LG Flatron starts w. coil whine and power issues

[Bitvive]

Hi ,

My old LG Flatron recently started with coil beeping. This got worse every day for a few days until it also started having power problems.

Now it also went off again after displaying the LG logo, then on, off again, then on and so on...

So far I have measured the power supply unit, which delivers 19.21V and should therefore be OK. I removed the circuit board and connected it to the mains plug so that I could hear the coil beeping.

During the beeping, I pressed on the coils with a non-conductive tool to see if the sound changed and to find the defective component. That's what I had read.

Now I probably only have the option of measuring with a multimeter? I still lack the experience and know how to find errors by measuring.

I don't quite know how to find the faulty component at the moment, can you help me?

PCB:
E42V
EAX64485303

Bear with me, I'm still learning... :p

[lotas]

The fact that the power supply produces 19v does not indicate that it is working, it must be checked under load, that is, connect it to the board and measure on the other side of the board at the connector contacts what voltage there will be (this will be under load) if the voltage is low and jump when you turn on the board, then split the power supply and change the electrolytes (capacitors).

[lotas]

The fact that the power supply produces 19v does not indicate that it is working, it must be checked under load, that is, connect it to the board and measure on the other side of the board at the connector contacts what voltage there will be (this will be under load) if the voltage is low and jump when you turn on the board, then split the power supply and change the electrolytes (capacitors).

[Bitvive]

The fact that the power supply produces 19v does not indicate that it is working, it must be checked under load, that is, connect it to the board and measure on the other side of the board at the connector contacts what voltage there will be (this will be under load) if the voltage is low and jump when you turn on the board, then split the power supply and change the electrolytes (capacitors).

Thanks for the hint mate.. I should have thought of that myself. It actually only measures 15.42V under load. With the laboratory power supply set to 19V 1.7A,
the display works and does not emit any coil beeping. It can be that simple, new power supply is ordered

[lotas]

Ok. Yes, you can repair the original power supply, carefully split the plastic case along the seam, get to the board and replace the capacitors...

[Bitvive]

Ok. Yes, you can repair the original power supply, carefully split the plastic case along the seam, get to the board and replace the capacitors...

You were right! The case was a real pain to get open, but I immediately noticed a 680 uF 25V electrolytic capacitor that was blown.
I replaced it and the monitor now runs with the repaired power supply unit without any coil beeping or errors. Great, thank you

[lotas]

Ok, congratulations, they have a disease with electrolytes, but they restored the original power supply and did not have to buy a fake power supply....

[Bitvive]

Ok, congratulations, they have a disease with electrolytes, but they restored the original power supply and did not have to buy a fake power supply....

Hi Lotas,

Now my screen simply switches off after a few hours of operation and can then be switched on again normally. What are you thinking? Replace the large 420V buffer capacitor as well?

[lotas]

Hi, it’s better to replace everything there if you don’t have an esr meter (they may look good, but their esr may increase and the capacity decrease) and set better quality ones to 105 * degrees, since the power supply heats up and there is no ventilation him.