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Genesis problem with TV


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I usually have my model 1 genesis hooked up to my 40" Visio, just for convenience since it is my main TV. The problem is that the picture vibrates back and forth on the screen, which may or may not stop during the game. I brought the genesis over to my friend's house and we hooked it up to his even larger TV and it had no problems with picture,as at first I thought that it might be the fact that it was an HD TV (only thing I could think of). What could be the problem with my TV?

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From memory, the Genesis puts out a very non-standard NTSC signal, so that might be what's causing the issue. I'll defer to other folks who have more expertise on the matter, but I seem to recall something along those lines.

So it might be the fact that my TV may be pure NTSC and my friend's might have been and NTSC/PAL? I have heard in the past that many new TV's now are compatible with both signals.
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I think it's more that some TVs tolerate out-of-spec signals better than others. For example, my little brother's TV will roll and freak out on Atari 2600 games that play fine on my TV at home. The games that cause problems on his TV tend to have a higher scanline count, I think.


But other, more technically-expert posters like Chilly Willy would probably be able to answer this better than I can.

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Old consoles like the Genesis were made to run on old CRT TVs. Such systems used phase-locked oscillators driven from the sync signal to drive the yoke on the picture tube. Such circuits are relatively immune to variance from the "standard" for the signals. NTSC in particular has some really strict ratios to be considered broadcast quality; for example, the horizontal width of a line MUST be 227.5 cycles of the color burst clock. The Genesis instead uses 228 as it's easier to generate.


So the signal from the Genesis is CLOSE to NTSC (or PAL), but not quite right. On a 90's CRT, you won't ever notice. On a new CRT that uses digital processing, or LCDs that all use digital processing, it all comes down to if the processing circuit can handle those differences. Think about it a moment - like I said, the line is SUPPOSED to be 227.5 color burst cycles wide, but the Genesis is outputting 228 wide lines. If the digital circuit assumes the line will always be 227.5 cycles wide, every other line will be a full cycle off. Depending on how it handles the line input, it may lose the signal altogether once if gets more than a few cycles off.


If your TV doesn't handle the non-standard signal, there's little you can do. A TBC (Time Base Corrector) will regenerate the signal with proper timing, but those can be really expensive. Forums like SEGA-16 have tons of threads on LCDs that do or don't work with the Genesis. Your only other choice is to get a VGA converter box that supports the Genesis, then use the VGA input on your TV (assuming it has one). That would be cheaper than a TBC... probably easier to find for the average person, too. :)

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Honestly, it might be your TV. I've encountered this problem only on Visio tvs, and not just with the Sega Genesis. My former roommate had a Visio and we had the same problem. It also did a piss poor job with his PS2. I suspect that the Visio simply has a really crappy analog to digital transcoder built into it. Analog signals always looked awful on his TV.

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