The black screen of death.                  
                   100% HP centric.

I will cover Desktops and Laptops (notebooks/pads) in 2 chapters below.  (I will call them  "DT or LT")  I will cover Windows® "MS" only, not Linux .
Laptops's Only
Desktop's Only.
Display problems only.
BIOS dead.
Solderballs from H3LL 2008
Backlamp failed.
Inverter fix way # 2

For Blue Screens Of Death? (BSOD, backup one page or hit home ICON above, the same is true with windows is only dead or can not log in to Windows.  If you get text on the screen at power on, hit HOME button.
In all cases, we are trying to see if the problem is caused by 3 things, lost power, bad screen, bad MOBO (and all its subdevices including HDD, or shorts inside or dead parts inside)
This page covers only one topic and that is the screen is 100% dead, totally black, no matter what you do, and that includes, the BIOS IS dead too.  (<called "Setup"by HP but it's just good old, BIOS, (38+years old it is)  Example screens here.
Here is an example screen not dead, just to be clear.
The cause is not software, but is hardware, we know that because BIOS is FIRMWARE and always works, so black screens are a hardware failure. (only what? is the question).
BIOS means Basic Input Output System, in a FIRMWARE ROM, ROM is read old memory, that does not FORGET if power is lost (BIOS is in ROM, but it's configuration data is in CMOS NVRAM, with a coin cell at 3volts, to retain said data.)
The LT two big differences electrically, are that huge battery and the internal screen.  (I will not delve in to "All-in once desktops")  The LT also has a   battery charger located on the main motherboard, (MOBO) no, its not inside the A/C line pack at all.
In all cases, we must learn how to test, and discover , is the problem hardware or software caused.?
Try to learn the PCs are simple when they work right, but not so at all when broken,  this is covered well here. A+ Certifications,  read that and learn just how complex computers are, it's no toaster. (sorry)
Just like cars, are simple to drive but not diagnose or fix. (for the same reasons...."complexity") Know to that laptop parts can be very hard to find after 10 long years  pass.
My page below is about testing ,diagnosis , repair and cures. It is not about Guessing at all.  Sure try anothere display on your  dead desktop, but that is test., not a guess.
HOT KEYS: (at power on button and 1second later ,tap tap tap, the hot key, my hot key is "ESC" key. see next photo link)
The screen shows,  THIS !"Press the ESC key for setup !"
The BIOS (setup) is dead if it never talks to you (screen text) ,  the many years of HP progression of the main hot keys from 2002 to now is:  F1, F2, F10 and ESC.  Yes, they changed this 4 times in 15 years. (having fun yet?)
In all cases, remove all USB devices, from PC , as vast things, can short out and cause havoc or "overload". (that includes Esata port to external drives of any kind)
If the BIOS screens and text messages are dead, we listen for the fan, the fan must blow. (or you lost power! or the fan is packed in lent, all do that, packup and overheat, all do , clean it every year and avoid that?)

Desktop: (DT only ,first !)
The First possible failure is a dead screen. (it is a stand alone device sitting there on the table),  It has its own On Screen Display features (OSD)
Using any  External LCD screen monitor, it will always tell you its ok ,eg. a Viewsonic turns on, it shows in huge Red Words, Viewsonic, and I can also push the Menu bottom in the screen, and get the OSD.
  • The LCD has a power button that must work and cause it to turn on, does it? (it will in fact tell you in some why that it is on, does it? If not its a dead monitor. (is it plugged into WALL power and not a dead wall jack (outlet)?
  • The LCD screen must show a sign on message or its dead or its power pack is dead.  (if you went to your Screens makers pages, and read the manual on it , it covers ALL THIS, on pages marked Troubleshooting)
  • The LCD button marked home or SELECT, if  you push that any time ,even with PC off and screen on , the OSD display on the screen must show up. or the screen is failing.
  • If not sure, test the screen now on any OTHER DT or LT with a VGA jack on the rear of said PC.  This simple act, proves, this screen is working or now.  This test cost you $ dollars.  Simple and 100% effective.
  • My screen will also show NO SIGNAL or other errors, if its failing when connected to a running PC.  The monitor can go into SLEEP mode, if yes, turn off SLEEP mode in CP + Power settings (CP=control panel)
  • (some old monitors have this pesky hidden inside, the monitor sleep mode, independent of modern VESA sleep modes. (turn it off) < this is only on RELIC monitors. 15years or older.
Ok the screen works, now. (test 1 done):  we now focus on the PC now.
Next up, we attack the DT PC, with tests.

But first,a factoid:   
Old monitors made before, 2004    fail in 2 common ways,  it is not Plug and Play (PnP) complaint or is so old the MS Microsoft WINDOWS does not support it now.
(Windows , shows it's as a Unknown PnP Monitor) and will fail. (unless special steps and tricks are  done by you. )
The second way to fail is sleep mode, they changed how this works 3 times, and very old monitors will not even have it at all.  This wiki page covers this wild an crazy evolution of monitor PNP and SLEEP modes..
If you expect to own and use, a year 2000 CRT or older monitor, maybe its time to move on and upgrade to LCD screens.? and avoid all the horrors of failing PNP now, that is a wise choice.
If the Display is too old the PC may not be able to PNP scan it or may do that and not be above to identify it due to many reasons, one being its just too old, or is now longer supported by the maker or was dropped from support by MS.
Be it known, MS can fail here, or mixing in old video cards and older displays,  to avoid all horror, try  to keep only 10 year or newer hardware on that desk. 
I will now assume your monitor is not 15 years, old or older,  and the above tests all pass. See monitor issues here, there are many ways to fail, not just 2.

