LG 47LM960V , No sound

[HristoM]

Hello!

The speakers produce no sound except for some very silent static. The tv has a subwoofer that works, but after a while just goes silent, restarting the tv turns the subwoofer back on. Ive changed 3 ICs (NTP-7500L) as well as measured output voltages(12v DC - half the supply voltage) , Power supply voltages(24v DC) the 3.3v normal is also there. Using an external amp i can hear the audio in(lots of static in it however). the only things left are the amp_reset and amp_master_clk which all come from the microcomp(R5F100GEAFB). The headphone jack also works. i hope someone has had a similar problem.

Im attaching the Service manual and a picture of the IC

Thanks in advance!

[lotas]

Re: LG 47LM960V , No sound

Check the mute signal, the transistor and capacitor are not shorted.

[nomoresonys]

Re: LG 47LM960V , No sound

Something that sometimes works, plug in and out the headphone jack several times, just something to try.

[HristoM]

Re: LG 47LM960V , No sound

Check the mute signal, the transistor and capacitor are not shorted.

Checked the input signals with an osciloscope- they look alright. sda and scl as well as the aud_master_clk seem unreadable. The transistor and capacitor are alright, checked the same cap on the subwoofer amp- all good. The 3.3v are coming to the fault pin , but what worries me is they are 3.2 not 3.3v. Usually this doesent matter but i read somewhere that its okay to be 3.4 not 3.2. Tried plugging and unplugging the aux- didnt help. Reset the audio master settings-still nothing. The IC gets hot, meaning it does work, so at this point im narrowing it down to the MICOM microprocessor having a communication problem with the amp.

[HristoM]

Re: LG 47LM960V , No sound

Hello!

The speakers produce no sound except for some very silent static. The tv has a subwoofer that works, but after a while just goes silent, restarting the tv turns the subwoofer back on. Ive changed 3 ICs (NTP-7500L) as well as measured output voltages(12v DC - half the supply voltage) , Power supply voltages(24v DC) the 3.3v normal is also there. Using an external amp i can hear the audio in(lots of static in it however). the only things left are the amp_reset and amp_master_clk which all come from the microcomp(R5F100GEAFB). The headphone jack also works. i hope someone has had a similar problem.

Im attaching the Service manual and a picture of the IC

Thanks in advance!

UPDATE: After tinkering around the transistor for amp_mute, the sound came back leading me to believe the problem might be a faulty transistor as disconnecting the collector of the transistor seems to have fixed the problem. Either that or a bad solder joint somewhere around it.

[lotas]

Re: LG 47LM960V , No sound

Most likely it's not soldering, but there may be a leak in the transistor junction.

[Davi.p]

Re: LG 47LM960V , No sound

That tv chassiss suffer from bad cpu solderings, if you buy a special long nose "clack" plier, sorry i know only italian name "pinza a scatto" you can test it carefully..

[SERKAN BİLEN]

https://youtu.be/Yy4-tYnP4i4?si=ST7dXp7aGGB-VOAi