From: beeper@acme.com   
      
   On 11/18/2022 5:23 AM, legg wrote:   
   > 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   
      
   Thanks for the useful tips, legg. It may be a few more days until I look   
   into it.   
      
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