Desktop Display Monitor tests and diagnosis          

VGA/HDMI/DVI/DP external monitor displays only.  Click home for other choices like Laptop PC's.)
(test the offending monitor Other Desktops or on Laptops with VGA jacks, or HDMI to a TV) Fast checks here?

Do this or the baseline below: If the screen is dead on 2 PCs or more then the screen is now DEAD. (he's dead jim)
A Baseline dead Monitor test, and needs no working PC to do that, even disconnect the PC video cable (all kinds)
  • Power on the monitor and the power button light glows, if not power supply inside is dead. (AC power cord not loose , missing or any AC power strip dead, use wall jack power only now)
  • The monitor has its own brain and its own splash logo, so in 15 seconds or less push the MENU button on the monitor. This will show the OSD pop up menu, if splash dead or OSD is dead this is a DEAD MONITOR.
  • if not dead the monitor tells you on its screen , nosync, nosig, no signal, no connections , out of range,  if yes the monitor is 99% good to go.  It surely is not dead is it.
  • no connect monitor to PC (if PC has GPU card you must connect to that port only) then using the OSD screen set the port used, to the one you are using,  if using DVI, port 1, set it to DVI#1 now turn on PC.
The monitor must work and show the PCs splash and the BIOS keys and BIOS screens all work now.
Old monitors love to fail, 2010 and older and fail the first  steps above,  for   bad CCLF backlamps lamps.
If your new GPU card , test the base ports of the motherboard, with no GPU card inserted,

If the PC is locked up in sleep mode that is not a monitor problem at all, that is bad drivers on the PC. If you do not like sleep modes turn them off,

Relic Monitor issues.
Skipping past Cathode ray tubes all old 2000 or older displays as of 2010 all are  LCD (+LED back lamped) flat screens (most are, I am skipping OELD and Plasma screens too, mostly Plasma is DOA now.)

Monitors have  many types of  failure modes,  including failure to sleep, caused by bad cables, bad  drivers in PC or using new PC on monitor older than 2007 (eDID began then)
Plug and play eDID,can fail for these reasons.
The video cables or power cable to the monitor loose or fell off, or tripped on and now broken or pins smashed, end to end.
Most monitors  have 1 or 2 LEDs or just the one inside the Power button on said monitor.
Many monitors have yellow(amber) or GREEN STATUS LED here.
The amber glowing can mean the monitor is sleeping, if flashing it can mean , all inputs channels are dead. (only your monitors users manual covers the truth here)
The older monitors (2000 to 2010?) sure can go to crazy and wild  self induced sleep (OSD TIMER), and tells you that if you watch the screen so turn that off that first.
One guy has a  monitor with an AC/DC power LINE  pack and was the wrong pack plugged in. oops. (looks like some laptop power packs or you mixed up your packs)
This monitor can fail just like laptops do to cracked screens or CCLF going bad or the inverter on the  main power board failing as seen here. (the data board inside can do dead too)

Next is  MONITOR Power on Tests. (long play)
  • AC cord attached to wall AC jack and to monitor.
  • I push the monitor power button and you will get a makers splash LOGO  and the Energy star logo, or both like this.
  • This pop up logo will last for 10-60 seconds and then shows "going to sleep" (PC missing or off or in sleep mode)  If this logo and message above is missing or looks ugly the monitor is toast (bad)
  • If  good PC is running connected up the OSD menu, if the botton works ok on the front of the monitor. Like seen below.? That is good sign of good, do more testing.
  • The error messages can show many error missages , Like No signal. (and if true the PC video cable is dead, only why remains)
  • You can power on 10 times and see the same clear logo, even if the no PC present. (if not? that is a bad monitor)
  • The processor brain inside the monitor, wants to see good and legal sync signals before going to full operation, with full video presentation.
The Power button light (LED) on some monitors have 2 or 3 colors. 
Amber, = sleep mode. (usually only after 10 seconds see this or PC goes to sleep mode or hibernate mode)
White/blue/green = all mean power ok.
Black = , no AC power present ,or not turned on, or power supply inside monitor is burned out. (a bad monitor)
The Desktop external monitor powers on and will always show a logo "its OEM LOGO" ,  or some makers logo then "Energy Star (very common in USA) then shows errors. My desktop Shows "Viewsonic"
Now some monitor detected and presented errors: (PC on )
  • "NO SYNC" errors.  means the horz/vertical sync lines in the cable are dead. (PC issues)
  • "NO signal" means  1or both Video lines in cable are dead. (PC issues)
  • "No connection" errors means all  video lines are dead, in the cable. (PC video dead) (do have the wrong port selected in the OSD settings? match PC connection?
  • OUT OF RANGE (means you connected  new PC to a relic monitor, and the resolution is set to and illegal RANGE. (TRY 800X600 resolution and work up from there or read the screens spec)
  • Screen OSD locked, push the menu button for 10 seconds, now it unlocks.
  • Old monitors had internal sleep timer or sleep clock,  best is to hit the  OSD menu button  and turn OFF POWER_SAFER mode or timer. (Sleep timer off)
  • Screen scans below failed? Mine show live,  VGA/DVI/HDMI,DP  port scans , if all 4 are dead, it tells you that and goes to sleep. (in 10 to 60 seconds, (varies by makers model, mine is adjustable to 60)
Old (pre year  2000) monitors go dead, go dim , go yellow tinged, go intermittant or strobe. (CCLF back lamps are mostly all dead now)

