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 but not all 14 versions .  (XP forward in time, 2001 to now)
The HP page for this failure class , is covered here, (20 questions)<< one question missing here, is "did you install an  OS not from HP media recently" if you did, please see the slammed page here.(this usually caused blue, recovery pages to pop)
Black screens are more serious, and the most serious of all the total dead screens , cover below, or just the screen is dead (only)  ( not to mention beep or blink codes (from caps lock led)  covered here.)
Mini-Menu: "black screens"  if you see text , then it's not black screen is it? What you see there, is very key to what is wrong. In all cases.

Laptops's Only
Desktop's Only
All Display problems
BIOS dead
Solderballs from H3LL circa 2008
LT power
BIOS hot keys.
The logic list of tests.

Black screens have many causes... (screen bad (backlamp), HDD dead, OS corrupted, or molested by geeks slamming the BIOS ROM (eeprom))

IN GENERAL:
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 black screens: (DT only ,first !)                          JUMP TO LAPTOP NOW?:            Jump here if BIOS screens all work.
Starting here , BIOS newer shows text every nor the HP logo ever, if that is true these next steps cover this case.
The First possible failure is a dead screen. (called a PC monitor of vast types.), 
The dead monitor page is here, ( dead and tests (the good the bad or  ugly ) click desktop there , the "all in one PC"   is an almost Laptop , in truth...( they moved the PC into the monitor case)

Ok the DT monitor  screen works ok, as is it's cable.  (you can test the monitor easy on another PC, or test your PC on another monitor easy, be savvy to do that now)
Next up, we attack the DT PC, with tests.
DT PC's have 3 different possible (more back to 1981) Video jacks and matching cables. (VGA, DVI, HDMI)  Jacks. Video Jacks,
If your PC has 2 jacks there, it is  best  to test them all first, to  see if one works ok.
Ok the monitor is ok.
If not?, replace it now.
Next is Power,  the PC power button seems to work.
The fans all must blow, and are not packed up in this lint dirt.( PC's can overheat fast and shut down fast,in fact can do so in seconds)
The DVD tray ejects (omg it's only a CD there, same dead? try) if not working this, the  power is lost.
If BIOS is dead now, the VGA jack is dead. (we already know the Monitor is good above)
BIOS will be dead if power is dead or weak, in all cases. BIOS works even with the DVD drive and HDD/SSD drive cables pulled. BIOS IS always the FIRST GOAL.
BIOS can go nuts, if the coin cell died at 5-7 years old, the makers of them spec that at the life span, believe it,  when weak the BIOS setting are lost and the RTC time clock goes NUTS.

