Unstable Backlight on LG 39LB5610 TV: LEDs Not the Issue, Voltage Fluctuations Noted

The television has a strange condition. After about 30 minutes of work, the backlighting becomes unstable. It flickers, flashes, sometimes it turns off altogether. it happens a few-tens of seconds and the backlight is still working properly. The initial diagnosis - backlight wear - is rather wrong. Measurements of the strips showed 3 LEDs with a forward voltage of about 7V, the rest 6.6V at 300mA. 7V diodes were omitted for the test - but this did not solve the problem. No other signs of LED wear are visible - they all shine evenly, with no discoloration. Soldered connections, batten connections are additionally bridged.

This TV is used, the BD9486F is not available from us. During the flickering, the supply voltage to the LEDs changes 170-230V. I omitted the MOSFET on the ground side, leaving the LED current measurement - it did not change anything. Measuring resistors replaced. I have managed to measure that during the unstable behavior of the power supply, the voltage varies on PIN1 BD9486F marked with UVO5.0. It varies around 4.5-6V. It seems that the instability of this voltage results from the damage to the BD itself, but as I mentioned - the system is difficult to access, the power supply itself is not cheap either. After the laminate, I do not see any other connection to this pin that could affect the level of this voltage. Can someone confirm whether this system can be the cause of the failure? Or maybe actually LEDs and I am looking unnecessarily?

Motherboard LGP3942-14PL1

Ibuprom wrote:

the power supply itself is not cheap either

On ebay from nearby Czech Republic EUR 19 with shipping, use the number that starts with "EAX ...."

I found a CD for ~ 200 PLN with us. I just did not want to buy blind because there are no returns and the fault is unusual and ambiguous.

But I guess I'll answer myself. Connecting the capacitor 220u to pin 1 of the BD stabilizes its operation. The backlight has stopped flickering and the TV has been working for several hours without any problems. So in this case, I will have to buy the CD, and in the future I will have to order a few spare BDs from Asian friends.

e.g. Link_ LGP4750-13PL2 EAY62810801
IC801 BD9486f
IC101 SSC9527S
IC601 R2A20133D

Pin.1 BD9486f Link to nap. + 5V (out)> "made" from Backlight SW
ps
In Kiev, it costs about $ 6 / pcs * you have to wait sometimes (I don't know if they send to PL?)

For example, in LG 42LB620V (matrix LC420DUE (FG)) there are
- 4 strings (lines) 8 Led each, nap. power of the ruler is 49V
* i.e. Led 6V
On exit inv. (integrated into PSU> pcb: EAX65423701 (1.9)) is 196V (205) / 250 mA

It was this scheme that I used to diagnose this fault.

Additional question - for the future. I mentioned the diode conduction voltage. 3 pcs had 7V, the rest 6.6 - at 300mA. Do these 3 items end their lives or can it be blamed on the production spread? As I mentioned - they glow the same as the others and you can't see anything happening to them. Cold diodes have a slightly different operating voltage (for these 3 diodes - 7.5V, the remaining 7V), but after a few seconds their voltage stabilizes at the previously mentioned level.

Hello.
Leave the LEDs alone.
Greetings

Ok. Thank you for all your comments. greetings