JACKS yes, we have JACKS,  or PORTS called in generic form Video JACKS that can be either analog or digital.   Some PC's have 2, of them. (or more if gaming) Below I cover MOST Desktops .
Desktop has an  external screen. (a computer display monitor)
Desk tops can have 2 video monitor jacks, some even have 2 VGA jacks, and for sure both can be tested.  (if only one DVI jack then we can only test that jack)
In any case, plug in the working monitor  at the VGA jack and turn on the PC, and the screen must not stay black, after the screen power up message (mine shows Viewsonic) 
If BIOS is dead now, the jack is dead. (we already know the Monitor is good above)

The screen can do 3 things, now, show NO SIGNAL or (or other errors)  or shows BIOS  messages from the PC.  or go to SLEEP if  on or 2 wires are cut (means broken) the screen can go to SPEED instantly.
But we know the monitor is ok, and its matching cable. (above tests pass)
Keep in mind even the VGA jack on a PC can fail, and crack and do may things wrong, now.  (no need to list them or wonder, try another VGA card or the other VGA jack now on said PC.)
If you get no signal try the other VGA jack if seen there. (if 2 VGA jacks seen there, to use the mobo VGA jack you may have to pull the COIN Cell for 5minutes to reset BIOS to the main VGA jack , yes tricky)
My DT PC has only one VGA /DVI gaming card in the PCI slot , it has no On board slow, video chips  on my MOBO.  So when mine fails, I try my spare, that I pulled 5 years ago to upgrade my video to super fast card.
Fails Still:
If it still fails to show BIOS messages now , then here are some causes.  (monitor test pass above)  I will try to show all possible way,  what we tech's say  is the Van Neumann is busted.
  • If the fans are dead,then  the PSU is bad. My DT has 3 fans when all 3 go dead  the PSU is dead (or worse, worse means mobo failures)
  • If the fans work and all 5 to 10 power pins show the correct voltage using a voltmeter, then the PSU is not dead and is bad VGA chip (or worse) Listen for beep codes.
  • If the PC or BIOS acts wacky (odd or intermittent), the coin cell can be dead, or below 2.9vdc.  They can fail in 5 years, so...... buy one for $3 or test it with your voltmeter.
  • If all the above shows good PSU then the VGA chip is failing , it or the VGA card in the PCI expansion slot is dead. (try a new card now)
  • The DT can have other cards inserted ,  in PCI slots, remove them as a test, but not the VGA card if its your only VGA or if no spare VGA card to use as a test.
  • The DT has RAM sticks (DMM) remove them and put back 1 at a time, using only bank 00 slot. Most time bad ram causes, BEEP codes, on power up, but can cause BSOD'S,  blue screens,at any time, running windows.
  • The DT can Pack-up in lent easy, and overheat, we clean ours every year,or it fails, the CPU fan loves to pack solid with lent and kills the air flow there dead. (clean it cures this simple problem)
My DT burns 100 watts just the CPU running games its Quad core. (and the GPU more) (super fast clock rates, make lots of heat)
My desktop has 4 fans, in the CPU/GPU/PSU and one in the case rear (large silent fan) most have at least 2, fans, 1 in the PSU and one on the CPU.
You can also remove this card, totally and use the MOBO based VGA port seen there,  run just this port, got video now?,
 (reset the BIOS now, pull the coin cell , see if the BIOS now defaults to MOBO VGA jack usage, the PC has manual that tells you how to do this)(no 2 PCs  brands are same)
Most MOBO have  coin CELL, metal socket holder and the coin just snaps out and  back in.  The Laptops use wired connectors. The CELL looks like a 25cent coin.
If one uses a very very old DT screen connected to very much newer PC, the screen will be dead, or shows "out  of range" , the cure is F8 Safe mode, pick VGA selection on the screen , then while there in safe mode,update the video drivers) Windows 10 is different now, it now does not support many old DT screens 2004 or older? and very old, video cards or its obsolete chips.

The PC must show BIOS screens. this is goal 1 , BIOS screens MUST work, (it's ROM permanent code stored in all PC's  and must work at all time, at power up)  See my screens at the end of this page.
The only tricky part of BIOS, is its hot key keep changing over and over, in time.  THERE IS NO STANDARDS for BIOS or hot keys.
On my PC, its ESC, F9, F11 keys at power on, others use F10. (HP has there own keys and its OWN EVOLUTION of keys used, sad to say but is a fact to live with) At HP they are generational changes.
That means RTM , read the manual for you PC, its stated in all HP PCs made.
If BIOS is dead, it is because of  the above stated reasons.  (PSU dead, Screen dead, VGA card(chip) are dead) There are other reasons that are more complex in nature , say the RAM bank is dead or CPU went dead,
If one of the 2 VGA ports work then the other chip is blown out.
If both VGA ports fail then I'd suspect the PSU is bad.
If all you have is 1 VGA card (port) or one DVI jack, then that card is bad. (if PSU tests pass) On some PC's its only 1 chip on the Main MOBO bad. (I call these e machines, E for economy, in this case add a new Video card to this cheap PC)

If the black screen shows  text at power on "Press ESC to setup BIOS" then the screen is not dead, or black, or if BIOS works when you press the correct key for it, then the Screen is not black, so hit the back button or hit home above.
See blue screen failures or login screen failures one page back hit home.
End Desktops.

