All LCD Screens older than 2010 had CCFL tubes inside for the backlamps. Almost all of them made then are dead now 8 years later. 20,000 hours is the designed life span. (yes SHORT)
NOW LEGACY HARDWARE....HELL.
CCFL are now legacy hardware. : "Cold Cathode Florescent Lamps" CCFL for short !
Monitor or Laptop SCREEN BACK LAMP failures (CCFL) are #1 failure rate items up to 2010 year when LED came on the market. (most die in 5 to 6 years)
Symptoms are all classic failure modes now:
CCFL fail in these modes: Dead, Dim, Yellow, blinking (strobing) or randomly works or not! , or at 70% brightness or below the tubes go Dead. (classic failure )
The yellow screen below is obviously bad , this is a very very common failure, the screen works ok but is jaundiced.
Run Windows Notepad (start button type notepad) if that shows yellow for white, the CCFL tubes are TOAST (no good) . Right click image 2 to zoom it.
mm lenght * diameter , 274= 10.8" inches
HP Made many CCLF Laptops, from year 1997 (first LCDs) LCD beat CRT's sales in 2010 Then the LED back lamped LCD screen was BORN !
The widest screens were upgraded first to LED then the cheaper tiny screens last.
Here is my list of HP devices using these silly tube things.(not full list)
CRT were introduced by IBM in 1981 (MDA, EGA, VGA , DVI followed, even HDMI now) all this is in the WIKI to read.
Some CCFL tubes are impossible to change inside glued LCD panel sandwich. (with out doing huge damage) There are exceptions to this rule. (and takes lots of skill)
Others you damage the LCD or it frame attempting the act, but some are easy to change. (why not look first and find the true there)
To change them tubes, it can be easy or near impossible , some are so deep in side that damage happens no matter your skills. see and easy one first here.
CCFL all fail ; most are now 2019 year.
Fixes are easy to impossible ( some screens are glued together or have clips that break and nows the LCD panel is useless after any attempted service repairs)
The easy ones are only those that are easy to reach, and them put them back new, and not wreck the LCD panel.
If you go to ebay.com you will see new LCD panels sold for your PC , for about $50 to $100 .
There are upgrades for only a few very popular PCs and monitors. (not the 10,000 models made since 1995)
They sell tubes here and upgade kits.
Here is fix, if you like to upgrade CCFL to LED, . (easy or hard or impossible are all possible here)
The plot can thicken easy, too easy if you have U tubes inside, good luck finding the correct size. ( 3 U-tubes might become 6 long straight tubes if you try.)
If it has U Tubes, shaped, we can (glue in 2 straight tubes wired in series can work, nothing to lose trying but cash) Finding those is near impossible. (YMMV)
No two monitors or Laptops are the same, each is custom design and complex disassembly.
Here is the repair flow logic, that can work for you: (given the flash light test proves the CCFL are no good.
The inverter is a high voltage DC to DC inverter, it is 12vdc input an 1000vdc out. So don't get shocked playing with it. This HV allows the CCFL to do instantant start up. (there are no heaters in the tubes, thus the word COLD)
The inverter is really a AC chopper. DC in is turned to AC then goes through a transformer, and is rectified (diodes ) High voltage for the silly HV tubes to work.
This chopper may have dimmer control (PWM methods), below is a universal inverter on the left and the CCLF tester on the right.
If you switch to a universal inverter the screen will be full brightness all the time with 12vdc on the input all the time.
This is how this CCLF technolgy works, and why it fails: (do not read this it makes your head heart)
The CCFL the cold cathode Florescent lamp tube. ( these can go dim in 2 years of continuous usage (no sleep/hibernate modes used) 20,000 hours is the typical life span (yes ,short)
Lamp life is defined as the brightness decreased to 50% of the original.
LED's can go for 20 + years full tilt. Most CCFL lamps seem here, ended in the year 2010. (this is all legacy junk now, best is to upgrade the PC or Monitor and retire this old junk, IMO)
Some tubes need 500v to 1000volts and 40kHz chopper square wave driver, and by level of dimmer setting.
The Phosphors inside age and go dim fast from these aging effects stated below: As they age and dim they love to turn YELLOW.
CCFL contains mercury gas, it is dangerous to inhale it. when the CCFL is broken! (the gas can be a mix of Ne-Ar , neon argon)
Due to degradation of phosphor from Hg consumption . (Hg = atomic symbol for Mercury gas, very TOXIC too, do not break them and sniff them, okay?)
Ion UV bombardment from the discharge column may be the attributing actor in depreciation of the Phosphor (age effects many)
Ion bombardment of the phosphor over a period of time can cause the inner layer surface of a phosphor coating to become non-luminescent (more aging effects)
Ion bombardment over time can cause some phosphors to have a greater tendency to absorb mercury. (as you can see, now, CCFL's SUCK for these reasons.)
99% of CCFL failures at about 5 years old is common, but we see 1% failures on inverters below.
20k hours is the life span, 10hr/ day , 2000 day life span, divided by 365 is 5.4 years. (the math is easy) Less if run every day at 100% brightness.
See inverter fails next, after some history below and HP secrets by model.
version 1. 12-9-2017