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black screen HP Compaq Presario f700

This is a discussion on black screen HP Compaq Presario f700 within the Laptop Support forums, part of the Tech Support Forum category. Greetings, I have a HP Compaq Presario f700. The screen went black suddenly, not gradually. Works fine when plugged into


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Old 01-04-2011, 10:57 PM   #1
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Greetings,
I have a HP Compaq Presario f700. The screen went black suddenly, not gradually. Works fine when plugged into an external monitor so am assuming that it is not the motherboard, hard drive, RAM, or battery. The boot menu will not come up either. I have installed a new inverter board, but still a black screen. Wondering what is my next step, changing LCD screen? I thought if it was a backlight problem then it would have went out gradually, not suddenly. Any ideas would be greatly appreciated, thanks

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Old 01-05-2011, 12:28 AM   #2
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Hello budman2 and welcome to TSF,

The backlight can go out suddenly. Take a flashlight and shine it into the LCD panel... put it right up against the screen shining in to it... You should generate enough light to see the image... The backlamp is integrated into the display and connects to the inverter via a two prong plug... make sure that plug is inserted correctly and fully seated.

If you have access to another laptop or laptop screen, you can use it to test your inverter and your backlamp. But you will have to disassemble the second laptop.

There is a good chance the backlamp has failed but, due to the expense of LCD panels, I would try to test it out first.

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Old 01-05-2011, 09:20 AM   #3
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Thanks so much for your prompt response. I have shined a flashlight into the LCD panel and do not see any icons or images. I have a Toshiba Satellite laptop and was going to try the inverter test but was not sure if it was compatable as it is a different model. Can I still use it to perform the test? If I can't see the images with a flashlight, but the laptop works through an external monitor, what could this mean for me?
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Old 01-05-2011, 09:59 AM   #4
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Hi try the screen at slightly different positions (angles) with the flashlight and wait for GZ to get back to you
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Old 01-05-2011, 10:19 AM   #5
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Quote:
Originally Posted by budman2 View Post
Thanks so much for your prompt response. I have shined a flashlight into the LCD panel and do not see any icons or images. I have a Toshiba Satellite laptop and was going to try the inverter test but was not sure if it was compatable as it is a different model. Can I still use it to perform the test? If I can't see the images with a flashlight, but the laptop works through an external monitor, what could this mean for me?
Thx
You can... but not as easily as moving the inverter.

You will need to remove the entire display and connect it to the Toshiba's inverter. The backlamps plug will be the same but the input side of the inverter will not match.

Also, Double check all of your cable connections to the display.
Were you connected to the external display when you shone the light into the LCD?
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Old 01-05-2011, 12:28 PM   #6
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Hi GZ. I'm back, and thx! I used the flashlight without the external monitor first and saw nothing no matter how I angled the light. (doesn't work with the ex. mon. either of course) I hooked the Compaq inverter to the Toshiba screen and got nothing on the Toshiba screen. Then I hooked the Toshiba inverter to the Compaq and the screen came on but completely white. I am now more puzzled than I was. I hooked the Compaq back into the external monitor and it works fine. Since the screen went all white when I hooked up the Toshiba, I would have to guess that the backlight on the Compaq is OK. The inverter in the Compaq is brand new (or so I hope as I bought it on line) so it should be OK even though it would not feed the Toshiba. If there is a problem with any of the inner works of the Compaq, why would it work fine on the external monitor?
I guess it's possible that I now have 2 bad inverters, what do you think?
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Old 01-05-2011, 12:42 PM   #7
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Quote:
Originally Posted by budman2 View Post
Hi GZ. I'm back, and thx! I used the flashlight without the external monitor first and saw nothing no matter how I angled the light. (doesn't work with the ex. mon. either of course) I hooked the Compaq inverter to the Toshiba screen and got nothing on the Toshiba screen. Then I hooked the Toshiba inverter to the Compaq and the screen came on but completely white. I am now more puzzled than I was. I hooked the Compaq back into the external monitor and it works fine. Since the screen went all white when I hooked up the Toshiba, I would have to guess that the backlight on the Compaq is OK. The inverter in the Compaq is brand new (or so I hope as I bought it on line) so it should be OK even though it would not feed the Toshiba. If there is a problem with any of the inner works of the Compaq, why would it work fine on the external monitor?
I guess it's possible that I now have 2 bad inverters, what do you think?
I would suspect the inverter is not working properly if it failed to light two known good CCFL backlamps. I would contact the reseller to make sure you have the correct inverter for your Compaq and see if he will replace the one you recieved.