The goal
, just like above is getting BIOS working and alive and presenting Screens.)
The HP page for the long 15second power button reset is here (no battery , no line cord, method , 5 steps)
The laptop (notebook et cetera) has different test steps to learn what is truly wrong.
The Laptop screen is not a standalone device,  so can not be tested on another PC. (sure a matching laptop and long hours of hard work splitting 2 LT cases )
The Laptop also shares resources with the actual LT computer, it uses power from the laptop internals. (saves the builder money but makes diagnosis 2 times harder)
The Laptop can have  CCFL back lamp or LED, both can fail but CCFL takes the cake there.(as does its funky Inverter supply module) Just like external monitors can fail the same way.
Here is a list of tests and failure modes.  (power failing tops my list and the 2 ways to get that and more)

  1. The the main huge battery is bad, they can short (even catch fire) and can prevent the PC from booting. Remove it now, and test the PC on line power (120vac (USA) power line and power pack.) Does the PC now run right?
  2. The LT is now on AC line power, if that power in the wall is good and the pack still good the PC runs perfectly , the power pack is 19vdc,  some fail and are 9v, and are bad, volts matters , we test this, or others guess and buy a new $15 pack.
  3. If the PC fails to run it's fan now, with only the AC line power the power pack connected, the pack  is toasted, bad (or wrong pack used or is weak, or you bought a cheaper, lower watts (bad idea that) pack.  Ask HP what size pack to buy, do not GUESS.
  4. If the battery is good, and the A.C line pack is good then the PC is failing, you can now plug in a known working Desktop DT screen on that rear VGA connector of your laptop.       My hot key for MY  PC IS here.Fn+F4
  5. Many common,  LT ,you have the VGA jack above and others, as per, and HDMI jack to do tests for Display data.
  6. If the external screen  works now, then that means the internal screen is bad., or the CCFL is dead. See the next test before buying a new $100 screen, do know that some laptops the inverter is not replaceable its part of the LCD array.
  7. Say now the External screen works, but you do the magic flash slight trick seen below and it shows data, that means the hidden screen DC inverter is bad or the CCFL  bulbs it runs are bad. The bulbs love to go dead, weak or turn ugly YELLOW for White screens.
  8. BEEP CODES:"  The  LT that BEEPS or Flashes secret codes on the keyboard  LEDs on top of the laptop. Tells you what is failing, on mine it flashes the Caps Lock LED, keys.  Kinda like MORSE code, but not.
  9. Last on not the least is the BIOS, get the BIOS screens working first.  using the above, tests, and methods.  
Other causes for BIOS to be dead.

The AC power pack creates DC power and goes to the LT D.C power jack its 19 volts Direct current that any meter can measure if you want.
DC power jack and you find a wire broken here, the jacks that break are all soldered directly to the LT MOBO

If the DC power inside the PC, (LT) is wrong,dead weak , that means the mother board fails, the screen fails and the BIOS fails.  (3 things die,  the top 3 main things are now dead , even the fan can go dead.) 
This takes a skilled technician to find this out. (using a magic tool called a VOLTMETER)
The VGA jack on many brand new LT ,  is missing now (its too big to put one there...) on all new LT (notebooks that are super thin , now) with  exceptions below...
The newest HP notebooks you must buy and VGA adapter cable to do this magic.( costs extra)
The new HP uses a NON INDUSTRY standard, video jack there.  (a royal pain this is)
Here are other failures and common problems with all LT.
  1. Is the 3vdc COIN cell battery dead,?     I only allow 2.9v minimum here, never below,  The battery maker states 2vdc  is end of life, never run your battery to 2vdc.  replace before that. Buy a top brand battery, not a counterfeit. (BIOS flash code 2 is common)  The BIOS will forget settings when this battery fails. The PC may also not keep time and date correctly, this is almost always the COIN CELL is DEAD.
  2. The screens goes dead? if I wiggle the power line cable ? or comes back? from dead./? the Cable is bad, (there are 4 ends to fail, so... test carefully or replace the whole power pack.
  3. Does the screen wake up if I twist the LCD outer bezels (wrongly but very  gently). Does the LCD have funny lines there or go away or come back twisted gently , yes, then that is a bad screen.
  4. On all PCs the CPU or GPU can overheat (shuts down) due to bad thermal compounds at the heat sink CPU juncture or dead fan, or lent packed up there.
  5.  This overheat shut down, can be as fast as 3 seconds from power one, this shutdown. (it's by Design this feature, it's self preservation  this action.)
  6. The vents must not be clogged up, the vents and deep in side is a tiny heat radiator that must not be full of lent or the CPU will overheat and shut down,
  7. Keep in mind that overheating can take an hour.  (if the vents are partially clogged, or you run fast games , in this condition)
  8. Running any laptop on a blanket will cause it to over heat,  you are suffocating the poor thing.
  9. All PCs , have modules and sub-modules, if any one shorts out, the power bus, then the PC fails hard, in many a way.  We remove them 1 by 1 to find out if this is true.
To clean the fan use CAN-O-AIR or shop AIR (called an air compressor) and vacuum at the same time.
A vacuum alone will never get this tight points cleaned, ever.(best do this outside, or makes a huge mess indoors, and lots of sneezing...)
We do this every single year, for 30 years or more now. (or it will FAIL and overheat)
The LT has  small radiator on one of the air flow exit ports, this is the main hot port that expels all CPU/GPU heat , this radiator can pack solid in lent as can bottom vents.

Do learn that heat is the #1 cause of electronic failures, in fact, the makers of chips use heat to check life spans  of chips (all Military chips are done to  greater extent here, using heat and clock cycling.)
That means keep the dust  out of your PC, and all fans working.
All PCs have fans, because they are all capable of fast speeds and when run FAST they BURN lots of heat. (unlike weak slow CELL phones)  Running CAD/CAM/or modeling programs or expensive puter games, all burn lots of heat,
Your job (its) is to expel all that heat or it will FAIL, and FAIL HARD.

Respect the heat, learn to avoid it getting out of control.

Now the long story.,.. examples can help...

Next are EXAMPLES , real:
The goal here is only BIOS working on this page....
so what can BIOS do.  ? (a short list)
  • It can show many screens. (even tab screens)
  • It can show the INFO page seen below.
  • It can allow you to set any possible Boot-able devices. (and BOOT order or enable them or disable them) It's programmable , all this is, by you the owner.
  • On my Desktop I can even see the fan speeds, (RPM) and all DC  power line voltages, 5v, 12v and more....
  • It has  RAM test and  Hard disk test, both are very rudimentary but If they fail, take that to the bank, as true.
  • The HP manuals cover all this, but our goal here is just getting the 1st BIOS screen ALIVE.
  (BIOS needs no HDD /SDD to work, ever) BIOS is the minimum intelligence in the system (near); it's a ROM full of machine code, ready to run at any time you want. (at 1second  of power on time)
I push the  power button and then tap ESC on mine, (tap,tap, tap) until the screen says,  Entering SETUP. (in white text over a black screen)  this message proves its not a black screen PC,  see?
I then get the BIOS PAGES on SCREEN now.

