HP  BIOS P.O.S.T BEEP ERROR CODES  (power on self tests!)
Keyboard LED BLINK or CAPS lock blink error codes.                         

Some PCs blink and beep the same codes at the same time.
Always step one ,  if and HP locks up, is th   standard HP long  ReSet,

HP like all other PC makers used vast numbers of different BIOS versions and vast numbers of beep codes and bink codes.
From the year 2000 to now (2018) 18 years of codes.
HP built there BIOS by contract for years, from AMI and Award  and later Phoenix™ merged with Award™  and later still HP has HP BIOS, (there own)  )
HP also in some wild horror decides to not cover these codes in there offical service and maintence manuals,  go figure that.
They do have it , but is buried deep in the HP piles and piles of documents. (some are even lost.) Google BIOS Central and get lost for eternity.
The number one all time failure of BIOS or for error codes is the dead RTC coin cell battery,  in your PC,  a 3 volt tiny battery that when dead makes BIOS GO NUTS ! See mine?
he tiny battery lasts 5 to 7 years (avg.) Stated clearly by the Coppertop maker and the pink bunny. (data sheets, don't lie)
Never ever try to understand nuts,  replace the battery first. and win ! $3 cost. or test it. The PC can even go DEAD  with a dead RTC battery.
RTC means , real time clock , chip, and also means the NVRAM is dead too now. A.K.A CMOS RAM, dead.

What matters most are 2 things,  what PC? and what year?
For sure year tops the list. (after all HP had a penchant for changing BIOS every year, not just to add new features, no,  change things just for kicks , like error codes, dang me.)
Learn now that the POST brain is not magic nor artificial intelligence, in fact it's dump stupid intelligence. It is not Space Odyssey HAL9000 yet,  sorry maybe in the year 2050...? The tests are all RUDIMENTARY.
That means take the POST error with  a grain of salt.   (and learn the fine art of stripping PC down to near nothing to ISOLATE PROBLEMS !)
Never ever believe  the BIOS Flash ROM CHIP is bad, no it is NOT bad, they last 100 years, as does the code inside last that long, by design (have proof) not withstanding lightning damage or some kid ESD zapping the poor chip messing with it with no ESD wrist strap grounded in the proper way.

The first thing to do is remove the main laptop battery and leave it out until the PC runs right again. Next is the RTC coin cell get it the H3LL out of there! (a new one) (I've seen 3 month old cheap china cloned coins cells fail new)
Learn that when it says the CPU is bad 99% of the time its telling you a lie,  this is because no PC on earth can test it's CPU ever. (not at POST TIME)
Maybe HP could show, "I'm having trouble processing, for Unknown reasons" not CPU bad, (inane to the nth degree that)
The CPU can seem to fail for many reasons totally unrelated to the CPU , like power failures, (DC power and noise there) or address or data or control line, errors, all unrelated to the CPU. (facts all)
Even bad RAM can make CPU seem to fail after all , no CPU here can run tests, with no RAM can it.?  NO !  Try 1 DDR RAM stick at a time  in bank 0 slot.
See all those vast numbers of chips on the mother board, guess how many there, can cause  the CPU to stop processing correctly,  ponder that for a moment.  (most or all is a good answer)

I will now organize my links below by years. It is not in order yet, maybe later....
  ( Read this HP main page for only modern PC's) (I see 2010 and older dropped now)

HP workstation ! XW4600  as will a great Z400 or  Z600 ! My favorite PC of all.

I made up a PDF of old codes uses here.
If the HP/COMPAQ is older than 2010.  see these caps lock blink codes.

BIOS 2015 and newer is here at HP. 

See me looking at what version on HP BIOS, SETUP VERSION; F.06

One more page on 2005 COMPAQ beep codes.(Some codes there only Klingons can understand, check out #9)

If you own a POST card, this works too. (a tool it is)
How to use a P.O.S.T card and see all BIOS check points.( and all errors)

In most cases you will never learn what the correct matching beep/blink codes are for your PC,  (takes hard work, to find and the older the PC the more work (2010 and older)

LEGACY: older than 2010: (seems nobody wants to support legacy PCs , HP calls them RETIRED & Legacy or FORGOTTEN !)
Retired means to them, gone, deleted, and we don't like talking about them; as most things about them we forgot 10 long years ago. ( like solderball failures 2008)

Other PC's with older BIOS: This section is on LEGACY PC's old and retired, and poor support at HP.
HP has this page on BLINK codes et cetera , covering  newer PC's. Before and after 2010.

The old codes are the most hard to dredge up. the .year 2000 .. See old Phoenix V4 book here. page 39(pdf page)
On super old PC , BIOS V4 one beep means I'M OK. "One short beep before boot" this means booting NOW.
Award 6 BIOS does a long beep and then sends messages to the screen.

Most PC 10 years or newer all do BLINK codes now.
Remember to see if codes (beep/blinks) are short or long, and do know they loop,  for example 2 blinks long delay, repeat, endlessly is code 2.
Amazing, HP new pages here , goes to 2011 only,  they removed links to older PCs

The beep codes became, and moved to the NUM/CAPS lock keys LED lamps Blinking codes.  (silence is golden?)

One more from the great year 2002,  COMPAQ OLD. (but sold from HP)
2003    D330/530 COMPAQ 2002-4)

2005 COMPAQ DC5100 desktop;(or any DC series)

One trick is knowning what HP calls this document, missing in the service manual, omg,  a Hardware Reference card.
I then search like this and find those documents, lost  in the main index of all HP PCs, on the support pages,  lost there.

I will and more below,as I find them (Legacy BIOS) below here.

2006 ---- DX2200 series

2005 DX/DC 7200 or 7600

2012  HP Z220 SFF, Z220 CMT, Z420, Z620,and Z820 Workstations

2003 Ze notebooks, n1000v seriies,1100,2100,2500 series..(pg 3-19)

2005 DX5150

DV7xxxxUS blink codes below:   (and DV6)

(in each case if the word BIOS is shown,  get a new COIN cell Battery HP RTC bettery) 

Please find the information you are looking for as shown below:

LED Blink 1 time : CPU not functional - Replace Processor (OR MAIN POWER IS WEAK, DC POWER OR EVEN RAM)

LED Blink 2 times : BIOS Corruption failure - Replace System board  BULL THE COIN CELL IS FIRST!

LED Blink 3 times : Memory error not functional - Replace Memory Module

LED Blink 4 times : Graphics controller not functional - Replace either System board or Graphics card

LED Blink 5 times : General System board failure - Replace System board

LED Blink 6 times : BIOS Authentication failure - Replace System board (COIN CELL BAD FIRST)

Finding them all proves hard and time consuming... I stop here.

Everyday less documents exist for old PC's
Over 10 years old, most owners of PC, send theirs to the recycle center.
After all why upgrade a $20 PC with $200 hard cash? or more.?  yah nobody does, so support ends after 10 years.

Laptops are like dogs.
So a 10 year old laptop is really 70 years old. (and full of filth inside and worse)

HP's new 2015+ blink codes here, nice that it does Desk and LAP tops in one. NEW UEFI rules. Watch out for NEW HP PC's with UEFI , that have over 10 BIOS upgrades before BIOS works right, (A PITA that)
TXT error = TET

This is  POST card, it will tell you the secret BIOS codes for the errors,  but you need the  book from the BIOS maker to understand the codes, some have 100 errors.
Mine shows 00 for OK.  On good boot

What the H3LL is beeping?, this ! it is called a Piezoelectric sonic beeper,  Replacing the COIN cell is a  GOOD 1st  MOVE !  The COIN can die at 5 years. (5-7 is average) 10 is upper end of the bath tub curve of life.
This is a DESK top, almost all DT look just like this. The coin holder can be flat or vertical. Walmart sells them in the WATCH department, center left, side of counter. 2032 cell below.
If the coin cell goes dead, BIOS goes NUTS.( and the time clock to called RTC)

HP DV7 coin steps, clear as day in the factory service manual.  RTM read the manual, get them before HP deletes them online after 10  years, keep the manual so you have it when things go bad.
Do not put the battery in upside down.
end DV7-xxxxUS laptops

ON some laptops  the coin cell is very very very hard to remove,(compaq era) near total disassembly needed, RTM. Read the manual , ok?

Last and not the least is to do a full HP MAGIC  reset,  This magic HP fix , resets,  PC stuck on sleep mode or hibernate or if chips latched up (CMOS old tricks)
Power off, unplug PSU power cords desktop or power packs (DT or LT)
If  a Laptop, the big battery main must  be removed now.
Now push the power button to discharge all cap inside the PC.   count to 10 seconds, then...release the button.
Wait time,  5min to  1hour; your call there, try to imagine electrons, draining off capacitors large.., now, they are!
Doing the above with a bad coin cell is a waste of time and energy.
Buy a voltmeter for $10 buxk,  heck go wild and spend $20 and measure the battery voltage on the coin cell, 2.9vdc means its dying , below this its bad, 3.3v is fresh battery.

I then go to BIOS screens, and push "reset BIOS to factory defaults"
It does just what it says. (no more) "this is resetting all BIOS  Settings, or configurations settings into the BIOS CMOS NVRAM BANK. (back to factory fress settings)

end topic POST CODES:

Last of all, lets say no more POST errors now,  but the screen is still black. (no text ever)why?

Lets say the monitor is dead, or the screen shows data with a flash light pointed at it, why did my 2010 and older screen die, well that it easy , all do that because the CCFL tubes are now dead, dim, yellow or intermittant

version 4.  first :6-4-2017 (2-15-2018 revison )