From: legg@nospam.magma.ca   
      
   On Wed, 16 Nov 2022 17:25:07 -0800, RosemontCrest    
   wrote:   
      
   >I have a Seiki SC-40FK700N TV with what appears to me to be dim   
   >backlighting along the top 1/3 of the screen. The lower portion of the   
   >screen appears as normal, but about 2 weeks ago the top suddenly went   
   >dim; it's still readable, but dim.   
   >   
   >I don't know how many LED strips this TV has. I would appreciate any   
   >troubleshooting suggestions such as what nominal voltages I should see   
   >where. If it does turn out to be a bad LED strip, should they all be   
   >replaced while I'm in there?   
   >   
   >While I do have plenty of experience dismantling, repairing and   
   >assembling medical devices and computers, I have never worked on a LED   
   >TV. After watching some backlight repair videos, it looks rather   
   >straight forward.   
   >   
   >I think that I can find LED strips for ~$15/ea or so, so it may worth   
   >fixing this set. Thanks for any help.   
      
   Check the voltages on the connector to the backlight, and currents,   
   if possible. You should eliminate problems there, first.   
      
   You'll likely only be able to tell if the problem is with wiring   
   or lamps inside the backplane area after dismantling. You should   
   be prepared to replace the lamp strips at that time, because the   
   longer it's disassembled, and the more times you repeat that   
   operation, the more chance of damage in the process.   
      
   Most sets won't let you see a dead lamp strip - just shutting   
   down, which is most annoying. A lot of these things would be   
   capable of running with multiple single led failures in their   
   strips and no real difference in display quality . . .   
      
   . . . but the designer thinks differently.   
      
   A repair can often be made by simply jumpering the defective   
   led with a suitable voltage dropping resistor or zener, but   
   this is only something I'd do if replacement strips   
   weren't on-hand.   
      
   I had one set where a dead strip could be mimicked with a   
   10W power shunt on that line, without opening the thing up.   
   Dispay was acceptible to the customer, so it went back   
   with just that addition. Not a real fix and a symptom   
   that all the lamps needed replacement, but sometimes   
   quicker is better.   
      
   RL   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)