When you boot the PC you see BIOS hints on the screen white words, on black, that is BIOS talking to you,  on lower left corner for 1second "Press ESC key to enter startup menu" this is BIOS. (CPU machine code ROM running, brains !)
eg: my HP8540w LT , If I press F1 my screen goes white, with BIOS INFO page, if it hit F10 at the above ESC prompted I go directly into BIOS setups screens, see your PC is NOT DEAD , is it.?
These hot keys, are different, on each makers PC, and is covered in your service manual,  so check it out. (All PCs, LT or Desktops,etc)
Beyond simple checks we can go deeper...  

Next I go to and read the BIOS page documents on my exact PC. To learn what KEYS MINE USE,  (varies by generation of PC and makers.)

Here is my list of keys,, like ESC, F1 F9,F10 F11 (F11 is restore OS, on older machines its F10), F9 is boot on the fly options.

But only when prompted, this can be a 1-3 second window of time (you can make it longer if you want , in BIOS setups.,  Set to 1 second makes entering BIOS super hard, do not use 1second settings there.
If you see these words? the hot keys, will work now) To see relic hot keys see this really wild old page here.

HP covers all these basic facts here on hot keys.( Modern kids call this "Spamming"  the BIOS key.) (like a  wood pecker bird does.....) MINE IS The ESC key, (ESCAPE) top left corner of the Keyboard.

Can you reach a BIOS screen?  The BIOS screen can be actually there but is invisible do to a DEAD SCREEN BACK LAMP.
 (You must, and if not, we must  cure this hard failure first and now)

THE FLASH LIGHT (Torch) trick: (dead back lamp tests)

One can also connect any VGA (15pin) external display to my rear LT 15pin matching jack and now see BIOS or even boot to Windows.(or boot from CD live Linux to test the LT screen)
There is a Fn hot key to enable the rear VGA jack, mines set now to auto mode. (magic) Fn+F4 on mine. (mines set to Automatic)
If the rear jack is dead VGA, the Video card is dead, or the power pack is dead or weak. (power packs that overheat are usually the wrong wattage pack used (or just plain old bad) and can cause crazy problems)
Newer Notepads have  a HDMI port , that you can connect to your TV and see, OMG, my laptop does work.... (mine does!) I can use 3 screens on this LT, built in LCD, external VGA and HDMI TV.
Most cheap laptops have no VGA card like mine has, so if it blows out, the MOBO (motherboard) is now dead and useless. (means time for a new or used one)
What else?, well there are lots of checks, it's just a computer, and BIOS screens always work, if there is good DC  power. (sure, good CPU/GPU/RAM heck the MOBO good in total, including fan and heat sinks.)

ALL most all PC's made can produce,  FLASH codes,  or BEEP codes, newer PCs use flash codes and HP tops this list. ....
See my Blink Beep page.


Ok,  more tests , deeper!
Laptop Case top off.  DC POWER checks: 
I get to my power connector inside, LT and and with my magic voltmeter it's 19vdc on those 2 pins there,  turned on, telling me power is okay.    We can use a $20 DMM meter from Walmart ,to do this test.
If the 19v is low, say I measured 15vdc ,I'd try a 2nd pack if its low, then the laptop has shorts. ( I have a 4 ohm 100watt test resistor I use to test my power packs, by them selves. )
I can remove many things off that MOBO. To see if some option there is shorting out power. (video card,wifi,bluetooth card, DVD drive, RAM, card reader card, and more , keep and open mind, anything can short out)
To see if flash codes  change or  go away as I pull or add things, do not hot switch parts, have the huge LT battery out all the time, and pull the line cord before each test. 
(I wait for 2 -5 minute pass before removing or adding parts at this deep level, letting many internal Capacitors discharge fully and  naturally)
See , me doing magic testing here?  Most folks don't know this. I can run the MOBO naked like this, NO CASE ! AT ALL.
I have almost all things pulled here, but not CPU/GPU, even the fan can be pulled for 1min test to see if BIOS wakes up, keep a wide open mind on what can short (answer is ALL THINGS CAN)
See my A.C.  power line left top? MOBO, See LCD? that just plugs in? See a DELL USB keyboard there, (original key board is not plugged in)
 See fan spin fast? at power on? it must,  See BIOS work?  I could even boot to windows if I added the HDD now.  (no loose Heat sinks allowed)
Do not forget the BIOS has a Hard disk and Memory bank test. Run that now.
I do most my tests on an anti static ground work pad, and cardboard of that. The only rule is to never run the CPU  with out a heat sink. (and a working fan)  That cooper pipe below must be fitted correctly at all time.
My video shows me running it CPU free. To prove lamps flash even with it missing.
  2011 made PC HP8540w
This is my most loved LT,  I always buy them dead and repair  them or buy them in bundles of dead, fully complete, Laptops , but dead.
Below is my 8540,  one can see there are 5 modules you can pull to see if BIOS wakes up,  GPU card, WIFI, VGA GPU, SATA and express reader card,.
You can pull any module you want to see if problem end, but you will get flash codes for most pulls.
We do pulls to find shorts. (1 small example say I pull Mister WIFI  module and the GPU wakes up. that means the WIFI was shorting the power or data bus.

