From: legg@nospam.magma.ca   
      
   On Wed, 13 Jul 2022 11:14:21 -0700 (PDT), "ohg...@gmail.com"   
    wrote:   
      
   >On Wednesday, July 13, 2022 at 7:43:19 AM UTC-4, legg wrote:   
   >> Just finished relamping a very modest flat screen, only   
   >> to discover that the screen itself was damaged.   
   >>   
   >> Any way to see this without backlighting?   
   >>   
   >> RL   
   >   
   >Depends.  Some TVs with back lighting failures shut down, but others continue   
   to run.  If you have sound (check every input), the TV is not shutting down   
   and a *bright* flashlight shown on the screen at several angles may show a dim   
   picture.    If you    
   can get that far, look for a screen with no cracks and no lines or bands in   
   the image.  Look OK?, pull the screen.   
   >   
   >If the TV doesn't shut down and has more than one "channel" of LED lighting,   
   *disconnect* the LED harness and use an LED tester to light up any remaining   
   working part of the LED array.  With the LEDs partially running, turn on the   
   TV and observe the pic.   
     It will be dim and uneven, but you can access the overall condition of the   
   display.   
   >   
   >If it shuts down, go over the screen with that *bright* light and look for   
   cracks.  There are ways of fooling the TV into not shutting down with a back   
   light error but it's usually easier to just use a bright light.   
   >   
   >I've done several thousand at least back lighting repairs, and sometimes I   
   discover a crack only when the screen is removed.  I hold the screens up  to   
   my shop lights as if I was making an offering to the TV gods.  A crack will be   
   visible when holding    
   it up to a bright light from behind.   
      
   I normally disconnect the screen by lifting off the back assy -   
   just leaving the display layers flat. No thought of moving it   
   around, unsupported. That's asking for trouble.   
   >   
   >Sometimes, you can repair the back lighting and you might discover an   
   electrical failure of the display or a debonding of the ribbons either at the   
   address boards or at the glass itself once you put it back together. Nothing   
   you can do about that - it    
   happens.   
   >   
   >That all said, I can tell you that pulling screens on TVs is delicate and   
   most amateurs break nearly all the screens they attempt to fix (no offense).    
   Many screens are taped in the frame and must be heated carefully and a thin   
   membrane used to separate    
   the screen from the frame.  They crack so easily you won't even know it until    
   you put it together.  If the screen isn't sitting back down flush in the frame   
   when the mask is reinstalled you will crack the screen.  If the address boards   
   are not handled    
   like newborn chicks, you will damage one or more of the ribbon bonds to the   
   screen.   
      
   Having tested and found dead leds or led strips, it was   
   dissapointing to see obvious impact damage on the   
   semiconductor screen layer, after the backlight was repaired.   
      
   No outward sign of mech trauma.   
      
   Leds were only $7.50, but took a month to swim here.   
   I assume screen layer replacements don't make sense $-wise.   
      
   RL   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)