Agilent E4433B - odd screen problem, ever seen this before?

[Tracker]

HI folks,
Have you ever come across this problem in an LCD display?
It's on an Agilent E4433B sig gen.
It looks like some form of decay within the LCD itself.
I actually think its been growing slowly over time!!!

Any advice?

Thanks


 

[iRepairElectronics]

  The fact that its orange is odd.  i work on LCD monitors that go out on rental alot. have had some with dirt come back, sandwiched in between the film of the panel.
would recommend taking out the lcd panel and see if can carefully pull the panel apart. Assuming of course its out of warranty.

[Tracker]

Oh yeah its well outa warranty!, Firmware is dated 1998.

Yes I had considered opening it up but just wanted to post it here in case anyone could identify the source and perhaps have a magic solution.

Ive added another wider view image to put it in context with the LCD.
I wonder if it could be fluid leakage between the LCD layers?
Its a bit 'crystal like' in nature dont you think?

I usually find that I'm never the first to discover something !

Cheers
Ray

[nctnico]

I've seen bad spots in LCD (more specifically TFT screens) before. Tracker PMed me to point me to this thread. My E4421B had a faulty LCD display and that showed a yellow rectangle. This looks more like damage due to aging. Maybe the display has been used on bright sunlight or so.

[Armadillo]

I am thinking, either is the backlight is ageing or the Light reflective White plastic backing behind the LCD has discolored.

[Tracker]

Thanks guys,
This unit was stored in an un-heated warehouse for several years, it was bagged and boxed but I suspect it was exposed to low-ish temperatures as low as +3 or +5, but probably not below freezing. (Ireland rarely experiances sub-zero temps for long)..
I'm planning to open it up and inspect the LCD, but I suspect the display is a sealed unit and can't be torn appart??
 
what do you think?

Tracker

[nctnico]

You can take the display apart but I doubt the problem is in the backlight. Can you make a close-up of the problem area? If the problem affects pixel size portions then it is likely the LCD itself which is deteriorating.

[Tracker]

Ok, some images below.

the closest i can get with my phone and stay focused.
it's not pixle mapping, it's covering parts of pixles in some cases...

I also notice that the 'stain' remains unchanged over the full range of contrast, i.e. from bright to very dark. The stain keeps the same intensity.
Also, when the unit is powered off i can just about make out the stain with a bright torch.
It seems to be on the very front surface or at least very close to the front.

[Armadillo]

Ingress of moisture, fungi growth..... looks like.

Better wear protective gloves and mask....

[Tracker]

Ingress of moisture, fungi growth..... looks like.

Better wear protective gloves and mask....

Yeah I think so!
If its letting the backlight pass through then I think it may have already damaged the polaroid layer 

[Armadillo]

The fungi seems to be on the housing front glass panel or front of the LCD. Should be cleanable.
Only the yellow stain, I think reflective backing white plastic is stained.
Well, have got to open up to check. Not cheap for a new LCD.

[Tracker]

That's a job for tomorrow evening.
Thanks for the advice folks.
I'll update here with my findings.

Cheers
Tracker

[Tracker]

So I owe you guys an update on this one.

I opened her up and examined the LCD display up close.
Unfortunitely the 'thing' is sandwitched in the LCD glass itself.
It's not a fungus because the glass is completely sealed, but it's some form of  degregation withing internal layres of the LCD itself.

Here is a photo of the LCD held up to a light.

Further disassembly isnt possible, the LCD appears to be one tightly sanwitched glass sheet.

Its a pity because the instrument is perfect otherwise.

My suspecion is that this was caused by a particulatly cold winter we had sevral years back and the generator was in an unheated warehouse at the time.
So as long as I keep it in relative normal storage conditions it shouldnt get any worse.

Thanks for your assistance fellas!

[free_electron]

this looks like some crystalline growth ....

[Tracker]

Yes thats probably a good description.

I'm sure the makers of LCD know what causes it, i can only guess.