Keep in mind GOAL #1 get BIOS screens working and then GOAL 2, get something anything to boot.
On mine I can pull, modem, wifi , VGA outrigger card, the whole Express card assembly comes out. This card Express has the power status LEDs so if pulled you lose this information.
This PC loves to flash the caps lock keys, or Numlock key LED's in fancy codes. but not if the CPU is missing.
I can even pull,  GPU video card seen here, Keeping 1 RAM stick (DMM3) and one CPU,  this mobo even has a flash code for CPU missing, (yes)
We pull things why? Answer to find things that are bad shorting out critical power buses.  Shorts happen. we find them this way. (learn that ALL THINGS can short out)
What do shorts cause , answer, it overloads the power bus system and kills key functions in the computer.  (or worse)
See the DVD drive pulled, HDD pulled.
No two Laptops are the same, parts locations, (there is no standards here) Only you can read the HP service manual and see what is there, and not.
Taking any LT apart like this takes, skills.  It is not a casual practices like it is on any simple standard DESKTOP. Some LT are very difficult to take down and must be done in the correct order, and not breaking fragile parts.
Most Laptops, have no GPU card like above, on mine the GPU was upgraded by me.(easy) Seen above as GPU. card.  (I buy laptops that have a card here, or don't buy that model)
Keep in mind that some USB3 ports will be dead, until the correct HP drivers for it are installed. (that means use the left  USB2 ports to boot from any LIVE CD BOOT sticks (Linux or Windows PE)
That also means testing USB keyboard at boot time, use the USB2 ports ONLY,  not my 2 USB3 ports seen on the top right. My BIOS does not use them.
One can test out most of the PC with any live boot disk, even with HDD removed.  (costs you , the price of one CD or USB stick) (to burn a CD find a working PC with a CD or DVD burner and burn away)
I have 2 boot USB sticks or UDISK as HP calls them one is Live LINUX , and one is LIVE WINDOWS PE (I have w7/8/w8 at the ready) I can boot this way from STICK or CD or DVD.
The burn software is free, Imgburn, (Google it)  I avoid CD like media now, it's slow and time wasting, I only use boot able USB memory sticks, totally, today.
I use RUFUS, to program the USB sticks from and ISO file, (Linux or live windows PE) Best is always have this stick ready for testing. (in advance)

If the BIOS works now, and the HDD/SDD will not boot, and  the boot from Live Linux, and tests ok ,LIVE boot tests work,  then that  OS on you HDD is corrupted/infected ,  reload the OS, is the cure.
The HP hot key for RELOAD the OS is , F11 on mine, power on , tap, F11 (older PCs use F10) MY OS IS windows 10, what is yours, know what you have first.
Go to and get the Media kits to reload the HP software, on any HDD that was dead or replaced.  Hit the back button  (or here)  for more facts on Blue screen failures. Blue is WINDOWS failures.
Peeling the Onion deeper, is always possible?  if A chip  bad,  replace it, but wait, it has SMD chips , Surface Mounted Devices ,some are flea size. Lacking very expensive tools you will not make that work, and even with them fail.
No lie, all those modules seen above are sold on ebay cheap.   Do so and win.

If you see this, it's not a dead screen at all.
This is the GOAL getting here,  this is my MAIN BIOS screen on my HP 8540w .  Best unless a super geek that keeps records, stay the H3LL out of the Security page. One can even turn on BIOS finger print mode. YEAR 2010 PC.

Here is the first BIOS page, that lets you go to all BIOS pages, inside the FIRMWARE ROM.
I pressed F10 to get the above screen.

I'm not going back to 1979 here, sorry. or to HPs 1984 first laptop, ever.
On old relic PCs running old (Blast from the PAST YEAR 2000 , 17 YEARS AGO....) BIOS V4 from say , Phoenix?  
You see this,after hitting F2 like woody wood pecker.(at the instant of power on button pushing , you) I guess this is 1994 below. (or older) or new HP computers use ESC key to get to BIOS. Then  F1 to get to INFO page,  I do this first. find INFO page, as  a test.
This is out of the Phoenix book, what could be more clear, how to get here, and what is there?  See the HDD here? 6.449GB?

Here is one more relic BIOS page,  the old ones ,where like this.  Below if all HDD are missing, then the HDD is dead (or unplugged).  These are PATA drives here. Primary and Secondary.

Rules of the road, and electronics, savvy:
Rule #1 is "first do no harm", (why make it worse?)
Rule #2 , power is first , not just the power cord to the wall is hot, but all DC supplies, and regulators must be good, or all hope is lost..... hopeless, to proceed it is... fix that now.
Rule #2, if boards, cards, batteries, modules, or anything is shorted, you will not get far, until that is corrected. (unplug as many things as you can, even USB things. and if brave , things deep inside, or get a technicain to test it)
Rule #3, if the fans are dead, that is  big clue.
Rule #4, if the old HDD makes no sounds at all (it has motor inside) then it is DEAD, or unplugged. (or worse, sorry worse can happen)...
Rule #5, if the screen is 100% dead, and never once even shows some white text, the PC is now DEAD, due to no power, or a dead screen.  more tests are needed.
Rule #5 , if BIOS works and shows the time clock date function is nuts, well it is, and the coin cell is bad.  all do after say 5 years. (10 max is the makers rules)
If the PC is old, and time and date act odd or BIOS forgets things, the COIN CELL IS DEAD (3v Cell) ( be aware that while in the BIOS screens you sure can see time and date ,directly from the RTC chip)
The first rule of electronics WORK, is never hot switch parts, means plug or unplug THINGS,with power still turned on, and not discharged first.  (learning this the hard way will cost you big cash)
Exception 1: USB ports are hot switchable as is the EsATA PORT.(BY DESIGN)
Almost all electronics have huge capacitors inside, that hold a powerful damaging potential charge  and ignoring this one fact, many folks (noobs) blow up good parts in the PC.
Remember Ben Franklin's KITE, trick with lightning, did you know others copied him and died?  (by the lightning dirct or touching that Lyden Jar (that cap) the lesson here, is learn not  to play with caps, unless you learn how the work first, (they hold a huge charge)
On PC the voltage is safe but the current can and will blow up parts if you fail to discharge them before servicing any PC , deep in side... (and for sure unplugged from the wall and never ever short out the battery)