(The On Screen Display) OSD,   Below are examples. of monitors not really dead.
What happens as the Monitor is turned on?
Well it too has a brain inide and it does self checks inside then puts up a makers logo icon (Dell , HP or Viewsonic) then scans up to 1 to 5 video input ports for live video inputs that are valid.
If it sees 2 inputs live, one is predomenent. (only your manual tells you this sceret order)
If the silly PC failed to read the eDID data , it might pick and illegal screen resolution, and will be odd locking or the monitor shows "OUT OF RANGE" (means Illegal too high resolution used)
Learn that modern monitors and same desktops can in fact change brightness on the Windows side and does to by the PC talking to the eDID chip, and can be over-ridden in the menu below.

Normally the  monitor will show the PC data presentations of the booting OS or will show an  error. (  if no monitor errors POP next is PC POST errors if any and last Windows errors if any.... the boot process...)
If the PC is dead, (shows NO  sync the monitor can turn off)  Monitors  have at least 2 levels of power, ON, sleep mode or off) seen here.
The OSD menu key on the monitor face bezel  always works if the PC is working right.
If the PC is dead (truly) or only lost video, the OSD runs and works about 10 seconds long, (up to 1min) and is to prevent LCD burn damage with a static, OSD menu forever.  On some new monitors the OSD floats around the screen.
Each monitor has its own rules, some will not allow OSD button to work until the PC video starts working.
I can not show all (VAST)  monitor screens here, but OSD screens are mostly boring and simple and near the same.
The only trick is some monitors flat refuse to OSD present if he PC is dead. Some do , Some do not. (but if the PC is dead, all monitors tell you that, "NO SIGNAL on all cables"
My Viewsonic the OSD manu, and key marked the same,  is dead if the DVI cable is unplugged, but if I turn the monitor on, I get the LOGO and then NO signal , then a black screen. (this is all normal)
I am pressing the monitor bezel Menu button key, now:
OSD 1, On screen Display. PC is working 100% here.

 No signal means the PC is not sending signals to the monitor , then goes to black screen.

A short history of Monitors is simple, 1987(PS/2)  CRT's then 2000 year LCD +CCFL then LCD +LED (2010 year) and last OLED panels), 
Time lines:
LCD+LED , started on the wide screens year 2010. (it took industry 7 years to start using CREE bright white, LEDs,  super expensive)
CRTs ended when LCD hit the shelfs , in year 2003.( they CRTs out sold  LCD for about 7  years due mostly from very high bright white LED prices $1 each, wow.)
The CCLF' short life tubes ending about year 2010.  So there are 7 years of these lame old CCLF monitors(and laptops) still being used, that all turn yellow then die.
How to avoid buying junk PCs and monitors with CCFL (easy buy 2010 or newer) The HP history is here (partial)

Links to read as appropriate to your technology: (years )

Top fails: (first are old screens, with CCLF)
The dead CCFL makes the Screen black and OSD dead.
The CCFL can be  dead, dim, yellow for pure white , intermittant or strobing effects (disco like) Best is to retire this junk the costs of parts and labor are 2 to 10 times what the monitor is worth.
A new screen is like $100 and used good monitor is $40 add labor and you go broke.

Monitors stand alone tests, with no  PC connected, no VGA, no DVI no HTML cables attached, example HP LE2002x .
Also learn that many newer monitors not connected to a PC go in to automatic self test mode,  let it and watch what it does, for sure when new to learn this and what it looks like.
You power on the monitor and it  shows, this or the monitor is dead.  The red words below show scanning port that shows no signal. All 100 % normal. for 2 dead or missing cables (this photo is missing cables x2)
   This shows and times out, and then sleeps.(by self)
HP OSD MAIN menu, what you see after pushing the menu button.

