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mike[_22_] mike[_22_] is offline
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Default Saving LCD screens that were under water

On 6/7/2018 4:32 PM, Jeff Liebermann wrote:
On Thu, 07 Jun 2018 13:15:07 -0700, mike wrote:

On 6/7/2018 9:24 AM, Jeff Liebermann wrote:
(...)
I had the bright idea of heating the panel to build up internal air
pressure and thus push the water out of the panel. That didn't work.
I also tried using a vacuum pump on the outside to help suck out the
water, but that also failed.


I'm surprised that the vacuum failed. Should pump down to the vapor
pressure of water and hang there until the water is gone before continuing
the pressure descent. That's as dry as you're ever gonna get it.


I agree. It should have worked. I still have all the equipment
(except the fish tank) and could probably try again. I see water and
chemical cleaner damaged laptop displays all the time. They usually
have a jagged area near the bottom of the screen that has turned dark
black and shows no image. Most of the damage comes from spray
cleaners used to clean the LCD display, where the cleaner or water was
allowed to run down the screen, under the bezel, and into the display.


In that case, I don't think there's anything you can do to fix it.
Once the water has invaded the pixel area, it's all over.

I was using an Edwards E2M-1.0 2 stage rotary vacuum pump:
https://shop.edwardsvacuum.com/products/r1/list.aspx
It's been run well past its 30,000(?) hr major overhaul point and is
probably leaking around all the rubber vanes and seals. As I recall,
it went down to about 200 milliTorr and refused to go lower, probably
because of leaks in the reinforced fish aquarium I was using for a
test chamber. Water has a vapor pressure of 25 Torr (0.5 PSI), so
that should have easily sucked all the gas and water vapor out even
with all the leaks. I had hoped to see some boiling near the hole,
but didn't see any.


I was experimenting with making heat pipes years ago. I don't remember
the numbers, but 0.5 PSI sounds WAY higher than I was trying.
As a test, I put the vacuum gauge right on the suction port of the pump.
It went down to where water was supposed to vaporize and stuck there
until I gave up. Reading about it suggested that you have to suck all
the water (and other contaminants) out of the pump oil before you can do
anything useful. They recommended FRESH oil for every evacuation.
I bought some pump oil, but never got around to trying it.

What I think might have happened is the air pressure equalization hole
got plugged up with a RTV used to seal the glass panel. The pressure
on the parallel glass plates might have compressed the RTV seal, which
then expanded sideways and closed the hole. Just a guess(tm).

Even if it did get the water out, the LCD still might not work.


Yes, but it was worth the risk. At the time, large LCD panels were
rather expensive. However, when I put everything back together, I
still had a 1/4" wide jagged black smear at the bottom of the screen
near both corners.

Incidentally, my "fix" for this customer was rather creative. I
flipped the monitor over by reversing the position on the VESA mount
and inverted the display using the Nvidia display control application.
It then had black areas near the top of the display, where there's
very little worth seeing. However, the customer could now see the
bottom of the screen, where the task bar and Start button reside.
Moving just the task bar to the top of the screen didn't work, because
the Start button was under the black blob and couldn't be seen.