Here is how to think when getting the wild notion to flash your BIOS FIRMWARE for squats and giggles.   (the do no harm , rears its ugly head) Best is to leave BIOS alone unless HP tells you it will cure your specific problem. (it is a huge risk)
If you blow the  BIOS UP, what then?, can I unsolder the chip, to replace it?  No.  (I did replaced them many times, I put in a socket there and could run different BIOS that I created "custom features")
If you , have  HP Probook or Elitebood that needs the flash upgrade , learn that it can not be regressed, you can not downgrade it , after a failed FLASH BIOS EEPROM BURN. In fact on the HP BIOS page click ROM.binary DETAILS, see those same words, yes.
You will have to get HP help now,  now that you BRICKED  the BIOS.  (they have a reset flash, but is not online this ROMcode reset file, you must ask them to get it... do so now...)
Some more modern BIOS, the flash programmer and boot code parts are protected and you can flash the BIOS over and over, for say when you use the wrong BIOS Binary files for the wrong MOBO. (ALWAYS ASK HP for help finding a perfect match to your PC using the PC service tag)
The book on this is clear, the main laptop battery needs to be GOOD and fully charged , on a desktop a UPS supply is best here, so if you lose A.C LINE power, the BIOS is now scrambled, but if you have UPS or BATTERY there ,you are good to go.
On a Laptop if you have 2 sources of power there, the line pack and  good battery. (and the flash can be robust, that is if you have the correct BIOS binary Files... matched,  as it seems most get this wrong, guessing)
Never flash any BIOS if the LT battery is bad, or weak or discharged, or you can be very sorry soon.
Flashing means to program (or as they once said BURN) the Flash EEprom CHIP. (called BIOS) it's FIRMWARE, software in SILICON. It's a ROM. (all PCs made were ROM, EPROM ,EEPROM or FLASH, in order of progression) Flash is faster, EEPROM.
Best is leave BIOS alone unless you know for fact the BIOS upgrade is for your exact problem and a perfect match to your PCs serial number..  (and HP tells you to mess with it)
I see one more PITA,  HP has a UEFI BIOS update , due to security holes in it (bugs).  So many read that and flash the BIOS and brick their PC's , lots do,,,,,  Why do that,?   (the no Regression path by HP I think is UEFI laws... in effect...) IMO.
Know that UEFI wants to block all removable media.  (to prevent virus infections, by DESIGN)
If you don't use CD./DVD/BRD/floopy  media with programs or exe files on them, then why worry this,  MP3 files on CD is not an  infection ever.   Why not just first turn off AUTORUN and win,  the most dangerous thing ever invented is that feature.
Reading EMAIL attachments or links is the #1 bad way to get infected,.
Or going to web sites, full of viruses..  I run software that blocks all such sites. (Google how)
I run MBR boot disks and not UEFI BIOS, so its not ever and issue for me.  I wonder how many PCs get bricked in a month with people flashing there BIOS for fun.
Best of all is run windows 10, for max protection. (buy a 10year or newer PC and upgrade it to Windows 10, if you value you , data, bank accounts, or your identity, do so now)
Never let anything store your bank passwords or login ID, ever.  (keep them in your head, only)

DISPLAY's 101:  (all) A short History and lots of tests and cures.

In the dark ages of PCs, (in the 20th Century, yah) we had CRT, Cathode Ray Tubes, just Like Karl Ferdinand Braun did in 1897 just now in color and huge complexity. (yes, a huge VACUUM tube)
 They are now gone, so forget CRTs existed. (they lasted for 100 years and are dead technology now) RIP!
Next, came LCDs the first HP LCD displays had a power saver clock inside, to put the screen to sleep after a period of time,  this DISPLAY is old, 2001?  The OSD menu, has a Power Saver there (INSIDE IT),  turn that off now, we use VESA today.
PnP or Plug and play (pray?):
Then the new VESA standards added sleep modes. (and is related to PnP, plug and play, the OS must know what display is there or it can not set the correct resolution mode, on old CRTs guessing this can burn up the color screen phosphors.
When you boot any PC the OS sends out PnP commands for what screen is there, using PnP (PCI) messages, if no answers come back PnP fails, if it comes back and the message is so old that Windows can not support it, then it fails. (one way to get past here is use Window SAFE MODE)
 The GPU card or chip (and friends) could force sleep, simply by cutting dead either of the 2 SYNC lines to the Display,  (they changed the rules 4 times, to make all this fun) (not)  The screen now shows, "NO SYNC" errors... or shows Sleep mode, (or the like kinds)

The LCD is not a light emitter like CRTs were, it is only a contrast device.  (that means it can not glow ever, like say a true OLED panel), most screens Tagged as LED are really LED black lighted LCD, so the user can see what's on the LCD matrix before you.
The BULB's seen on most  old PCs (and monitors) are Florescent lamps that LOVE TO FAIL, from  5 to 10 years old , the maker claims 20,000 hours or 2.2years run full time)  This bulb tube is called CCFL. (they love to yellow too .see CCFL comments below..)
(LED back lamps can last forever, or far beyond other parts there,I have LED clocks that are 42 years old and still run like day 1)
The display or Laptop has 2  dim buttons (up/down), if set low, the screen can be too dim, (obvious) but not so obvious is the button on a laptop needs a special driver to make this button work at all. (and the HP control panel DRIVER to match it.)
The CCFL goes dim  and somethings we push the up button to full brightness and bingo in a dark room, we see a working display  , but useless, unless you are in a dark room. (a classic CCFL device failure)
 (if you upgrade the OS this can cause this GPU driver to fail, easy, so use only correct matching HP disks or matching HP drivers seein on HP.COM to upgrade or reload the HP full OS, Operating System)
WINDOWS also Auto dims displays too, on all laptops made,  new out of the box the Control panel + Power settings, if you look all  go  to dim mode, when on battery, so you can turned off this FEATURE. This FEATURE is to extend battery life, while on battery.
Windows also, DIMS the display on battery mode operation or if say on battery mode, the power levels are too low. (weak battery) this is to make the battery last longer, its a FEATURE, if you don't like that , turn it off.
(Windows, features that can effect this are, Sleep, Hibernate,screen saver and low battery modes) All of these can cause you a problem. (The windows control panel, power settings is the place to look first)
Some newer PCs have a autodim that dims the Backlamp, with a dark room and the reverse is in bright sunlight, using a magic photo cell, device, to measure said background light or uses the WEB cam  to do that.

