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)?
The least bad way is to rewash in distilled water with no power and let them dry again. LCD contrast can be ruined by any leakage pin to pin.
Drying further by putting the unit in a sealed jar with rice once you have naked it dry in the sun (or in a real dessicator is also helpful).
Some things just don't recover from being dropped in dirty water - my previous dumb mobile phone for instance. It was bricked by that.
-- Regards, Martin Brown
Must not of needed it or it wouldn't have been in a Storage building.
Throw the stuff out and spend your time fixing the roof.
-- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com
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. 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.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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
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: 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).
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 jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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: 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).
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 snipped-for-privacy@cruzio.com
150 Felker St #DFirst, 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
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 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.
Yep. The secret to engineering is knowing when to give up.
Vapor pressure of water in Torr: and in PSI:
25 Torr or 0.5 PSI look right.That could have been my problem. At the time, all I had was the oil that was in the vacuum pump when I bought it used. It probably was rather dirty and likely contaminated with some water from condensation. Looking at the pump through the oil level sight glass, it looks dirty. New oil is about $30/gallon. I was eventually going to buy the o-ring and basic rebuild kit, at which time I would buy some new oil. However, I was getting a usable vacuum, so I didn't bother.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
If my google is right, HVAC systems are typically evacuated below
500 microns to get all the water out. That's more like 0.5 Torr. My memory is vague, but somewhere under 2000 microns was where the pressure stopped decreasing due to water contamination. With even the slightest leak in the system, I couldn't get there.
The point at which water starts to boil at room temp is 20,300 microns of Hg or 0.393 PSIA or about 20 Torr. Presumably, that's when the water starts to turn to vapor which can the be removed by the pump. However, at this pressure, it will take forever, so a much lower vacuum is probably more practical. Whether it needs 40x more, I don't know.
When I filled my aquarium with water, applied a vacuum, and looked for bubbles, in order to check for leaks, I found quite a few. These were duly plugged with RTV. I had no trouble going down to what I thought was 200 milliTorr (0.00386 PSI), but now I'm not so sure. I have the vacuum pump and gauge and might be able to try again, but not for a while. I would need to build a new vacuum test chamber and don't have the time, bench space, fresh vacuum oil, fittings, rebuild kit, etc.
-- Jeff Liebermann jeffl@cruzio.com 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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