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Hewlett-Packard began manufacturing personal laptop computers in 1993.

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LCD not working right

Ok so I admit this is my fault, I bought a laptop as a back-up and it had wifi troubles so I was adding another wire antenna to see if it boosts the signal etc which it did but I had some wire sticking out of the corner of the lcd.
My wifes laptops lcd is kinda messed up so while I was removing the screens panel to hide the wire I thought I would see if the lcd has the same connect as my wifes, so I took the lcd out to compare them.

They had different pins so I put the lcd back in the hp laptop and when I came to switch it on the screen was not working.
I can get a picture on an external monitor and the lcd is not black, you can tell it is displaying something as when I put a white page on full screen you can see the lcd change.

I do not understand how simply removing the cable for 5 minutes then plugging it back in would break anything. The laptop was not powered up and had no battery in it.

I have checked to make sure the cable is all the way in on both ends and yes I was kinda mad at this point as I am having multiple laptop problems so after it first was not displaying much I did have the “F%^^&” it attitude and unplugged it while it was on but that was after it already was buggered.

So in short…..
I removed the lcd for 5 minutes then put it back and now it doesnt work.

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Hi,

What is the model number of the laptop?

Also what is the make and model number of the motherboard as printed on the board itself?

You may need the schematics as it sounds as though you've damaged the LCD panel's backlight power supply somehow or how the backlights are enabled

With the laptop turned on and booted up, try shining a torch at an angle close to the screen and check for any images. They will be very faint if they are there so trying this in a darkened room may help to see them.

If you can see them then depending on whether the LVDS cable has 30 pins or 40 pins, then usually the BL power is on pins 27-29 or 37-39 but not always.

If you have a DMM (digital multimeter) with the laptop turned on check those pins for voltage.

If there is no voltage then there's a problem with the power supply for the backlights. Depending on the motherboard circuit sometimes there is a fuse and sometimes not. If there is one it will be close to the LVDS cable connector on the motherboard. Look for a component with an "F" designation and test it for continuity.

If there is voltage there then there may be a problem with the backlight enable lead (BL_EN). The LVDS pin for this lead can vary so the schematics will be needed to find out which one it is.

This lead is used to signal the panel to turn the backlights on or off. There should always be BL power going to the panel.

It here is no BL voltage or even if there is here’s a link that may help with the schematics. Type the motherboard model info in the search box at the top right to hopefully get results. If none then search online for them with the motherboard information e.g. (insert motherboard make and model info) schematics

Update (09/23/2021)

Hi

Can you detect images using a torch in the dark sections of the screen?

Have you checked the LCD panel end cable connections?

Here’s the maintenance and service guide for the laptop, taken from this support webpage. This details how to access the LCD panel unit, so that you can check.

Here’s an image taken from the schematics for the motherboard showing the backlight power and enable pins on the LVDS cable connector. Apologies about the pin numbers before, as I said usually they are on the pins I mentioned, but not in this case. It always pays to have the schematics ;-)

Block Image

(click on image to enlarge)

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Hi there and thx for a reply.

The model is HP G094sa the motherboard zs051 LA-A996P.

I do not think it is the backlight as the screen is not black and rather hard to describe but I will have a go....

I can change the brightness using the fn keys and even though there is no clear image the screen is showing area's that is obviously the desktop, when booting up which is normally dark the screen is dark and when it boots to windows the screen shows an area that is now light and if I change the background the distortion changes. Its like the image signal is not reaching the lcd.

Like I said it is so strange that unplugging it for 5 minutes has damaged something.

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Sorry for the delay, I was assuming an email would tell me if another comment was added.

No imagine when shinning a torch, like I said I don't think it's a backlight problem.

All connectors are in fully and ordered a new cable since they are the cheapest thing to start with.

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@longpod99

So no images when in BIOS either?

Do you have to press the F4 key for an external monitor to display or does it display without it being pressed?

If it displays without needing to press F4 (or even if not) do a power refresh to restore the BIOS back to default settings.

Remove charger if connected, remove main battery, press and hold laptop Power button for a full 30 seconds then release. Reinsert main battery, connect charger and turn on.

If still no good repeat but this time remove coin cell RTC battery from motherboard as well, before pressing the Power button etc. See p.64 of the HMM for details about the RTC battery.

To get an email about responses, check your ifixit account details (click on your USER ID avatar > About > Edit check if your email address is there also check the Preferences tab.

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