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Posted to sci.electronics.repair,sci.electronics.design
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Saving LCD screens that were under water
On 6/7/2018 9:24 AM, Jeff Liebermann wrote:
On Thu, 07 Jun 2018 00:15:38 -0500, wrote:
I had some electronics in a storage building, which flooded. I figured
that most of it is junk, but I wiped it clean and put some of the stuff
outside in the sun to bake dry. So far, much of it works. But two
items, a GPS and a Police Scanner, both with LCD screens have very faint
screens. I kind of think the water affected the LCD screens.
Is there any way to get them LCD screens to work (other than replacing
them)?
No. LCD panels are not hermitically sealed. If it were sealed, the
glass would bulge when the panel becomes hot. There is a tiny hole,
usually near the bottom of the screen, to equalize the air pressure on
both sides of the glass. If you immerse the panel in cold water, the
air inside the glass screen will contract, causing a partial vacuum,
which will suck the water into the panel. If you remove the frame
from the panel, you can see the water inside the panel.
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.
Even if it did get the water out, the LCD still might not work.
Best results were to attach something
that wicks water (cotton balls, rice, desiccant) at the hole, to suck
out the water via capillary action. Even so, I was only able to
extract a tiny amount of water, leaving most of it inside the panel.
When the price of panels dropped dramatically, I gave up on trying to
fix these.
The GPS and radio scanner probably have corrosion damaged PCB traces.
If you can find the damage and repair the traces, both can be fixed.
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