If the PC runs you can get there via OSD menu button and crank up the brightness, some displays have dedicated buttons for just that.
Some displays have  built in test pattern , nice to see if the colors are looking ok.
Old monitors have this old school malarkey, timers and what not. Turn it off and then only use the PC side for sleep mode. (if at all) Not Energy Star but Energy-DERP.
WARNING if you do the factory reset seen in main above, all this timer junk goes active, again.(pain)
This below are relic monitors, all this odd timer jive is gone now. forever.  and a Pain if on.

The below should clear, that you need to turn off the stinking rotten SLEEP timer here this be first to check. 2001 to 2010 super common to see this.
I am pressing the monitor bezel Menu button key, now: This is calld OSD< for on screen display. (the monitors brain does this , never the PC)
Just turn it off. 3 click here.

If the menu button goes dead, hold menu buttion for 10 seconds and it unlocks.
On more legacy oddity is windows screen saver and you sure can turn that on, and even pick black screens , but ends at a touch of the mouse. (USB ports not in sleep mode sure)

Finding the problem and fix it :  (do not read this , this is only how very old montors work, this is for the rabid curious)
Top failure modes:  (the fast quick tests are here)  this section here is for total screen death , no words , no text no logo's no errors are on the screen ever.
If the monitor is  ok it  shows logos or words  but the PC is dead (you saw "no signal errors" for 3 seconded turned on) then  See black screens here.

Desktop: DT monitors   (when I say VGA port or cable , it means  that or DVI or HDMI what ever you have connected for video to this monitor)
Steps to take for diagnosis:
  1. Plug the monitors power pack in, and turn the monitor , the HP  (or you makers) LOGO must show up and  no signal waring for about 3 seconds or the monitor is bad. (jump to #4 below if this fails)
  2. Connect the monitor under test to a known working PC, turn on the monitor then the PC, the OSD screen can be commanded on with the front panel Monitor menu key.
  3. The display LCD-CCFL is dead , dim, yellow or weak, or its PS_inverter and do the flashlight check
  4. You Error no signal The VGA cable  can be bad, replace it or try a spare barrowed?   (you get this error even with monitor tried on other PCs)
  5. The monitor may also show ("Going to sleep" mode or "power saver mode" in most cause this is the PC messing up.
  6. The older monitors have inside the OSD of the monitor, "Sleep timer, in fact turn off all timers found inside any OSD menu" look carefully some times there are 2 timers or some clock"
  7. The monitor is always best tested on a known working PC of any kind with a VGA jack (15pins) Dshell connector on its rear,  that many have, or if DVI cable /port monitor the same. (or HDMI if fitted)
  8. If the monitor has HDMI port you can test this on your TV. (HDMI cable used)
A good monitor will show the makers logo and no signal error each time the monitor is turned on, PC turned off.   If the monitor is dead look here for REFURB  monitors.
The HP logo and errors seen here, (no sig) are from the Desktop monitors internal Brain.  (not the PC)
Please note that monitors have there own brain (see MCU below? yes a brain processor crude) this brain will show thee status of the main video ports.
RGB = red green blue video, H = horiz. sync, V= Vertical Sync.. this old dog below uses CCLF back lamps.(600volts too or more)

Here is a list of symptoms. and tests and cures if possible.
  • Monitor Power lamp dead,  if amber that is sleep mode or bad power supply inside or outside power pack, dead, or you tripped on the AC line cord?
  • No sign on messages or text or logos ever, that is a dead monitor. (RIP) or not really plugged in to power (reseat all connections)
  • Goes to sleep by it's self even with PC not in sleep mode, turn off the sleep timer using the monitors OSD menu button.
  • Lines on the screen see this. (see the twist test there)
  • Dim, or yellow yellow (with say white notepad program runnning) the CCFL background lamps are bad. (or the lamps go dead randomly or blink oddly disco like strobing effect)
  • Shows going to sleep mode, It is (turn it off same way as next line shows)
  • Shows no Signal or no SIG or no SYNC errors the PC is dead or went into hibernate mode, cure, is turn that off in the PC using control  panel, Power OPTIONS below:
  • Shows error OUT OF RANGE means PC RESOLUTION is set too high for this very old monitor, try 800x600 at the PC settings. (always caused by eDID data chip read errors)
  • Monitor turns itself off, make sure the monitor is not set inside for a sleep timer. (see OSD menu and see all timers inside and disable them all, if power goes off, the monitor is  bad.
  • Does the monitor fail on 2 PCs/ if  yes, then the monitor is bad.

