Re: LG 42LN5400 - No Backlight
Thanks neilc6, I've got the backlight on 15%, is more than bright enough. Also changed on my other TV....
tekz
Member
Last Activity: 05-22-2020, 12:41 PM
Joined: 05-11-2020
Location: Folkestone
-
Re: LG 42LN5400 - No Backlight
Replaced the LED strip and TV is now working, thanks all, £12 fix
...Leave a comment:
-
Re: LG 42LN5400 - No Backlight
It's all still in parts on a table, as I understand it I can rip the LED off and solder the circuit closed? I do have a soldering iron but I've never used it before, purchased it to start to repair broken stuff but not got around to practising yet.Leave a comment:
-
Re: LG 42LN5400 - No Backlight
That's interesting because while I was testing the LED connector at the power board a few times the lights did flash when testing PIN 7 (could see it light up through the hole the cables go through and off again). I suspect this was due to the multimeter lowering the resisting briefly, just enough for the circuit protection to not kick in before the rest of the bulbs lit up for a second, perhaps because this bulb was at the end of the a row near the bottom of the stack. I couldn't reproduce it however but happened a few times incidentally.Leave a comment:
-
Re: LG 42LN5400 - No Backlight
That's a good point I had considered, I sourced one strip for £12, there were complete sets of 10 strips available on eBay for around £40. I'll just replace this strip, see if my repair is successful and consider replacing more or buying a new TV if more fail. I did just purchase a new TV 6 months ago so don't fancy buying a new one just yet but this has been a good learning experience so far which was the reason for half the effort (and to save money as the TV is mostly used as a YouTube player via Chromecast.
It's coming on Friday...Leave a comment:
-
Re: LG 42LN5400 - No Backlight
Hi all, I scraped and tested and I found one LED that refuses to light up, at the far end of one of the strips. Is it more practical to replace the whole strip as I don't have any equipment for changing LED's?
Any good sources for a LED strip quick delivery to UK?
Just to add a quick question for educational purposes, a stuck open LED means it failed in such a way that it opened up the circuit and now there's too much load on the rest of the LED strip circuit and the power supply is detecting excess voltage and turning off as a safety...Last edited by tekz; 05-11-2020, 03:23 PM.Leave a comment:
-
Re: LG 42LN5400 - No Backlight
Thanks neilC6, to confirm, I just scratch paint away either side of the LED's and test?Leave a comment:
-
Re: LG 42LN5400 - No Backlight
I think my multimeter diode mode is too lower wattage at 2.8V/1.5mA. Not sure where to go from here apart from ordering an LED tester. The LED's themselves don't seem to have anywhere to test individual LED's.
I have seen this on Amazon, would this work? [URL="https://www.amazon.co.uk/Digital-Computer-Backlight-Testing-Adaptive/dp/B07YY1MHD5/ref=sr_1_6?dchild=1&keywords=LED%2Btester&qid=1589225514&sr=8-6&th=1"]https://www.amazon.co.uk/Digital-Computer-Backlight-Testing-Adaptive/dp/B07YY1MHD5/ref=sr_1_6?dchild=1&keywords=LED%2Btester&qid=1589225514&sr=8-6&th=1[/URL]...Last edited by tekz; 05-11-2020, 01:53 PM.Leave a comment:
-
Re: LG 42LN5400 - No Backlight
I've got the TV apart and exposed LED strips, any guides on how to test with a multimeter in diode mode? LED strips look fine, no burn marks.Leave a comment:
-
Re: LG 42LN5400 - No Backlight
Thanks NeilC6, may end up trying that, it's an old TV so I want to try to pin down what's wrong before spending money on fixing.
Just measured voltages on the P201 port, below, do they look ok?:
STANDBY:
Top:
GND: 0
12V: 0
12V: 0
GND: 0
24V: 0
GND: 0
3.5V: 3.5V
3.5V: 3.5V
PWR-ON: 0
Below:
GND: 0
N.C. 0
12V: 0
GND: 0
24V: 0
GND: 0
N.C: 0
PDIM: 0
DRV-ON: 0
TURNED ON:
Top:
GND:...Leave a comment:
-
LG 42LN5400 - No Backlight
Hi there, the backlight on my TV has failed (LG 42LN5400). Sound works but no image unless I shine a torch. The LED's don't seem to flash when turning on.
On standby the power LED is red like normal, but when turning on it flashes 3 times.
This started while using my chromecast to play music, looked up and the image was gone.
LED voltages below power on (not sure if my meter is cheap but doesn't stay on a fixed voltage when taking these, fluctuates around by 10 or 15v constantly):
Pin 1:
Peak ~ 100
10 secs roughly ~100
... -
Re: New Members - please post your introductions here
Hi all, just introducing myself as suggested, guy who lives in Kent trying to fix my TV in lockdown).
/tekzLeave a comment:
No activity results to display
Leave a comment: