Sharp LCD Integrated Amp Mod issue

[pentium]

From the other thread I own an older Sharp Aquos LCD TV that's missing the control box. I instead used it as a 720p DVI monitor for a media center system in my room and thought I would also try to hack an audio in port to it so I could use the internal amp and speakers.


With the control unit missing the amp output is fixed so it's perfect for me to control the volume from the PC and not from the TV. I rerouted the audio in from CONNECTOR 2 to the external speaker out jacks. The modifications are seen below.





It worked with one glitch. If you had turned the TV on and off a few times you would not get audio out of the speakers. The only way to fix it was to unplug the TV for about 30 seconds.
Then two days ago my inverter had a fit again and when it was rapidly turning the set on and off I lost the audio. If I crank the volume all the way up on the computer I can faintly hear it through the speakers. During troubleshooting I found that if I funneled the audio in directly to pin 10 or 13 on IC3803 I would get audio back. Same applied if I went directly to 10 or 11 on IC3812, however with severe clipping.
The catch was that it would do so in mono only and if one of the internal speakers were unplugged both speakers would go totally silent.
I'm not sure what exactly shorted out here but it would be cool to get it fixed instead of replacing it all with some small amp.

[pentium]

Re: Sharp LCD Integrated Amp Mod issue

No ideas?

[ben7]

Re: Sharp LCD Integrated Amp Mod issue

No ideas?

Im confused as to where both the internal speakers are connected.

And, are you sure that you cut the right wires?

BTW, are the audio system control inputs (eg mute) connected to anything? If they are floating, that might explain the odd behavior.

[pentium]

Re: Sharp LCD Integrated Amp Mod issue

They all receive control such as muting from the external box which isn't present. It appears that without the box things like volume and muting on the TV side are effectively locked out because there's nothing to tell the audio board what to do besides amplify the input signal.
I believe my modifications are correct. They are at the least positioned correctly on the schematics. The only thing that did however confuse me a little was if there was a relation between ground and the SPK- lines. In someplaces they show 0 ohm to ground and in other places they are infinite.
Audio amps were never really my thing.

[ben7]

Re: Sharp LCD Integrated Amp Mod issue

They all receive control such as muting from the external box which isn't present. It appears that without the box things like volume and muting on the TV side are effectively locked out because there's nothing to tell the audio board what to do besides amplify the input signal.
I believe my modifications are correct. They are at the least positioned correctly on the schematics. The only thing that did however confuse me a little was if there was a relation between ground and the SPK- lines. In someplaces they show 0 ohm to ground and in other places they are infinite.
Audio amps were never really my thing.

Try connecting your inputs to the L in and R in of the amp part of the circuit (2/2, your third image)

That way the sound won't go through the audio processor circuits.

[momaka]

Re: Sharp LCD Integrated Amp Mod issue

Don't ground L-OUT- and R-OUT-! (at least that's what you're showing in your 3rd picture) With the speakers removed, you should get no continuity between L-OUT- and ground and R-OUT- and ground - if you do, that's bad. The main AMP IC schematic can be found here:
https://cdn.badcaps-static.com/pdfs/...d4899c0579.pdf

Particularly, have a look at the sample circuit on page 5 and compare to yours. Should be very similar.

[joshnz]

Re: Sharp LCD Integrated Amp Mod issue

Don't ground L-OUT- and R-OUT-! (at least that's what you're showing in your 3rd picture) With the speakers removed, you should get no continuity between L-OUT- and ground and R-OUT- and ground - if you do, that's bad. The main AMP IC schematic can be found here:
https://cdn.badcaps-static.com/pdfs/...d4899c0579.pdf

Particularly, have a look at the sample circuit on page 5 and compare to yours. Should be very similar.

I Agree I was going say that yesterday but didn't get round to it.

[joshnz]

Re: Sharp LCD Integrated Amp Mod issue

Hi I have made corrections to schem2
The inputs have been marked with left in and right in
connect the signal to the points marked
and connect the speaker terminals as marked.

[budm]

Re: Sharp LCD Integrated Amp Mod issue

So did you lift the left side of the resistors R3942, and R3943 and feed the line level audio to those two resistors?

[joshnz]

Re: Sharp LCD Integrated Amp Mod issue

So did you lift the left side of the resistors R3942, and R3943 and feed the line level audio to those two resistors?

Not my project it's Pentium's
Pentium had connected the inputs much earlier in the system,
I have marked where I think will be a good place to insert the signal at (R3942 and R3943) just after the muting circuit.

And for the outputs I have marked where I think is the best place to take the audio from to drive the speakers, and that is ferrite beads (fb3807 and fb3808) and (fb3809 fb3810)
before the relay RY3801 that sets the output to the internal speakers or the external speakers.

[pentium]

Re: Sharp LCD Integrated Amp Mod issue

Ah, so I CAN tack in later on. The SRS circuitry was really confusing me. I'll give it a try tomorrow.

[pentium]

Re: Sharp LCD Integrated Amp Mod issue

*pop*
*fizz*

Oops. Looks like I'm going to have to shim in another amplifier instead.

[ben7]

Re: Sharp LCD Integrated Amp Mod issue

*pop*
*fizz*

Oops. Looks like I'm going to have to shim in another amplifier instead.

...........

lol

[joshnz]

Re: Sharp LCD Integrated Amp Mod issue

*pop*
*fizz*

Oops. Looks like I'm going to have to shim in another amplifier instead.

What did u do?

[ben7]

Re: Sharp LCD Integrated Amp Mod issue

What did u do?

Probably connected a bunch of wires randomly to the board!

lol, just kidding, but yeah, its annoying when you fry something xD