Presentation mode at the PC END, is the best testing  mode for any suspected bad monitor.
The answer to sleep modes wrong is here on one page.
This  is what I do, and if this fails the drivers are bad. (even just as a simple test to force sleep OFF)
Win 10, 64bit v1903+

Dead monitors for dummies
  • Power button dead and for sure, power on Logo of monitor maker does not show up, that is a bad monitor, (or bad power cable, super rare, but if power pack yes or wrong pack used)
  • Monitor fails on 2nd PC, bad monitor
  • 2 Monitors fail in 1 PC,  that is a bad PC. (see why)
  • Monitor turns on but the OSD menus work but are ugly looking , that is a  bad monitor.
  • Monitor told you one of four errors here, that means the PC is sick or cable bad to it. PC sick click see why above. 
  • Monitor keeps going to sleep , turn off sleep timer in OSD screen, (if it has one) and in the PC seen here.

Failure to Sleep when wanted:  Just a bad GPU video jack or  cable can caused this failure or using modern Monitor on very very old PC or the reverse. ( the cure are 2010 or newer monitors for all PCs)
All PCs talk (commincates) with the eDID chip in side the monitor, call it the Plug and Play identification chip (can some can set brightess too remotely)
This chip if dead (simple bad cable can do that or bent pins on the end of said cable. on both ends.) the PC can not learn what is connected at all. Impossible.
(The PC as it boots up talks to the chip and can have a  eDID signaling failure)
(Applies to Sleep/ Hibernate/ Hybrid modes when I say sleep)
 Some new monitors have 3 levels deep of sleep, even to say 3 watts power or less. (some PC take 15 to 30 seconds to recover from the most deep sleep modes)
  • If the drivers for your Video GPU card or onboard GPU chip drivers are wrong or missing or corrupted, sleep will fail.
  • The video card can be just no good, and has bugs not supporting full sleep modes.
  • Or you have SLEEP MODE  turned off in Control Panel (Power settings)
  • The Video Cable is bad, be that VGA/DVI/DP, HDMI ,etc.  Or bought from fleabay dirt cheap and is not eDID certified. (missing 1 of 3 key pins)
  • That Video cable is too long; a cable over 30 meters. (not likely, but must be said) The eDID uses IC comm's, and the signals must be clean. (if the PC has 2 grounds and if different from the monitor ,eDID can fail)
  •  or it missing eDID pins or wiring that allows eDID to function plug and play fails and so will sleep.
  • Using a New PC with a Relic monitor. (or the reverse, OLD PC on a new monitor) both ends must be eDID functional to work right.  (below year 2007, monitors, with newer PC expect trouble.)
  • If some old CRT monitor sure it fails. Most old pre-2010 year, LCD monitors are dead now, due to dead CCFL background lamps.
  • HDMI can fail if the 2 sync pins fail. Or uses CEC controls(HDMI)
  • If you run modern PC with modern monitors,expect no problems at all with hardware, only drivers fail during OS upgrades are the prime cause.
The eDID tells the PC what the monitor can do,  then the PC uses this logic to control power and sleep.
Learn that many video cards go off line if any of 2 failures happen. This fools some folks in to thinking stuck in sleep mode, and is not anything to do with that.
1: The eDID is dead.
2: Any of the 3 video lines RGB ,  are not drawing current (means line cut) or too much current (CARD DAMAGE protections)
3: All monitors made (the monitor brain inside) even warned you "no signals , going to sleep mode now " this is just the monitor going to sleep even if the PC IS DEAD, why burn power with a dead PC says, ENERGY STAR GOD's.

DPMS modes ( wiki)  this magic saved us from adding new pins.
VGA and DVI analog modes only.
As you can see if either sync line, or cable wires same or pins cut or bent,then the monitor shuts down.
In fact it will tell you going to sleep mode or only cable was unpugged. (and  it for sure does not know why , only that  the 1 or 2 wires went dead. (PC dead or in sleep or bad cable)
I will not ever cover digital modes,  like DP or HDMI, you can learn those by googling or using the wiki first.
Power modes change by the lack of sync, and the may turn off with no sync or just text you to the screen , all input cables dead.
Each connector and its rules of usage are vastly and radically different from old analog video to full blown digital display data methods.  (New PCs are DP and 4k ready end to end)
As you can see there are lots of Video or graphic sports. for 3 full decades now.  (VGA is now going byebye forever) Most new PCs may have 2 ports, DP and HDMI, (HDMI for TV is still popular)
There are adapters that can just about any conversion.
JACKS so many JACKs (connectors all standard)

version 2.  12-9-2017 , 5/7/2019 (sleep mode problems)