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Posted by mike on February 3, 2008, 9:34 pm
Please log in for more thread options Quaoar wrote:
> stickware@gmail.com wrote:
>>>
>>> stickw...@gmail.com typed on Sun, 3 Feb 2008 16:58:50 -0800 (PST):
>>>
>>>> Hi. I have a HP ze5385us laptop that I was doing a repair to the DC
>>>> jack. I fixed the jack and I was letting it charge up while the LCD
>>>> display was not yet attached, then I mistakenly plugged the display in
>>>> to the motherboard while everything we plugged in.
>>>> I am guessing that is why when I got it all together the display is
>>>> not working. It turns on bright when the laptop is powered on, but
>>>> nothing is being displayed. The brightness controls dim it, but still
>>>> nothing on screen. When plugged to an external monitor, it displayes
>>>> properly there.
>>>> Did I fry the diplay? What do you think I need? What exactly is an
>>>> inverter?.....thanks in advance.
>>> Oh no Dave! You were doing well until you know what. :( But you didn't
>>> mention what happens when you plug it into an external monitor (you have
>>> to activate it usually with the Fn key and something else key). Anyway
>>> it doesn't sound good. :(
>>>
>>> An inverter supplies high voltage (like a thousand volts) to the
>>> florescent lamp. If you can't see anything on the screen except
>>> something really white or in very bright light, but the screen is still
>>> very dark. It's the inverter that supplies the high voltage to the lamp
>>> or the lamp itself like 99% of the time. But that isn't your problem.
>>> The lamp is what makes everything bright on the screen. Without it, only
>>> an external bright light will show anything on the screen and not very
>>> well.
>>>
>>> --
>>> Bill
>>> email: change kom to com
>>
>> Thanks for your help. When I plug in an external monitor, the
>> external monitor works, verifying that the laptop is working properly.
>>
>> So are you saying my problem isn't the inverter? I am confused. I
>> see just a bright light, but no images from the computer. So what does
>> that mean? Is the lamp replaceable if I need that?
>>
>> Thanks
>> Dave
>
> It means that, for some reason, no video signal is being received by the
> LCD. It might mean that the ground strap is not connected to the frame,
> or the video cable is broken, or the video cable is not properly
> inserted into the mainboard socket. ...or something else having to do
> with the video signal to the LCD.
>
> Q
If you have light, it's not the bulb or the inverter.
I bet you fried something when you plugged it in hot.
My (yours actually) money is on fried display controller on the
motherboard. You can still have external vga and fried lcd drivers.
Different parts of the chip. Made one work once by adding a pullup
resistor to replace the fried pullup fet on the output pin.
But it could still be bad cable or lcd.
Don't overlook the obvious. I've seen screws, pieces of the aluminum tape
used for shielding etc wedged under the circuit board shorting stuff
out. Bent pins shorting. Tiny chips ripped off the board while prying
stuff apart. Tiny pieces of metal can flake off where the self-tapping
screws were. Fall down and short tiny chip pins.
Laptops are like a Chinese jigsaw puzzle. Put together in the wrong
order and stuff gets bent so it don't work. Wrong length screw can short.
Lots of possibilities, but my money is on the video chip. If it's marked
and you can find a datasheet and you have a scope, you can go looking
for signals on it.
mike
--
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