The PC side still Fails  !: The DT , desktop, dead.
If it still fails to show BIOS messages now , then here are some tests and causes below.
Monitor tested good.
BIOS dead. ( If BIOS is not  dead jump here)
 I will try to show all possible way, for BIOS to go dead   what we tech's say  is the Van Neumann is busted.
The BIOS message that must be seen is, text, is "Push ESC key to enter SETUP"  this message must be displayed and that KEY  to work right. IF not, this is a DEAD PC, (assumes display is ok) It can be a DEAD PCI VGA card, or is overheated and packed in lint.
  • Power Button seems to work ?  and the fans run, mine has 3 fans inside the MUST work right,  PSU fan, CPU and GPU fan, if not the PSU is bad or sees mobo overload or the power botton wires fell off  or kids flipped the rear PSU (on it) power button to off (0/1)
  • If you hear fans work and even see them , push the CD/DVD drive botton, for eject , if this works 5vdc and 12vdc are mostly ok of the 12 power rails,  but there are other voltages from the PSU that must be good too.
  • If the fans are dead, then  the PSU is bad. My DT has 3 fans, when all 3 go dead  the PSU is dead
  • The PSU can be bench tested with 1 jumper wire.  Know that all PSUs shut down if its overloaded, by any means,....(my PSU is fancy , and shuts off for over volts or current or under volts. on up to 5+ rails and for overheat and for fan inside dead, yah fancy)
  • If the fans work ok and all 5 to 10 power pins show the correct voltage using a voltmeter or DDM meter
  • The VGA card can be bad, or shorted, if it shorts the PSU shut down. if the PSU stays up the VGA card can still be bad (or the onboard VGA chip)
  • The VGA/DVI/HDMI  chip may be failing ,  This GPU chip can be in 1 or 2 places,  PCI slot, or on the main mobo, or both.  If you have 2, chip pull the VGA card and test the on board port now. BINGO?
  • If the PC keeps shutting down strip the system down to see that other things are not shorting out the PSU power bus,  pull all things connected to the MOBO, (we call them LOADS) all but the CPU and 1 stick of RAM, can be pulled, all drive cables too.
  • In all cases here, look for beep codes and Keyboard LED Blink codes.  (the BIOS maker or HP documents these)
  • The DT can have other cards inserted ,  into any PCI slots, remove them as a test, but not the VGA card if its your only VGA port is all you have. (or swap it with a good card, sure)
  • The DT has RAM sticks (DMM,DDRn) remove them and put back 1 at a time, using only bank 00 slot. Most times 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)
  • The CPU heat sink fan can be ok but the thermal compound under it failed, I've seen many do this , and the compound is rock hard now and  cacked like an egg.  Totally useless and overheats in seconds turned on.(CPUs go slower too hot and then stop)
  • If get this far, and all test show the MOBO is bad, then it is,  (rarely does  CPU go bad, for sure with a working fan)  and all memory sticks fail.  Bad mobo, sorry this happened to you.

Resets lets do resets now... there are only 3 resets.
  1. Go to BIOS screens as the screen told you,(ESC key) and push the key marked, RESET to factory BIOS settings.
  2. Pull the line cord from PC to wall power AC,  Push the power button, hear fans run for 1sec and die, this  drains dead  the charges on the systems large capacitors.  Wait 5minutes and turn back on the PC to test it.
  3. Same as above ,#2 but pull the coin cell, (best is to replace it if no voltmeter is in your shop) then let the PC sit for 15min to 1hour.  This will get remaining caps discharged. , Ok put it all back now and  retest it.
Do not flash your BIOS, or risk Bricking it.

BIOS works now: good. now:
I grab my trusty Knoppix disk (or stick) and test the system and HDD/SSD with Knoppix
The tests are does Linux run ok, does the DISK tests  and S.M.A.R.T pass, does the full HDD test there work.
Yes, and yes and yes?, then that  takes us now to BAD WINDOWS.
My BIOS allows me to boot to 4+ things, USB sticks, 2 hard drive, sdram slot or dvd. The F9 key does this,  I insert a CD/DVD or stick and boot to Linux in seconds, gee the PC RUNS GREAT, all like 5 minutes work .
On the GOOD HP PC we hammer the F11 key to fix dead windows as the HP web site clearly tells you how.  (the book to read is the big one called service.) F11 is hit at power on fast and tapped....
If any F11 restore mode fails for many  reasons like , HDD bad, or replaced before, or the current HDD has corrupted files cause say by a virus attack. (or kids playing , lets kill moms,  recovery partition just for fun)
These facts are why we test the HDD extensively first. (BIOS HDD tests are rudimentary but if fails ,BINGO)
If the new HDD was installed we now see F11 is dead, (normal that) then get the HP media kit from HP now.
If the PC blue screens of death happen that is a whole other matter.
IF the windows login screens are missing or locked up, use the F11 key as HP intended to correct that, click the startup files fix first if that fails do a full HP Windows install.
If F11 is dead,  and no HP media kits in your hands , that leaves using Microsoft disks and the horror of losing critical drivers and all HP apps GONE. ( it says that in the HP restore manual read that yet.?)
and desktops, dead and black screens.


