HP 6720s Display switch mystery

dodger46

Distinguished
Nov 19, 2011
110
0
18,660
10
Removed switch cover and keyboard to clean dust from fan, but on re-assembly no display. Noticed I'd disturbed the Display Switch Assembly, re-seated it, still no joy. Obtained a replacement in case it was damaged, same result. Problem is I can't see for the life of me how it actually switches anything! There doesn't appear to be anything on the hinge assembly that affects the switch assembly in any way. As far as I know nothing has dropped off. Below screenshots of Hinge assy and Sw Assy.
Can anyone throw any light on the subject?







I don't see any moving parts on the Sw assy, no switches at all!
 

bucknutty

Distinguished
Jul 22, 2010
60
0
18,610
5
Sometimes they are magnetic. Is there a magnet or a chuck of metal in a corrisponding location on the screen. So when you close the laptop the magnet triggers the switch and it goes to sleep?
 

dodger46

Distinguished
Nov 19, 2011
110
0
18,660
10

Cable sits quite happily in the slot, and the cct board won't fit any other way in the bracket. As for the operation i wondered if there is a magnet in the hinge which triggers something in the switch mechanism when the lid is shut. Doesn't explain loss of display with lid open, though...
 

dodger46

Distinguished
Nov 19, 2011
110
0
18,660
10
Seems it is magnetically operated, there is a magnet under the bezel above the hinge cover. Either I have two duff switches, or the GPU has finally died due to the laptop overheating when a lump of dust jammed the fan blades....
 

dodger46

Distinguished
Nov 19, 2011
110
0
18,660
10

Have the manual thanks all the same. I've had a few of these through my hands, nice 'tops if a bit dated now. Looks like I'll have to strip for spares, annoying as I just bought a new k'brd and switch panel as the originals were a bit rough!
 

getochkn

Splendid
Moderator
Does display work through an external monitor? Can you press the switch and turn it on?

If all those don't work, does it have an Nvidia chipset or Graphics in it? HP's and Nvidia has a huge problem with lead-free solder and their chips, so much so, there was a class action lawsuit against it.
 

dodger46

Distinguished
Nov 19, 2011
110
0
18,660
10

Tried an external, no joy. It's all Intel, so I'm a bit surprised that the GPU wouild fail, especially as it was turning itself off after a few minutes according to the owner. Should I spend another £3.50 on another switch...
 

bucknutty

Distinguished
Jul 22, 2010
60
0
18,610
5
Could you have messed the power inverter for the LCD? They die pretty often. Try plugging in a normal computer monitor to the vga and see if you get anything. That would show you that the computer is working and the issue is with the display.
If the regular computer monitor works, then chances are the inverter is bad.
 

dodger46

Distinguished
Nov 19, 2011
110
0
18,660
10


Tried that, blank screen, so it's either the lid switch or the GPU.
 
Thread starter Similar threads Forum Replies Date
slepong Laptop Tech Support 0
S Laptop Tech Support 0
P Laptop Tech Support 2
Galvan1 Laptop Tech Support 0
A Laptop Tech Support 1
Semilore kaj Laptop Tech Support 0
G Laptop Tech Support 0
A Laptop Tech Support 0
S Laptop Tech Support 0
B Laptop Tech Support 0
D Laptop Tech Support 0
N Laptop Tech Support 0
R Laptop Tech Support 5
celal2344 Laptop Tech Support 2
E Laptop Tech Support 0
S Laptop Tech Support 2
Wahab Chattha Laptop Tech Support 0
powerman4u Laptop Tech Support 7
Hywther Laptop Tech Support 1
V Laptop Tech Support 2

ASK THE COMMUNITY