When the cover of my Samsung is slide up the screen works well, but when I slide it down, the image disappears, tough the phone is still on, but no image at all.

Check to see if there is some way to reset the phone electronics. Otherwise you are SOL!

the flexes probably had been damaged by now, stratosphere is not that tough when it comes to water, unlike galaxy s3, you need a technician now for your phone to work, or better yet, look for the nearest samsung service center and bring your phone there.

That has got to be a flex problem with your phone.the flex connects the movable parts of your phone. you will have to see a certified engineer to fix a new flex for your phone.thanks

samsung u700 main camara on why display please slide up

I think this a problem related to the flex cable that connects the main phone body to the sliding screen. Over time the flex cable wears down as it slides and results in a whole range or problems such as: display acting weird (eg. mirror-image and inverted colours), speaker not working, off-button not working etc.
Flex cables are cheap to buy on ebay (a few dollars) and there's internet sites that show you how to open the phone and replace them. (google: samsung u700 replacement flex cable)

On the back of the phone bottom half, push down where it meets the top half and at the same time push (slide) it down away from the top half. It's very tough but it will work.

I think this a problem related to the flex cable that connects the main phone body to the sliding screen. Over time the flex cable wears down as it slides and results in a whole range or problems such as: display acting weird (eg. mirror-image and inverted colours), speaker not working, off-button not working etc.
Flex cables are cheap to buy on ebay (a few dollars) and there's internet sites that show you how to open the phone and replace them. (google: samsung u700 replacement flex cable)

Thats not completely true, it is easier to replace just the top half of the phone but you can replace only the LCD. The repair will probably need to be done by somebody who has some experience doing this becaus it can be rather tedious. But it is possible.

hi reckon you have a faulty ribbon cable replace and it should be ok thats if a software flash doesnt sovle ya problemas lylo recommends mrjazon