are two square pieces of rubber like material about 3mm thick on its inner surface. They get tightly pressed up against the two large chips when the shield cover is secured to the board with 4 screws on the perimeter. Quite possibly these two pieces are indeed some heat sinks of sorts. I need to figure out how to spray the T-Con board with compressed air to freeze it and see if the stripes disappear. For that I need to relocate the power supply board mounted above the T-Con board.

[HAHOMETP]

Re: Dell 2408WFPb: multicolour vertical stripes

I once had a Dell laptop that displayed this issue (or something similar), it turns out it was a panel fault. If I recall correctly, the individual lines on the vertical would just choke and get stuck on a single colour, or flicker between a handful of colours. Happened to a whole bunch of them about 10 years ago. Was covered under a grandfathered warranty, but the laptop was too old for me to care at that point.

In my case the T-Con board is most definitely at fault. I swapped the T-Cons between the two identical 2408WFPb Dells and the problem migrated from one monitor to another.

[HAHOMETP]

Re: Dell 2408WFPb: multicolour vertical stripes

The T-Con boards for Dells 2408WFPb (LTM240CS05FFCC4LV0.4) and 2407WFPb (LTM240M2C4LV2.4) are almost identical and the connectors are the same and are located in the same places.

Does anyone know if are interchangeable?

[Agent24]

Re: Dell 2408WFPb: multicolour vertical stripes

No idea. Compare schematics?

[HAHOMETP]

Re: Dell 2408WFPb: multicolour vertical stripes

I wish I had them...

[dragos2009]

Re: Dell 2408WFPb: multicolour vertical stripes

the first one has a connector on left and the other one doesn't have that connector and even the main chip and panel connector are different

[HAHOMETP]

Re: Dell 2408WFPb: multicolour vertical stripes

Good catch RE: connector on left. I missed it. Thanks!

[HAHOMETP]

Re: Dell 2408WFPb: multicolour vertical stripes

An update. A used T-Con board off ebay (20 bux delivered) has fixed the issue.

[Agent24]

Re: Dell 2408WFPb: multicolour vertical stripes

Nice!

[Achim64Germany]

Re: Dell 2408WFPb: multicolour vertical stripes

Hello Friends,iam from Germany and my english is not so good sorry.Iam new here and iam a hobbyist Tech.
Please i need help for my Dell 2408.First there is a Diode wrong (broken) on the Powerboard.What Diode i need for repair?
Thank you Achim

[budm]

Re: Dell 2408WFPb: multicolour vertical stripes

Please upload good clear pictures of YOUR boards and point out which Diode is broken.

http://s807.photobucket.com/user/bud...?sort=3&page=1

[Achim64Germany]

Re: Dell 2408WFPb: multicolour vertical stripes

http://img4.fotos-hochladen.net/thum...rxyo_thumb.jpg