Hisense F42K20E static out of speakers even with sound turned down

[jmandawg]

Hi all,

I found a Hisense F42K20E in the trash. The picture works great, but there's static coming out of both speakers even with sound turned down to zero.

I'm attaching some pics. I'm not sure what happend to the main power board, it looks like crap.

[petehall347]

Re: Hisense F42K20E static out of speakers even with sound turned down

can you post a recording of the noise ?

[jmandawg]

Re: Hisense F42K20E static out of speakers even with sound turned down

Here you go, i had to zip it to be able to attach it.

[jmandawg]

Re: Hisense F42K20E static out of speakers even with sound turned down

Quick update, I just tested hooking a different speaker up to the output wire and i get the same static. The static also comes through the aux jack on the back of the TV.

[budwich]

Re: Hisense F42K20E static out of speakers even with sound turned down

what input are you using and what are you inputting? what aux jack are you referring to, the manual doesn't refer to one? You could try a factory reset to see if any thing changes. Plug in a headset and what happens to the speakers / what happens in the headset?

what is the auto volume control set to?

[jmandawg]

Re: Hisense F42K20E static out of speakers even with sound turned down

I'm using no input at all, absolutely nothing is plugged into the TV, it's just the blue screen, and that static sound is blasting out the speakers.

I tried an hdmi souce, and it works, and i get the hdmi audio, but i also get the static.

Sorry I meant headphone jack. If i plug headphones into the headphone jack, the speakers turn off as expected (no static out of external speakers) but the static comes through the headphones.

I tried a factory reset, no difference.

[budwich]

Re: Hisense F42K20E static out of speakers even with sound turned down

Ok... thanks for the clarification. sounds like you lost a capacitor on the audio circuit.

[jmandawg]

Re: Hisense F42K20E static out of speakers even with sound turned down

would that be on the main board or the power board?

[budwich]

Re: Hisense F42K20E static out of speakers even with sound turned down

probably the main board since sound is made there... how ever it could be "dirty power" coming from the power but I doubt that because then you would like have other issues. If you post good medium close of the main board in and around where the speaker outputs are on the main (going to the internal speakers), someone may recognize some of the chips involved which may get you some "hints".

[budm]

Re: Hisense F42K20E static out of speakers even with sound turned down

https://www.badcaps.net/forum/attach...4&d=1597787583

The Class D amplifier chip is in the bottom left of the board where the speakers connector is, you see 4 black round inductors to the left of the IC, and two Lytics caps to the right of the IC.
Does this TV have headphone output and if it does, do you get noise on the Headphone jack also?

[petehall347]

Re: Hisense F42K20E static out of speakers even with sound turned down

not familiar with that noise ... do you get normal audio over the top of it ?

[jmandawg]

Re: Hisense F42K20E static out of speakers even with sound turned down

https://www.badcaps.net/forum/attach...4&d=1597787583

The Class D amplifier chip is in the bottom left of the board where the speakers connector is, you see 4 black round inductors to the left of the IC, and two Lytics caps to the right of the IC.
Does this TV have headphone output and if it does, do you get noise on the Headphone jack also?

Yes it has a headphone jack on the bottom of the right side and yes it produces the same static. Here are some closer pics.

[jmandawg]

Re: Hisense F42K20E static out of speakers even with sound turned down

not familiar with that noise ... do you get normal audio over the top of it ?

Yes I also get normal audio out along with the static. The static is very loud so even at high volume you can still hear it

[CapLeaker]

Re: Hisense F42K20E static out of speakers even with sound turned down

check all the other inputs and the tuner for the static noise. Maybe to a factory reset too.

[jmandawg]

Re: Hisense F42K20E static out of speakers even with sound turned down

check all the other inputs and the tuner for the static noise. Maybe to a factory reset too.

Yeah it's the same sound on all the inputs, in fact the sound does not stop even when switching input, it is constant. Also tried a factory reset and it didn't fix it.

[budm]

Re: Hisense F42K20E static out of speakers even with sound turned down

Since the speakers has their own amplifiers to drive the speakers, the headphone also has its own amplifiers circuit, and both of them and both channels are making the same noise so it has to be something common to both of them.

Does the this TV have audio line outs through RCA jacks, try and see if the noise is there also.
How about when you set it to MUTE, does the noise go away?

[petehall347]

Re: Hisense F42K20E static out of speakers even with sound turned down

does the audio ic chip get hot ?

on another note try disconnecting speakers and try headphones again .

i am however thinking it could be a power supply issue .

[Diah]

Re: Hisense F42K20E static out of speakers even with sound turned down

this noise are static . it may caused by the dust (dirt you have on all boards) .first you need to clean all boards up and down sides. panel tabs ..sockets... with high pressure air

[CapLeaker]

Re: Hisense F42K20E static out of speakers even with sound turned down

I there a input switching IC, or do all the inputs go to the main IC? IS the main IC something like MSD blah blah...

[petehall347]

Re: Hisense F42K20E static out of speakers even with sound turned down

i noticed the noise has breaks like something is charging up then discharging then repeating etc etc .. could well well be corrosion or dust . as said above give it a good cleaning ..simple free things first . . i might scope the power supply or sub in a known clean supply for the audio .