From: ohg...@gmail.com   
      
   On Saturday, July 23, 2022 at 12:33:56 PM UTC-4, Peabody wrote:   
   > Well, I had a major setback trying to diagnose the repair. Last night I    
   > set it on the dining room table, face down, and this morning I did the    
   > flashlight and audio test again before even taking the back cover off,    
   > just to confirm the video and audio were still working. But after about 30    
   > minutes, the TV started working again. All the backlights came on, and the    
   > picture is perfect. This is the behavior the owner reported - it might    
   > get backlight at any time, or it might not.    
   >    
   > I measured 267V between BD9101 and J858, so that's the benchmark in case it    
   > dies again.    
      
      
   Keep a meter on it all the time.  If it has a min/max recording feature,   
   connect a DVD player and leave it on the title screen so the TV doesn't   
   dynamically adjust the back light to scene content or time out and shut off.    
   Check the max voltage every    
   once in a while.  If your baseline drifts more than a tenth or so with no   
   change of picture content, it indicates a failing LED (they do intermitt both   
   towards open and leaky) or a bad interconnect between the A/B sections of the   
   LED strips or where the    
   LED strips plug into the main feed strip.   
      
      
   > So I don't know how you diagnose anything when it's working properly.    
      
   Sometimes we take the display out and they come to life by themselves.  It   
   happens.  One thing to do is put a meter across every connection and see if   
   voltage appears across any connection (should be zero volts).  Any voltage   
   across an interconnect means    
   a bad connection. If there is any voltage drifting even with the LEDs   
   appearing to be running properly, we know we can find it.     
      
   Sometimes we have to hard wire all the interconnects - if just one is bad,   
   another will follow eventually.   It's not intuitive but poor connections   
   *don't* show much if any change in brightness even when tapped on as the LED   
   drive controller is    
   extremely fast and compensates immediately for any change in load impedance.    
   Only when the connection is bad enough to cause the controller IC to detect   
   either an overvoltage or undercurrent condition does the LED array shut down.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)