A user of a Dell Latitude D505 laptop was having a problem with the display periodically going blank. I noticed that the LEDs on the center control cover where the power button is located would also go out at the same time. Pressing hard on the center control cover near the power button in the area indicated on the picture below would restore the display and cause those LEDs to light again.
But, the problem might recur after pressure was removed from the area. Or, if it didn't, just typing on the keyboard would result in the problem recurring. Without using one hand to keep constant pressure on the area of the center control cover, it would be extremely aggravating to try to work on the laptop.
I dissasembled the laptop. At first, I thought the problem might be just a loose connection where the cable from the display attaches to the motherboard, as shown below. I reseated that connection, but that didn't have any impact on the problem.
Underneath the center control cover, there is small printed circuit board with a post on it which gets depressed when someone pushes on the power button. I found that pressing down on that board would restore the display and cause the 3 LEDs on it to come back on.
So I removed the two screws by which it is attached and attempted to disconnect it from the motherboard. There is a male connector on the bottom of the board that fits into a female connector on the motherboard. I expected those to separate when I pulled up on the small board. I was going to try reseating the connection. Instead, the connector attached to the motherboard came away with the connector on the underside of the board.
The diagram below shows the connector that separated from the motherboard and the spot where it was attached.
There are pins on the underside of the connector that was attached to the motherboard that come into contact with corresponding pins on the motherboard. There were two small metal tabs on either side of the connector that appeared to have been soldered to the motherboard to hold it in place. I tried resoldering the connector back in place a couple of times, but I couldn't even get the laptop to power on afterwards. Eventually one of the tabs fell off. Since the tabs seemed to be there just to hold the connector in place rather than for an electrical connection, I even tried super glue to hold the connector in place on the motherboard, but I could not get the laptop to power on again, though I would see an LED on the motherboard light briefly at times when I pushed the post for the power button.
I don't know if I wasn't getting the 20 pins on the underside of the connector aligned properly, though I made about 1/2 dozen attempts, removing and reattaching the connector to the motherboard. At thatp point I didn't think I was likely to be able to get the laptop working with the existing motherboard.
I think that the connector wasn't solidly attached to the motherboard when I began the process. Pressing down on the board directly beneath the power button would make the display and LEDs relight. Since that connector is directly under that area, I surmised that is where the problem lay, i.e. the problem was with the motherboard not the display itself, so I ordered a replacement motherboard through eBay.
Dell provides an HTML version of the service manual for this laptop that can be viewed online at Dell™ Latitude™ D505 Service Manual or from this website at Service Manual. A self-extracting zip file version can be downloaded from Dell's website at Service Manual or from this website at sm.exe.