MrAdam83
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Oct 22, 2018, 1:20 AM
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Sharp LC-55N6000U has Standby Light but won't power on
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This is my first adventure repairing a TV but not general electronics, I have an IT background and work for a Automation Controls company; There is a lot I don't know but I am comfortable with most repairs and troubleshooting.
We bought this TV less than a year ago from walmart but it was the display model, got a decent discount and expected to get at least 2 years out of it.
Watched TV yesterday morning, shut it off, and went to the Pumpkin patch; Came home that afternoon and the TV would not power on.
The standby light was on solid but the TV would not power on from the power button.
Tried pulling power and waiting but must not have let it sit long enough, it would still not power on. Found some vague information about holding the input and Vol- while plugging in the power cord. Tried this reset method and was then able to power the TV on. Slightly moving the TV on the mount caused it to reset though, the standby light would come on and stay solid. Tried a few more times and found if I lightly tapped the upper section of the back panel it would reset, the standby light always came on solid.
Pulled the TV down and removed the back cover, Found the red\black power leads (grouped with a Blue\white pair) were nearly cut in half due to improper routing, pinched between the back cover and the wire keeper they were supposed to pass through.
Also found 2 grounded mounting screws for the PSU were missing (PSU is a RSAG7.820.6106/ROH). I repaired the wires with solder and heat shrink, then replaced the missing screws with a set from my junk bin.
Re-assembled and the TV, reinstalled it, and plugged it in; the standby light came on solid and the TV came right on when I tried it. It worked fine for about 10 minutes and powered back off suddenly; the standby light came on and stayed solid, that is where I am now.
The PC tech in me thinks its the PSU, maybe overheating and doing a thermal shutdown. What I read related to other models with Standby lights suggest that if the standby light is on solid as normal then the problem is not the PSU.
What do I need to check?
What voltage should I see on what pins from the PSU to the Main board? I don't see any 5v and have one pin reading 20v.
I can provide images if this Forum Supports them.
Edit 1 - reboots and powers back on if I lightly tap the processor on the main board.
Edit 2 - pulled main board, pulled heatsink from Proc, all looked good, re assembled WITHOUT new thermal paste, and reinstalled. now I CANNOT replicate the reboot condition.......
and now it seems fine.........
ideas welcomed.
(This post was edited by MrAdam83 on Oct 22, 2018, 2:07 AM)
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