no sound through speakers

[staticfree]

LCD42911FHD3D

Hi,

My tv stopped sending sound through the speakers. The headphone socket works so I know sound is getting out. . It stopped after I took out the kids wii from the composite on the side.

I replaced the main board but still the same issue. .
I don't have anyway to test the speakers. . Could it be the inverter board or something?

Any ideas welcome.

 

[Sam Gangee]

Are the composite video sockets on the mother board or on a separate board? It seems to me that the mechanical movement has damaged something in that area so that the stereo amplifier is no longer working.

I always use an old PP3 9v battery to check speakers. Crude but good enough, and provides insufficient current to damage them.

 

[staticfree]

All the input sockets (composite, hdmi, usb...etc) are on the main board. The headphone socket works fine which is on the main board also. So looks like I may need new amplifier board.

Edit: closer inspection shows a psu board and inverter board. Would the amplifier be part of the power supply board?

 

[Sam Gangee]

See where the loudspeaker wires go.

 

[staticfree]

See where the loudspeaker wires go.[/quote
]

To the main board. ..I've already replaced. Still same issue. So I'd guess the power board has the amp?

 

[Sam Gangee]

I don't follow your logic. The loudspeakers would normally be connected directly to the amplifier outputs.

If it were mine, I'd inject a signal at the volume control (or somewhere obviously in the audio circuit) and trace it through using an oscilloscope or simple audio amplifier. In fact, since you say that you have audio at the headphone output, I'd trace it from there.

 

[staticfree]

The speaker wires go to the main board. (All input/output connections such as speakers, ir sensor and hdmi) I tested the sub out connection (rca or composite?) And that works... The main board I replaced. But the same issue still stands. .. no sound via built in speakers. I tested the speakers and they do work. I don't have access to oscillator or any other tools.

So deducting the fact I've replaced the main board, I'm guessing that the amp is on the same board as the power supply. .. I've noticed the tv hums from the power supply. . Could a capacitor or something be dying?

 

[Sam Gangee]

Whatever the faulty "or something" is, it's affecting both left and right channels. However, without test equipment, and knowledge to use it, all you can do is use your eyes and fingers. I have occasionally found a fault in this way but I wouldn't rate your chances very high.
http://www.The-Cool-Book-shop.co.uk/electronics.htm

 

[NotAgainFFS]

My TV set has a software menu that switches off the internal speakers and yet allows the headphones to still work.

I'm sure you've already checked something like this out but I was scratching my head for an hour one day trying to figure out what has broken.