32X Scrolling bars issue

Hi all. I'm having a problem with my 32X with 2 horizontal bars that scrolling vertically upwards during gameplay. Below is a youtube link to a video so you can see what it looks like. (view the video full screen, otherwise it looks wrong with wavy lines.)



SOLVED: The problem turned out to be the AC adapter for the 32X. The issue was harder to detect because I had two defective AC adapters.

More details:
>Using the 32X with a model 1 Genesis.
>There is a moderate humming sound that accompanies the scrolling bars.
>I just replaced all capacitors on the 32X but observed no improvement with the scrolling bars.
>The 32X is s-video modded. (http://retrotimegames.com/page12.html)
>The 32X, s-video mod and all, works perfectly as a pass-through for Sega Genesis games. No bars, no humming sound.
>I've tested the 32X with a different Sega Genesis, an unmodified model 2, and it has the same issue.
>The issue *may* be related to me using an overclock halt-switch on the Sega Genesis when a 32X game was being played, as the issue first appeared around that time and worsened after that. The system was not overclocked when playing a 32X game, however.

Thanks for any and all help!

 

It could be ralated to the luma line on svideo.

 

I don't think it is. If it were, why would it only affect 32X games and not Genesis games?

 

do you have the RF shields clipped in between the model 1 and the 32x

 

I don't have the RF shields that go between the 32X and Genesis, no. But I never had them and the 32X worked fine for months before the issue showed up. Also, I've read/seen videos that say the RF shields for the Genesis cart slot are unnecessary.

 

That looks like a typical 60Hz bar/ground loop. Check all your grounds inside and out.

 

My research initially led me in that direction as well. I'll look into it some more. Any tips on how to avoid a ground loop in general?

 

I once had a ground loop problem around 1998 (wow... it has been awhile). I had a TV, DVD Player, stereo receiver, and coaxial cable from external wall connecting through a set top convertor box - a device that also used power. I can't remember exactly how I solved it (sorry - it was 20 years ago). I want to say that issue was due to the coaxial cable/Tuner part of the circuit. And I may have added extra components to the circuit to reduce it or remove it.

On the other hand, it is also possible I was using mains plugs on both sides of the room for the equipment due to how everything was wired, and that caused a problem.

I would try to baseline it - Make sure you have everything (TV, Sega Genesis + 32X) plugged into the same outlet. Hook up video only for now using your modded output - don't connect audio, and try a 32x game. If it looks like external possibilities have been eliminated in terms of wiring, you probably want to look internally.

Did you ground both luma and chroma lines as well as the shell for your jack inside the 32X?

What happens if you put in a 32x game (Virtua Racing) and don't use the passthrough cable from the Genesis? Does the 32x output its part of the video signal with the same problem?

It would seem these two items perhaps eliminate your overclock halt suspicion since it also happens with an unmodified Model 2?

 

Thanks for the detailed reply. I'll hit this troubleshooting on the ground loop possibility hard tomorrow. I did ground everything in the s-video mod but I grounded it to the RF shielding and I think it's worth trying to ground it somewhere else on the board.

The reason I mentioned the halt-switch was because I was concerned that perhaps using the halt switch on the Genesis while the 32X was running a game may have damaged the 32X system. I have no idea if that is a reasonable possibility, however. Just a suspicion.

 

EDIT: the contents of this reply weren't helpful for anyone else troubleshooting this issue.

 

I wouldn't ground them to the shield. I would find a close ground point on the board and use that. Good luck with your endeavor!

 

OK so, after more troubleshooting than I'd like to admit, it turns out it was the 32X's AC adapter after all! The real problem was that I had TWO defective Genesis 2 AC adapters. Oddly, the AC adapters work fine to power a Genesis 2. However, when connected to the 32X, scrolling bars. A third, fully functioning AC adapter did the trick.

Thanks for the help!

 

Glad you found the problem, phillip. Do you still have those AC adapters?

There is typically a large uf filter cap used for line noise at some point (in the AC adapter or in the system) in the case of many consoles. I wonder if the AC adapters you have might have a filter cap that doesn't really filter all that well anymore. I don't think I have been inside one, myself.