"Jeff Liebermann" wrote in message
...
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.
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.
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.
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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First, the water ran in the hole as liquid but you are trying to get it back
out as vapor which is going to be a much slower process. There is about a
1000 fold expansion in volume going from liquid to vapor, and the flow
conductance of the hole will be 2-10 times lower for vapor depending on the
pressure (for this case, using a pump with the liquid would be cheating
:-)). Second, depending on the size of the hole and the mass of the glass
at the hole and how much water there is and where the boiling and thus
evaporative cooling is occurring and lots of other things it is entirely
possible for the water to freeze as it boils inside the hole so the ice can
plug the hole. This stops the drying and the evaporative cooling as the ice
slowly warms back up by conduction from the mass of the LCD, melting the
ice, so it can boil again, then freeze and plug the hole, and round and
round it goes. The vacuum is also an insulator so the LCD will slowly cool
down and each melting cycle will be slower - venting to atmosphere every so
often can actually speed things up sometimes. With one tiny pinhole this
probably isn't an issue but if you are trying to dry something bulky like a
book a heat lamp and venting to melt the ice block occasionally really
helps. Of course, that assumes you aren't freeze drying something fragile
like a drug where you need the frozen matrix to prevent chemical damage.
Anyway, I think vacuum would work but it will be very slow. The
descriptions I've heard using dry rice talk to dry a wet cell phone talk
about a few days, and I bet the vacuum wouldn't be much faster to dry an
LCD.
--
Regards,
Carl Ijames