S Video is flashing on my CRT

[jadelocked]

Hi I'm searching the Internet for support but I thought I would ask here,
I was using VGA cables with a flatscreen TV, and I recently switched the Dreamcast to a CRT that has S Video ports. Whenever I start a game, the screen scrolls vertically repeatedly for several minutes until it slows to a horizontal solid black bar in the middle of the screen that separates the bottom and top of the image, so the bottom of the image is on the top half of the screen and the top of the image is on the bottom half of the screen. Then the bar settles at the bottom of the screen and cuts off the bottom of the screen, after a few more minutes the CRT flickers and then it's fine and everything looks ok until the next time I turn it on.

First I would like to know is this bad for my CRT? Is my CRT doing something to correct the signal from the Dreamcast, because it can't handle what the signal is sending? So far it has always fixed itself but I have to wait about 10 minutes every time.

My CRT may be having trouble finding the screen position whenever it changes like when I start a game and there are FMV cutscenes that move up and down as scene transitions. Certain games seem to help the CRT find the screen position faster like Rush 2049 has less flickering although it still takes just as long for the problem to go away. The car being in the center with the road moving up and down seems to help stop the screen from jumping as much, but it's still too much to be playable for 10 minutes. If I load King of Fighters, the screen just scrolls vertically too fast to do anything and I would say it's a seizure warning.

The Dreamcast menu has no issue if I don't put in a game. I can change VMU memory settings with no problems. Also, even when there is a game it will be fine until the game starts. The white screen for Dreamcast startup displays correctly, and the white Sega screen when the game is starting also displays correctly. It's only when the screen goes black and comes back it flickers for several minutes.

I was thinking maybe because the hacks I'm playing all have "force VGA" enabled, but that doesn't explain King of Fighters which is not compatible with VGA when forced, and has the same problem. I mostly just want to know if this is a bad sign for my TV because I don't want to mess up my TV.
I also switched my Gamecube to S Video just to see if it had the same problem to know if there is a fault with my CRT, and the Gamecube has worse problems with text lines blurring over to the right and a bunch of small horizontal white and black lines always coming and going in the background. They don't affect the TV menu if I access the menu, so it seems like the TV is ok just not with the S Video signal. With the Gamecube, the problem with the white and black lines never goes away. I will try using a real disc but I don't think the disc images I'm using from a SD card would automatically have an incompatible video signal.

[Ian Micheal]

Not sure whats going on there you sure this not because the game is thinking it's pal ? sounds like it with the vblank rolling .. Not knowing where you are.. could just have a bad crt when it's in s video mode.. 480i is very flickery anyways.. VGA only for me..

[jadelocked]

Thanks for replying Ian

Everything is US-NTSC the consoles and games I'm having problems with. I was thinking somehow maybe PAL 50hz mode is being triggered but that doesn't make sense especially with my most recent trial:

I just tried my Gamecube with a real disc and it's the same problem as the Dreamcast both using official S Video cables Sega and Nintendo. There is a horizontal solid black bar in the middle of the game menus that puts the bottom of the image to the top of the screen and the top of the image to the bottom of the screen, and Super Monkey Ball is a good game to see what's going on because in that game you only move the screen itself with the joystick. If I start an arcade mode level, then roll backward the TV seems to figure out where the top and bottom are for the screen, except the bottom of the screen is cut off by the solid black bar. Whenever I start moving forward the screen jumps up and down really jittery so it's unplayable. If I pause the game, the screen is showing as cut in half again with the horizontal solid bar in the middle. When I resume the game it's back to cutting off the bottom of the screen, and I also noticed the right side of the screen has a very thin vertical black bar that goes almost to the top with the uppermost scanlines being the only ones to reach the full horizontal length of the screen. If I access the TV menu the menu displays fine with the display problems showing up in the background. Also, the "Video 3" input text never goes away at the top of the screen.

I didn't notice the thin black and white lines with the real disc, it may have been just one game with that problem, so putting a real disc in the Gamecube for now makes it the same exact problem as my Dreamcast!

[jadelocked]

well I guess if I'm having the same problem with 2 different devices, it must be the TV...

i was confused because it seemed like the Gamecube was having a more serious issues, but I replicated the same problem as the Dreamcast so it must be the TV.

So does anyone think this is bad for the TV if I keep using it anyway? That's my main concern for now. maybe there is a problem with the TV S Video processing, but for now it works if I leave it on for 10 minutes, but I'm worried about making my TV worse with it flashing and scrolling vertically and jittery lines for 10 minutes every time I turn it on.

I'm worried about the time to correct itself taking longer every time until it can't work no matter how long it stays on. Would it be cheaper to get it repaired before it gets worse, or would it be the same repair either way if it does finally stop working?

I also think maybe it's not a serious issue and nothing else is wrong with the CRT so I could maybe reset the S Video ports. I used them for composite cables in the past so the TV may not be set up for S Video correctly? Does that sound more reasonable than TV broken on S Video ports but working fine with composite plugged into those ports?