Like most things in the real world , most things can be good, bad or dim.  (weak, intermittent or acting very odd)  GOOD bad or shades of gray... (the universe is analog , not digital)
The CCLF inverters also LOVE to FAIL.  Many of them run real hot, and do fail often.
The inverter converts 19vdc to high voltage that the CCFL needs in order  to glow CCFL. 

Diagnosis is very simple, in most cases, the first test, if the screen is black all the time power on, is use a Flash light

If you see the below, see BIOS, or Windows login, the screen really is not dead, is it?  only back lamp issues.
Also if using a screen saver, (don't) this too can cause problems.
Clues common:, monitors power button goes yellow or orange not green, the Screen pops up a message (OSD brain inside did that) and says, lost sync, NO SIG, or Sleep mode, or power saver mode.  All mean the PC did that on purpose, in most cases.
If the Displays OSD is dead, the monitor is dead, or lost power. The Menu key on all desktop monitors must work, or power is lost or the monitor is now DEAD.
Sure a bad monitor cable can do this.  sure. (but will not kill the OSD)  If 1 SYNC line breaks the monitor goes to sleep mode. VESA rules, tell you all these facts.
A laptop has no OSD brain or menu's, so just goes black for sleep mode.  I pound the space bar to take a PC out of sleep or deep hybernation,.. can take 3 minutes to wake it up.
A laptop can use the External VGA port,  15pin D-shell and to use said jack on HP, hit the Fn+F4 key pair, and pick external, both or auto mode. This is test #2 after the flash light test.

Top fails: (first are old screens, with CCLF) (for sure if OSD screens are dead)  OSD is only found on desktop monitors., if BIOS is dead, this can be it)
CCFL is old school Cold Cathode Florescent lamps.  (with a 2.5year shortest life span possible, most go 2 times that easy) No LED fails this fast, none.
That love to go bad or dim and turn yellow,  newer LED back lights, new Displays just keep going, like a Timex watch. 
For most OLD LCD displays, that fail for this , the cost for the parts alone (labor omg more) is more than this old LT/or monitor is worth...
(but you can connect any external VGA screen and use that, and abandon the internal LCD screen.
 Walmart has  nice $50 display for sale, why not upgrade to LED display now.?
Top failure modes:
  1. The DIM button is on lowest setting and screen is too dim to see...Push the up brightness button now. (if the button acts wrong see then next line below)
  2. The software that runs said button, (a laptop) the driver is missing bad , corrupted, or you upgraded the OS and now is MISSING !
  3. The display LCD-CCFL is dead, or its inverter and you can prove that in 1minute flat with the flashlight check below.
  4. On battery power the Laptop(LT) does dim the display, if  the AC line cord missing, not plugged in properly to WALL power outlet.
  5. The Battery can be bad, even shorted and now overloads the Laptop, remove it and test the display now,  see it now works?
  6. The LT Line power pack is dead, weak or intermittent even the cords looking bad are in fact bad.  +19 Volts DC. is good. At the HP main jack. (this causes the battery to go dead and with it a dead PC)
  7. This page here, is not for dead windows or BIOS Dead, if you can get the below the PC is not dead, nor is BIOS. If BIOS is dead, with a flash light below, hitting the hot keys for BIOS, then that is  a DEAD PC.
  8. The screen can fail for 2 reasons besides the CCFL, a dead power supply or Bad GPU chip or Graphic card.  Some PC's have 2 VGA ports, try both.
  9. A dead PC will be silent, the HDD is silent or the fan is dead , no sound from fan, or the PC is overheated. The PC can even shut off, for these reasons and more. If the PC sounds ok,  then the Flash light check is next. Seen below.
  10. A dead PC is very complex, but in the macro view, it's a bad MOBO , or GPU, or bad LCD SCREEN or overheated CPU/GPU or the power supply to the system is bad or any of its regulators. A shorted module of any kind inside will kill it dead ,until removed.
  11. A PC that sounds ok, but the below Flash light trick , shows BIOS OK, then it's NOT a dead PC,  (my definition) , in this case its CCFL failure.
  12. The external monitor that fails it's menu test, push its menu button, and not get the OSD menu, is a bad monitor. (OSD is the monitors brain created, ON Screen Displays)
  13. A Dead DT PC is usually a bad PSU, (or CPU overheats Fast)
  14. A laptop can fail and be in great condition,  most things work, but getting the below screen is JOB 1, do that first.    The goal is get the BIOS screen working FIRST.  The HDD can be missing and BIOS works perfectly.
  15. One top test is fan tests, if its dead, you lost power, or its packed in lint. The fans must work, for sure at the power button on moment.
When the world runs out of old silly CCFL screens,  this test will end .  Most screens that look like  this below, are then sent to the trash. (why spend big bucks a used and bad LCD display?
I take my flash light, and point it to my black dead screen.  I see data here, this is BIOS but can be Any windows screen of any kind ,or even a login screen. See, it's not dead is it; only the Back lamp is DEAD, (and must be replaced)
      what could be more easy?

When I see the above, (I have repaired many )  but I get this monitor from walmart and use it. Even on a laptop with bad $100 screen , we add this, and abandon the internal screen. That is a plug in the rear VGA jack fix.
All HP LT have service book telling you the steps to remove this screen and put back the new one. (some LT have no seperated inverter cards but deep planted the display)

Walmart has a list of REBURBS here , some cheap as $26 bucks.