LAPTOP black screens of death: (LT)
The laptop moves the screen inside, making it much harder to test. 
The goal, just like above is getting BIOS working and alive and presenting Screens.)
You are here if the screen never ever shows text , nor the HP  BIOS logo or COMPAQ logo. (it BIOS works with hot keys on demand this page below  is the wrong page, hit the home icon above or your back button)
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 ,nah we won't go there...)
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.  SEE LT DIPLAY TESTS HERE
Here is a list of tests and failure modes.  (power failing tops my list and the 2 ways to get that and more)
  1. Overheat PC,  will not boot, if it overheats too fast.
  2. The the main huge battery is bad, take it out until we make progress, Below.  If the PC fans now go dead the AC pack is dead. (in most cases never all, shorts happen!)
  3. Again  the COIN Cell is bad.( on the LT it's wrapped in heatshrink plastic )
  4. 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, below 18.5 is bad pack (or shorts inside PC) buy a new $15 pack.?)
  5. 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.
  6. 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(my hot keys even work even under BIOS alone)
  7. Many a  LT ,you have the VGA jack above and others, as per, and HDMI jack to do tests for Display data.
  8. If the external screen  works now only, then that means the internal screen is bad., or the CCFL is dead.  (see monitor/screen tests here , Laptop)
  9. BEEP CODES:"  The  LT that BEEPS or Blinks secret codes on the keyboard  LEDs on top of the laptop. Tells you what is failing, on mine it Blinkses the Caps Lock LED, keys.  Kinda like MORSE code, but not.
  10. 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
Some LT (poor grade) have the 19vdc coax jack soldered direct to the MOBO, and all fail evereone does. This is bad news.  (fixing it can be very hard work and  special tools)
This page only covers dead BIOS, screens 100% dead of yours is not dead that way hit  HOME above or the back button and fix WINDOWS is dead .

The Below shows how to strip a Laptop to find shorted modules or bad memory sticks, etc.
Things in electronics can be:
  • Dead
  • Good
  • overheating
  • loose.
  • shorted (when the happens power regulators shut down kill some or all things that compute, including BIOS)
  • or intermittent.
The rule is, power is first, no power no joy.  (taught in every electronics school from day 1, forever)
No power no BIOS. and always black (true black) screens and zero text. ever.

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

HOTKEYS:
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 (a Torch? in UK) 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,  Blink codes,  or BEEP codes, newer PCs use Blink codes and HP tops this list. ....
See my Blink Beep page.

 

Ok,  more tests , deeper!
MORE EXAMPLES :
Laptop Case top off. " DC POWER" checks:   A LAPTOP.
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 19vdc power  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 Blink 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 Blink 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 Blink 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 Blink 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 Blink 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 HP.com 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)

  (all) A short History and lots of tests and cures.  See all monitor issues , here.

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)



