DELL 3007 WPF blurry and slow

[dispera2]

Hello.

I recently got hands on a DELL 3007WPF with an unknown error. After I power it up, it runs through its full screen colour test cycle. The colour transitions appear very slow and blurry, including a few horizontal lines.

I created a youtube video to demonstrate the behaviour: click

Also, I connected the display to my pc and extended my desktop. The shown image was completely distorted. If I move my cursor, the display shows a vertical bar which reacts to my motion.

I tried to make full screen colour transitions, similar to the ones in the test cycle. A full-screen blue appears as orange, full-screen black as blurry white...

If required, I can create another video showing this.

I already replaced all caps on the power board.

I suspect the logic board to be faulty, but I don't want to invest in a spare part only to realise it's not.

My question is: Has anyone seen this behaviour before and knows where I should start looking?

Any advice is much appreciated.

Sorry for my "bumpy" english

Thanks.
-Frank

[Davi.p]

Re: DELL 3007 WPF blurry and slow

Hi, i'm not an expert but have seen an a bit similar symphtom on a very old acer lcd, that i don't have repaired, but i think the problem reseats on the tcon borard, so what do you think about take a picture of it and after make some measurements on it ?

[dispera2]

Re: DELL 3007 WPF blurry and slow

Hi Davi.p, thanks for your reply.

Here is a picture of the PCB:


Very well, I disassembled the display and powered it up while everything was connected.

I checked various control pads:

PWR_ON = 3.36V
VIN_18V = 17.7V
VCC = 3.37V
DVCC = 3.35V
AVCC = 3.37V
AVCC_25 = 2.59V
PS_ON = 3.37V
VDD = 15.2V ( IC "U7" generates VDD out of VIN_18V, depending on the used feedback resistors, 15.2V seems legit)

Seems ok so far.

Questionable are:
VGH = 1.94V
VGL = 0.87V
VCOM_IN = 0.97 (VCOM Buffer Input)

are those reasonable voltage levels?

I tried to find the IC responsible for VGH/VGL/VCOM but couldn't find it.
- U7 generates VCC and VDD
- U6 seems to be the VCOM Buffer
- U5 is a frequency generator
- U1 generates AVCC_25

I'm afraid UC1 is responsible for VGH/VGL/VCOM...

[Davi.p]

Re: DELL 3007 WPF blurry and slow

Hi, it seems too much complicated for me, but i've done some little research, from an other bigger (37") lcd tcon cross reference/schematic watch i see its values similar to your voltages apart from those 3 that you put in doubt, also from an "lcd bias power supply ic" datasheet i see that Vgl must be around -5/-6v and Vgh at 27-32v , also vcom seem to must stay at 5-6v, then try to test resistors/diodes around the VGL/VGH testpoints.. i add, U7 seems responsible for VGH/VGL, to know it test for continuity between its pins to C264 C245 C287 C288 (near VGL-VGH testpoints).. test also all caps connected to U7.. good luck...

[dispera2]

Re: DELL 3007 WPF blurry and slow

Hi Davi.p!

Just a little update:

I managed to get the display working again. I found a faulty ceramic-cap on the source PCB (connected by the ribbon cables), creating a 14Ohm resistance between VGH and GND. I replaced it and the display works fine for several weeks now.

Caused by the faulty cap, the display ran in a kind of emergency operation to prevent a permanent panel damage. This would explain the strange voltage levels of VGL.

Now:

VGH = 26.4V
VGL = -7.7V
VCOM_IN = 0.97

Cheers!

[selldoor]

Re: DELL 3007 WPF blurry and slow

That is great news - If you could find a picture of the board and mark the defective item
it may be a good help for others in future, or if you could remember the board part number
C??

[WhiteDesertSun]

Re: DELL 3007 WPF blurry and slow

Dispera, I'm curious if your monitor looked anything like mine when it was plugged in. I have very similar problem to yours, I think. I get some odd artifacts
http://i.imgur.com/wOvfwDF.jpg

[selldoor]

Re: DELL 3007 WPF blurry and slow

Whitedesertsun suggest you send him a PM its months since he visited and didnt even respond to my next day post.

[WhiteDesertSun]

Re: DELL 3007 WPF blurry and slow

selldoor I'm glad someone responded! Thanks. That was my plan but I figured I'd post in this thread seeing as forum rules need me to post before PM system unlocks

[dispera2]

Re: DELL 3007 WPF blurry and slow

Greetings.

Yes, I was not here for a while, sorry for the late answer.

@selldoor

I found my old notes. Unfortunately I did not take any pictures of the failing PCB.
What I can say is, that there are two similar "source" PCBs which are connected by the ribbon cables shown in the picture above.
On the left PCB, the ceramic capacitor C28 (10uF) failed and caused the error.

@WhiteDesertSun

The picture I got when I connected DVI was heavily distorted, much worse as in the example you posted.
I don't know your technical/electrical background (!) but if you are willing to give it a try, you can open the display. I would do the following:

-Check the caps for obvious damage.
-Power up the display while it's disassembled to check the voltage levels and compare them with the values I provided in this thread.

This might get you in the right direction for further investigation.

Regards,
dispera2

P.S. this could help to disassemble the display: click

[JMartinUSN]

Re: DELL 3007 WPF blurry and slow

I have 4.7 mv at AVCC_25, are you fairly certain that a voltage of 2.59 volts is required

[dispera2]

Re: DELL 3007 WPF blurry and slow

Hi Martin.

I'm pretty sure that AVCC_25 was 2.59V. Based on the name, I would expect something close to 2.5V.

Regarding your PM:

U1 should be the LDO generating AVCC_25.
Based on the picture, the manufacturer is "Analog Devices". Maybe you can find some kind of serial number on it. This would help to find a datasheet.

We have a pin one indicator at the upper left corner. Based on the adjacent
components i would assume: (Counter-clockwise, starting at pin 1)

Pin - Function
1 and 2 - V_OUT
3 - Feedback
4 - NC?
5 and 6 - GND
7 and 8 - VDD

R66, R67, R22 and R65 should be the feedback resistors. C115 and C85 stabilize the output voltage.

FL19 could be some kind of ferrite core to get rid of ripples on AVCC_25.

By the way, did you measure the input voltage at pin 7 and 8?

Long story short: I would remove FL19 first and repower the board. Check if U1 generates ~2.5V.
If yes, the error is after FL19, maybe a ceramic capacitors that is following.
If no, check everything around the LDO (U1).

Regards,
Frank