Screen Audio Issues

[ByteMe]

Hey guys. I recently received my 5.6' display that I got for use in my soon to come portable, but am having some issues with the built in mono amp it came with, and could use some more experienced modders advice. The screen works great, but when I connect headphones or speakers to the proper jack on the control board, all I get is really loud distorted sound. Sadly the seller did not include the technical specifications, and I am unable to find any online. I am feeding the screen with the recommended 12v and the signal is coming from a unmodified gamecube console. Any help or insight you guys could provide would be greatly appreciated. Need to know if it is feasible to use the built in amp, or if I will need to bypass it.

I have included some close up pics of the driver board, as well as the current setup I am using. I can provide additional pictures or videos if necessary.

 

[Pinotte]

do you have volume control? If so is the sound distorted at a lower volume?

 

[ByteMe]

Yes, sorry for not clarifying, the volume control is on the control board, and is controlled digitally via a tact switch and is displayed on the screen. This problem I am experiencing is at the lowest volume setting, level 1 of 63, the problem just intensifies as volume is raised, as should be expected.

 

[ShockSlayer]

Try adding some resistors on your audio input lines. I've had to do that in the past in order to limit the signal. Don't remember what values I used, but you can't hurt anything no matter how low or high you go.

 

[ByteMe]

I will do some testing and report back, I had tried doing something similar except on the output lines, hadn't thought of doing so on the input.

 

[ByteMe]

Well I tried a few different values, from my quite limited selection and found that 100k ohm seemed to do the trick. the only issue I am having now is that I am receiving a fair bit of interference, shortening the lines should correct this issue right? I also believe some of the interference is coming from the regulator for the backlight? (copper coils near edge of board) Would running some thicker ground lines from the controller pcb to the driver board fix this? Or would getting rid of the ribbon cable and wiring the whole board with thicker wire/shielded for the audio lines be a better alternative

 

[ShockSlayer]

Yeah that sounds about right. Glad to hear it's helped.

More grounds can't hurt. Shielded wire also works wonders against interference; in particular the kind found in official Nintendo AV cables is always the good stuff. Make sure to connect ground on both ends of it too.

 

[ByteMe]

There was one other thing I was wondering. Is there a way to bypass the power tact on the controller board. Basically I want the screen to turn on when power is applied to it.

 

[ShockSlayer]

You could try just bridging the pins on the button. No guarantees though. Might have to work some transistor magic if that doesn't work.

 

[ByteMe]

Have some time off so back working on this project. I am planning to led mod this screen and am wondering if I could get some assistance. I am wanting to know whats the lowest voltage I could use (since I believe 12 is only required for the inverter), and if the prior is possible where I would alternatively solder power/ground. I can provide any additional details if needed! Have searched for hours but cannot find a schematic for this model.

 

[cheese]

Based on the fact that I see some 78M0x chips (linear regulators), I can guess the power is sent through a initial regulator and then dropped again at the other regulators. The first regulator appears to be the one marked 81204, as the input of the other two regulators are connected to this chip. It may also be a good idea to replace the inverter and backlight tube with some leds, as they are more power efficient than the inverter/lamp combo.

 

[ByteMe]

Thanks! I messed around with my multimeter and found that: 12v goes to the inverter, and then is stepped down to 8v and 5v (i believe for the onboard audio amp?), so should be able to power with 7.4 I'm hoping. Anyway I tried replacing the backlight tube with two types of led's: 3mm flat head, and 3mm x 5mm staw head led's (4 of each). Both of them resulted in a severely uneven/dim lighting. Anyone have any suggestions who have performed the mod.

 

[ByteMe]

Or would it be wise to just order a new screen, any good sources? The only reason I was hoping to use this one was due to it's hard to find size (5.6" in 4:3), plus I enjoy the added challenge.

 

[Noah]

http://www.good-display.com/products_detail/productId=128.html