Desktop Monitor tests and diagnosis          

VGA/HDMI/DVI/DP external monitor displays. (test it on desktops or on Laptops with VGA jacks,or HDMI to a TV) Fast checks here?

Skipping past Cathode ray tubes all displays now are LCD flat screens (most are, I am skipping OELD and Plasma screens)
The checks are easy for most hard failures here.
Monitor have  many types of  failure modes, but sleep is feature, not  a failure.
Your  PC can not turn off any external monitor,  (power lamp goes off black dead) only amber power for sleep and hibernate modes and if you watch the screen , it tells you "going to sleep or  warning"
The word "off" , is very odd word now, off now means (lowest possible current and watts, not zero)

Or the act of unplugging the VGA/DVI,HDMI, DP, cables will cause  all monitors to go to sleep, even tells you that. (my View sonic, DVI shows, "NO SIGNAL" doing that, clear as day.)
The older monitors (2000 to 2010?) sure can go to self induced sleep (OSD TIMER), and tells you that if you watch the screen so turn that off that first.

AC power cord (or power pack) fully seated both ends and the AC wall jack is known to be hot and good, use  desk lamp to check AC power jacks of any kind. (hot means live 120vac 60Hz line service power)
Does the Monitor fail on 2 PC's for sure one known to be good PC? yes/no;  if yes, try a new VGA cable, still bad this is a bad monitor. (I can assume you  know where brightness knobs or OSD setting are?)
This monitor can fail just like laptops do for 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)
The CCFL lamps inside can go dim, turn yellow, go dead, or be intermittent. (2010 and older only)
Next is Power on Tests.
  • I push the power button and you will get a makers LOGO  and the Energy star logo, or both like this.
  • This pop up logo will last for 10-30 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 OSD menu and deep settings inside may not be accessible until the PC is working and connected. (this is to prevent screen damage)
  • 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 have 3 colors. (HP has this)
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 + power light dead, means monitor is off or dead monitor. (not really a color black, but you know what I mean.
The Desktop external monitor powers on and will always show a logo "HP" ,  or some makers logo then "Energy Star (very common in USA) then shows errors. My desktop LCK shows "Viewsonic"
  • "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 lines are dead, in the cable. (PC video dead)
  • 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)
You turn on the monitor and then promptly goes black?  If true the PC is dead, or is locked in sleep mode, or the VGA/DVI/etc cable is bad , missing .
 (if 2 monitors fail on one PC the PC has issues, or later or see this (or the reverse monitor fails on all PCs)
This will be normal actions with a dead PC, but in all cases the monitor will show, no signal if the PC is fully on first, and the monitor last. (the monitor tells you, and error, NO SIGNAL,etc)
The cable has 5 key/ pins and wires,  Horz. / vertical sync and RGB if any line is dead the monitor will tell you or if just the 2 sync pins fail, if both sync pins fail, the monitor goes to sleep mode.
The OSD menu  button goes dead with NO SYNC. and is normal  (this may be to protect the screen for static burn in  damage if the OSD was left glowing endlessly, with a dead PC and the below menu's glowing for ever..)
(The On Screen Display) OSD,  best is to power on the PC first, then the monitor for best displayed infomation. 
What happens as the Monitor is turned on that way is:
The monitor shows a HP logo first, a graphic (or others if is another brand, like the great monitors made by Viewsonic that I use)
Normally the  monitor will show the PC data presentations of the booting OS or will show an  error. ( a monitor error, or if ok, the maybe the OS boot screen errors)
If the PC is dead, (means no video or sync) the monitor tells you this fact, clear as day, see below. (or only tells you for 2 -3 seconds only) << repeat the power on of the monitor to see errors again.
The menu key on the monitor always works if the PC is working right, but the menu key can be dead, (or runs only for 1 second)
My HP LE2000x monitor (LED) will not show the OSD on demand if the PC is dead.  (some models it will  for only short time, with a PC dead the VGA cable (or DVI) unplugged)
I can not show all 10,000 + monitor screens here but OSD screens are mostly boring and simple and near the same.
My Viewsonic the OSD 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)
OSD 1, On screen Display.

 No signal means the PC is not sending signals to the monitor , then goes to black screen.
SPEEP issues problems and facts:
On old monitors the monitor had its own SLEEP feature  and timer, (turn it off in the OSD) This feature has no usage now on any modern PC, ever.! Kill it dead inside the monitor now.
Long ago the  VESA standards added PC commanded 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.
If VGA vertical or Horizontal sync pins of they go dead, the monitor texts error (no signal, no sync or going to sleep){or if PC Hibernates}

The 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,  Cost factors were it)
CRTs ended when LCD hit the shelfs , in year 2003.( they outsold CRT then, but the price was still too high)
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)
If the lamp is dead, in most cases the owner throws the monitor away due to a new display is a fraction of any possible repair bill.... (econ101) proof below.
 Walmart has  nice $50 display for sale, why not upgrade to LED display now.?
If the flashlight test fails on the monitor , and no power on logo messages seen like below.,   , nor errors seen or on monitor screen or text ever,  turned on , then the monitor is bad.

If the monitor tests ok ,but the PC is bad see here, Black screens of death.

Monitors stand alone tests, with no  PC connected, no VGA, no DVI no HTML cables attached, example HP LE2002x .
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.
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)

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 :
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 lamps.

Here is a list of symptoms. and tests and cures if possible.
  • Power lamp dead,  if amber that is sleep mode
  • 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 (click this there)
  • Shows error OUTOF RANGE means PC RESOLUTION is set too high for this very old monitor, try 800x600 at the PC settings.
  • Monitor turns itself off, make sure the monitor is not set inside to turn off or spleep. (see OSD menu and see all timers inside and disable them all, if power goes off, the monitor is  bad.

Presentation mode at the PC END, is the best testing  mode for any suspected bad monitor.
Turning off sleep can be easy or hard, depends on how your PC was setup new and if PRO grade windows.
The Windows control panel , under POWER, setup custom power profile, with your  name.
Then see everything there to NEVER.  see first photo below.
or if this fails.
  1. Try power options first. See photo. this works for me.
  2. Windows Mobility Center but loves to fail on Desktops and all Windows HOME versions (it's DEAD).
  3. Use your your screen saver in a way to prevent sleep. (google this)
  4. Uses powercfg  command line utility turn it off.  See my batch file nosleep.bat,  run it? (edit it to see  it is safe and IS)
  5. In windows PRO, you can use the GPedit  and turn all things there off. (Group policy editor)
  6. The Don't sleep program works good.
  7. Put the PC in to Kiosk mode.
  8. Run a top bench mark program that runs DISPLAY bench marks, that keeps the GPU super busy, for testing monitors. (I use PASSMARK Performance)

This is where you setup custom Control Panel  POWER settings. (use your name ,profile1? ) and turn all 9 catagories off,  Display set to never off, and sleep disabled.


This works on Laptops and fails on desktops.
I have windows 10 Pro, on  a gaming desktop Z270 build and the box above Presentation settings is missing  and expected missing battery too.  So is DOA on a powerful PC. 
MS  clearly hates desktops. (even "ALL_in _One desktops" with no battery anywhere, fails here, wow !!! way to go MS.

I miss  XP.  always on  or presentation mode. )

  The golden days of easy presentation. (on any PC made)  Why in the world delete this mode? MS !

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.

version 1.  12-9-2017