[SOLVED] Buzzing sound with Zenith screen

[DisizDream]

Hi everybody, I have a small problem and I hope you will help me.
I connected a genesis 3 to a Zenith LCD Screens.
I did the rgb mod to the genesis 3 with the resistance and capacitor and the picture is great !!
But I can't say the same about the sound.
The sound is buzzing all the time and it seems to buzzing more or less with the picture displayed.
Let me explain this : when there is a black screen (between the start screen and the game beginning for example) the sound is not buzzing at all, and depending of the scene of games (menu, intro etc) the sound is buzzing differently.
Has anybody already had this problem ?

Thanks

[Nintendott]

Do you use the sound from compasite?
If not, try that.

[DisizDream]

I just tried that but I have no sound at all. It seems that when you connect something in RGB, the screen is not using the composite audio in.
Other ideas ?

Thanks

[Nintendott]

have you connected the ground for the sound?
If the ground wire is thin, try replacing it with a thick one.

[DisizDream]

I have connected the ground of the genesis 3 to the ground of the lcd screen.
But yes it is a thin wire, I will try with a ticker one.
I think about something, during my tests, the genesis 3 and the screen each had their own power supply. Could this be the cause ? Maybe the problem will disappear when both will be connected to the same power supply ?

[Nintendott]

No, the backlight dissapears if the voltage/mAh is to low.
If the backlight turns on when you turn everyhting on, its not a power problem.
One more thing, if the speaker wires once fell off, you may have soldered them wrong like i did 2 days ago.
If the wires are soldered +- to -+, the buzzing sound will come.

[DisizDream]

So I tried a thicker wire for the ground but no changes.
I tried to connect only audio and removing R,G,B, Sync, +5v and Ground and the sound was perfect...
I reconnected only the R, G and B and once again it was buzzing...

Then I tried to remove a big capacitor that was soldered on the zenith screen board (it seems that official Psone lcd don't have this one) and the noise has reduced around 60% but not perfect yet...
I wonder what is the use of this capacitor ?

Now I see that with my zenith came a little board where the AC come in, pass trough 2x 1000uf capacitors, one resistance and then come out to the Zenith LCD. Should I get rid of that and connect AC directly to the screen ? I fear to do this because I suppose they are there for a reason ?

Thanks

[Nintendott]

Im sorry but i don`t know more about this problem

[DisizDream]

Ok i just found out the problem. I was using DB9 connectors to connect the genesis to the screen, and I had to solder a wire from the metallic part of the db9 connector to the ground and no buzzing sound at all. By the way I removed the small power board of the zenith, and the screen works fine, seem all these capacitors are useless ?!?
Thanks a lot for your help Nintendott.