If only the external  monitor is dead, read this page on Laptops  for all montor issues go here.
Logic way to diagnose black screens. (I will do jumps here to solve the problem) My attempt to make the shortest list here. (above arefull detailed checks)
(Ill assume you are not standing in the sun, or the screen is dim or the screen has words (words there means it's not black )   Dim screens are caused by ,  these things.
If the PC beeps or Blinks, Cap locks keys, stop now and learn what those mean, first. (it is telling what is wrong, and only HP books cover this....period)
  1. If a laptop , does the flashlight trick work? seen here (if this test passes the LCD black lamp is dead, the PC  is not dead)
  2. No, it is a Desktop so does the OSD screens work seen here.? if not the monitor is toasted. (end story) If a spare monitor works then the PC is  ok, and monitor is not. THE OSD must work,.
  3. If a laptop ? does taking out the main huge battery cure the black screen issue? yes, replace it, if not, continue on.
  4. Are all  BIOS screens dead, too?   No, then this is not a black screen PC is it, its a NO BOOT PC, and that is solved here.
  5. Ok BIOS is 100% dead, no HP/COMPAQ Logo or text telling you to hit ESC to enter setup (hp BIOS).  The flashlight trick also fails to show data of any kind in step 1 or step 2 fails above.
  6. All screens fail, even test screens on DT or LP rear VGA port.  Then we work a dead PC base. (desktop case or that which hides under the Laptop)
  7. The Laptop we check for 19vdc into the mobo now using any voltmeter,  the A/C POWER PACK must be good . if not?, try a new power pack now.
  8. In all PCs are the fans dead? or packed full of lint and jammed.
  9. The Destop PSU is dead if the fans are all dead,  PSU fan , CPU fan and if  fitted, GPU fan.  DEAD PSU's happen.
  10. Ok the PSU seems to work.  the DVD enject button works, the
  11. On desktops we have 2 VGA jacks (or DVI or mix) one is Mobo jack and other (optional) is the PCI Video card, are both dead, even pulling the PCI card now and testing the mobo VGA is wise , now,  or putting in a spare VGA card in the PCI slot to test this path.
  12. Ok still dead screens.  Pull all RAM and try each stick 1 at a time.
  13. I now pull everything off the MOBO , (except CPU, 1 ram,  one VGA port  but I can pull the DVD cables and hdd cables for sure. On laptop top, pull all devices like that and more, NIC cards, etc.
The Key tests: listed again.  KEY EVIDENCE !
  • Beep or blink codes.  count the learn the code, write it down and read the HP service guide on you PC for the causes. (keep in mind weak power can make the codes lie ! or any shorted modules inside, that cause weak power)
  • The screen really is black even when BIOS hot keys are used !
  • The flashlight trick works or not, on all CCFL screens made,  2010 or older mostly.
  • Fans dead or packed in lint.  all fans, desktops have more fans all must be watched, and inspected.!
  • HDD is silient. 100% no noise from it will not cause black screens ever, but will cause DEAD OS, (dead windows for sure) (please do not try this on any SSD but Hibrids yes.
  • DVD (or CD) tray  button eject is dead.
  • On modern Desktops with high end mobo's my ASUS has a green PSU standby lamp if dead, means the PSU is dead, or line power A.C. is dead.
  • The Laptop runs with no battery. 
  • The Laptop runs with the correct 19vdc power pack. (not using power pack off other PC's)  65watts or more.
  • The PC runs (any) with module removed.  Yah ! parts can short. for sure.
  • Smoke coming out of PC, sure can happen, seen it vast times. For sure in PSU's (cheap)
  • If PC has 2 VGA jacks try both,  ? then try 1 VGA port with the PCI VGA card removed?
  • If fitted with VGA PCI card did the AUX power jacks fall off. seen here.
To test any PC and all the above fails. we strip it down to near nothing to find shorted modules of ANY KIND. Laptops.
Desktop  too, even to the point of bench testing them , called a minimum system.
(with)
MOBO + PSU, + power botton + CPU(with working fan)+ 1 stick of good ram (DDRn) in bank-0 !
Then 1 VGA card PCI.  (and swapped)
If you don't have a spare VGA card , PCI, buy one for like $5 used and keep it in your  spares box. (for testing)  Would you not be happy some day and the $5 saved a $300 labor bill?   yah..
Do not pull the 24pin power connector or power on botton,  the later can be pulled if you know what 2 pins to jump (poweron>ground)
With any VGA monitor connected the Screen must show BIOS screens (on demand)
A Bad CPU are rare, pins not bent. (fan works, and heatsink compound not like hard as nail dried glue)
see the VGA onboard here m5a78.  If VGA port is dead, add a VGA card in the PCI slot to see if you get SCREENS now.

MIN, System. photo next.
Found on the net this , nice photo  One stick of good RAM is necessary,  A case is optional . The VGA card is optional if you have  mobo like the above shows.
  No mouse or keyboard need to see the Post Screens, "hit any key to enter Setup" (HP BIOS)
This next drawing shows, (only on ASUS) the power pins to jump oif you don't have  a power switch,handy, with a screwdriver tip jump PWR to Ground next to it, do not hit the +5vdc pin ever.






Be happy you don't have this, circa 1981 IBM. A BLAST from THE PAST ! first PC 8088 (intel, with BIOS 24p ROMs ) All TTL logic seen here was replace with GLUE logic in the future. (at vastly less cost)






Version 6.  5-9-2017  ( a work in progress)  I'm retired but not dead.  By : DeadPool.  ,  the word flash is now used only for Flshing BIOS and BLINKS are LED binking....(not mixed as before)