Dreamcast vga problem: horizontal lines moving all over the screen.

Since I bought this DC I never used it with a VGA box.
The console works fine with a RGB cable. The problem is that after some minutes I'm playing something on the screen begin to appear a lot of horizontal lines. If I give a small hit at the console the problem disappear but after some minutes it comes back.
Is this some overheating issue? With an RGB cable the problem doesn't exist.

 

Maybe the VGA box is faulty?


If the dreamcast overheats a black screen goes up and its like a fan not working you will know when if that ever happened touch wood it don't.

 

I suspect it may be your TV that's the culprit. You have to configure the setting on your TV for V and H.

Can you share which brand VGA adapter you are using (Retrobit, Blaze, Naki, etc)?

 

It's not the TV since I've tried 3 different tv/monitors. And is not the VGA box since I've told you that the problem disappear once I gently hit the console....
So I'm thinking that maybe is an overheating issue on some solder point of the AV output.
Anyway the vga box is a black one with EDGE written on it. I don't know if it's crap quality or what. If I try to move the cables or the vga box, or the cable behind the console, nothing change.
I have to "move" or hit the console to make the lines disappear xD
As I've already told you, the problem doesn't appear as soon as I turn on the dreamcast but after some minutes of playing.

 

Hmm... That's quite a dilema you got there. You wouldn't happen to have a spare DC console or perhaps get a friend who may have one to lend to you to test and remove all doubt?

 

That's the problem. I don't have it. Anyway I took some photos, well... 2 actually... (yes I'm playing Grandia 2 at the moment xD ).
http://imageshack.us/g/1/9858304/
Tonight I'll play with the RGB cable and I'll see what happen.

 

I've played for some hours with the RGB cable, no strange lines. After I've played the last session of Grandia 2 I've turned off the console switched to VGA turned it on and the lines were already there(even on the dreamcast boot screen). So it IS an (over)heating issue. I'll try to see if there is something wrong near the AV port.