Also... the LVDS cable connections (the connection to the LCD panel itself) should be the same for both laptops. You can test for full functionality of the Compaq's display.
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Old 01-05-2011, 01:22 PM   #8
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GZ, I have sent a message to the supplier, thx. The inverters look almost identical, but as I take a real close look, there are some very slight differences, and the numbers don't match. Hope to get it resolved and will let u know. Your the best!
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Old 01-06-2011, 10:43 AM   #9
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Good day,
Still have not gotten a response from the seller on this inverter, however I did look up compatible models. I am replacing a AS0231720D2 and was sent a AS023172531 which is on the compatible list. It could still be defective. When I was installing it, I experienced a small bit of static electricity. Wondering if this could have affected it, and if not the inverter where would I look next. Thx
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Old 01-06-2011, 10:51 AM   #10
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Did you test the LCD for full functionality (display as well as backlight)?

If that is the case the next step would be the cable that connects the inverter to the motherboard. In some laptops this is a separate cable, but I am certain yours is part of the display cable.

You will need to make sure that it is properly seated into the motherboard.
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Old 02-26-2011, 12:29 PM   #11
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hey budman i think i know what your problem is. its the faulty nvidia chipset for the gpu. i had the same problem with my sisters and found this and it worked perfect.let me know if this helps ok?

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Old 02-26-2011, 12:31 PM   #12
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oh and i know it isnt the same model but the problem is the same and it worked on my sis f700. good luck man.
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Old 06-21-2011, 02:00 AM   #13
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Was this issue ever solved? I have the same Compaq presario F700 and I have the same issue. I notice that the back light comes on for literally 1 second then turns off quick. Do I need to replace my inverter board?
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Old 08-15-2011, 07:00 PM   #14
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I am also very interested to find out about the issue of this problem.

I have a similar problem and I do see the back of the screen with the proper angle and light (I have a PresarioF700O. And it works fine with an external monitor. But I just ain't sure about which part to change and if it's even worth it.
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Old 08-16-2011, 11:11 AM   #15
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Well, other than getting fairly familiar with the workings of the laptop HP Presario F700) I have not completely fixed this laptop. At first I was getting nothing on the screen even with the flashlight. I hooked to an external monitor and it worked fine, therefore the computer works fine. I hooked the screen to another laptop and the screen worked fine, therefore I thought it was the inverter board which connects the laptop to the screen. I changed it out 2 times with no results. The only other thing I can find that connects the 2 is the LCD cable, so I bought a new one and now the screen can be seen with a flashlight, but does not come completely on. ( A backlight problem) So I hooked the screen to another laptop again and it worked fine, so the backlight is not defective. I have checked all the connections, leads, and grounds and find nothing wrong with any of it. If I put the screen from the other laptop to this computer, I get the same thing, Icons with the flashlight, but no backlight light-up. Also, I have turned off all the sleep mode settings so it should be on all the time. Unless I burned out another inverter, I am stumped as to why this #$@%^&%$#@ thing wont work properly. I would still be happy to hear any further suggestions!! Thx
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Old 08-16-2011, 11:12 AM   #16
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mprovencal welcome to TSF please read the steps GZ has posted above also this eBay.co.uk Guides - LAPTOP MONITOR SCREEN VERY DIM OR DOES NOT ILLUMINATE
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Old 08-30-2011, 06:06 PM   #17
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OK joeten, thanks.
So according to this link the motherboard sends a signal to the inverter telling it to switch the backlight on. If there is a fault on the motherboard then the inverter will not recieve the signal and therefore not switch the backlight on. Great, now can anyone tell me how to fix the fault in the motherboard, or if after all the previous things tested even points in this direction? I know the backlight is good. I know the inverter is good. I know the laptop is functioning properly as demonstrated on the external monitor. I know the LCD cable is good. Thanks so much!
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Old 08-31-2011, 10:32 AM   #18
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By the way, can anyone tell me "Exactly" where the lid close switch is on this model?
HP Compaq Presario F767NR
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Old 09-01-2011, 11:10 AM   #19
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Try this HP F767 Manuals, Support and Troubleshooting - Compaq Presario,Presario Laptops
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Old 09-02-2011, 02:59 PM   #20
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Beautiful, Thx

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