Why fix any monitor with the above so dirt cheep, gee its less than a potted plant. Oh My Golly, OMG !
But if portable is necessary, then you must fix it, and below that is what I am doing.... One more inverter fix, in a very different way.
Here I am upgrading the CCLF screen to LED Back lamp screen, see the new Inverter dead center. (the screen was cracked so I upgraded it) The Genius level inverter here fits vast numbers of laptops. The extra connentors does that.

Solder ball H3LL: CIRCA 2008. 
This is a surface mount device, SMD, and uses solder pad/balls, If you look at it, you learn in 1second flat its not easy to do.
 (I will demonstrate this using a better LT PC, one that has  totally modular , VIDEO CARD)
(this can cause a range of wild and crazy symptoms, and for sure  intermittently and screen acts crazy as the  LT base is flexed.)
One more clue is the rear VGA  jack fails (using and external monitor), too when the PC is flexed,  (GPU failures)
 The 2008 era, LT have the GPU solder ball failures from H3LL problems cause by the USA Federal mandate of lead free solder, laws.{think Monkey wrench effect}  (yup, it was born dead, complex thermodynamic reasons, low melting point solder) 
The are 3 reasons for this failure, 1: not putting a steel stifferer frame on the MOBO, 2: a bad  brand of new Lead free solder, (too low melting point) and at the same time, if lap top vents are blocked you can overheat the GPU easy,
Also some PC overheated fast and easy. (some LT makers just hid the problem by running fans full time or 2 times faster all the time) (dead displays)
If sitting on a beach at 120F in the shade, and the LT goes dead, are you surprised? Most will overheat like this and worse if the sun lands on the LT.
One LT, if you press hard on the J key  , the  GPU bad solder balls, connect and  the screen wakes up, or goes dead. (yup).
Or,  remove the key board and press on top of the GPU chip now,  does the screen wake up now? BINGO? bad solder joints you HAVE! (kiss off one MOBO) but not mine below, it's an Elitebook.

My GPU unplugs. (GPU means Graphic Processor Unit, or chip)  Yes the chip runs hot, and has heatsinks, as do those fast RAM chips seen here.
The large chip below is it, and will overheat if the heat sink is missing or fell off.  (loose or the thermal compound is cracked)
The other chips are dedicated RAM for the GPU. The RAM chips on mine have heat sink pads. 1mm thick (I reverse engineered them, 2 ways, the pad them self and the gap measured.)As seen here.
Do not let hacks fix your PC or they many make it worse not using proven heatsink compounds or pads, the correct thinkness. 
Warning 2,  I see laptops failing for GPU too hot, I then check the heat sink and find that the compound is now hard as dried clue and brittle,  and is now CRACKED from natural LAPTOP flexing.  What ever they used there for compound is NO GOOD. I use this.

My Graphics screen driver CARD: below:  (HP Elitebook 8540w)  My LT has 3 card options. (speed)
I love only Laptops that have a card that unplugs, (you do get what you pay for here!!). (not only that, but I CAN UPGRADE IT for gaming, or for CAD/CAM or for Video editing extreme. Yes, PCs are versatile.)
Some cards sell for $20 used.  (what a deal and not one has Solderball problems !)
The solder balls (SMD) are under this big green chip below, called the GPU, graphics processor.  (the conditions of assembly here are complex, Reflow methods in an OVEN)
It runs real hot, the better and faster the chip the more heat it expels (like gaming does),  The balls can not be home repaired,  doing a ball remelt in moms oven is 100% failure event, I can replace my card but most cheap laptop owners the MOBO is bad now.  $150 used part. or more.
This example below never ever fails for solderballs , but the photos of my GPU are very clear, and you can see no human can go under there, and fix bad balls. (only a reflow oven might but at home is  hard fail to try)
HP 8540w
The test to see if this chip is bad is press on the Keyboard "J" key the chip is below that key, on your LT the pressure point would be different, read the service book to learn that location.
or learn to twist gently the whole base of the LT.  (a bad screen can be tested the same way, twist the screen bezel, gently) see lines,? yes, then , bad a screen.
I can also remove my keyboard and then press the GPU chip to my hearts content, to see if the screen acts up.  (2008 is the year of horror for said chips)
A savvy Tech nows there are 3 classes of failures,  bad electronics, bad connections or thermal dynamic problems.  (things can overheat, and If you do not know how to solve those problems you fail as a tech.) (air flow, heatsinks, heat pads, and lent packing air paths)

This is not a black screen of death, at all ,see the HP logo? , these words from BIOS?.
The above shows me the you have power, CPU works as does display, and memory and the BIOS is alive, and the HP logo is from the BIOS code.  I'd say if you can't get a boot from the HDD NOW, then HDD bad or the OS is corrputed,  Go in to BIOS now and click HDD tests.
If you F9 booted to say a Linux Live disk or usb memory stick boot of Linux now, you learn that the whole PC is ok, but only HDD is dead or its OS IS CORRUPTED.  My F9 key at power on allows me to boot to vast things. 
When I say HDD, I always mean both, HDD or SSD , which ever is your case.
If you can get this screen and  a boot CD works (Linux live or Windows LIVE PE works ) or same way using the USB memory stick boot, then the PC is basically ok.  (that means the real problem is, HDD failure or OS corruption)
If the HDD tests pass, (learn how to test HDD and save data) then the OS is bad. end story, hit F11 and reload OS.  (if F11 key  is dead, magic restore , then you need the HP media kit to fix that.)
On older PCs F11 is F10 restore HOT KEY(if the HDD was ever changed out F11/10 will be dead ) leaving only one solution. the media kit, from HP.
On even older PC's, there is no such restore HOT key, (some are named Compaq) and you need the media kit to recover Windows. (click kit link above)

Version 4.  5-9-2017  ( a work in progress)  I'm retired but not dead.  By : DeadPool. (retired)