"Fixing" SNES for OSSC

[paulb_nl]

Also, if OSSC briefly loses sync, is there anything that prevents it from just going on a frame or two with a potentially jumbled picture (or, more likely, just a completely black one, in the case of forced blanking between scenes on certain consoles), rather than just immediately "giving" up, and telling the TV there's no signal now?

The OSSC doesn't lose sync with the sync jitter of the SNES. If the OSSC is losing sync (red led light comes on) then you have a different problem.

[Sumez]

I'm getting mixed signals here.

[Harrumph]

Yes because you have brought up different problems that have different answers.

[Sumez]

There's also the person saying "The OSSC doesn't lose sync" [due to the jitter] while another person says the image dropping out a few seconds is due to the TV taking time to resync when the OSSC loses sync.
The only way those aren't conflicting is if the jitter is not the issue, which conflicts with what was stated earlier on.

People definitely have different ideas of what it is that's happening here.

[paulb_nl]

It's simple. If you see "No sync" appear on the OSSC LCD or the green sync led changes to red then the OSSC has lost sync. If nothing changes on the OSSC then your TV is losing sync.

I see you said you also get this issue with your PAL consoles. I assume you mean the PAL consoles are modified to run at 60Hz?

[Harrumph]

Just to clarify further, if your OSSC loses sync, you have either a bad cable or some problem with the console itself (could be several things). If only the TV loses sync, then it’s likely jitter issue (but could be something else like general pixel clock tolerance of your display).

And about PAL, he’s asking because SNES in PAL mode doesn’t have the jitter (no short scanline every other frame). So that’s actually a way to test the issue. If the TV runs without issue in PAL mode, but desyncs in NTSC mode, then it’s pretty much certain it’s the jitter.

[Sumez]

That's a good point. I knew the jitter doesn't happen in 50hz, but didn't think to test that. I think it's pretty much been concluded this happens due to the jitter already though.

[DiegoPonga]

Also, if OSSC briefly loses sync, is there anything that prevents it from just going on a frame or two with a potentially jumbled picture (or, more likely, just a completely black one, in the case of forced blanking between scenes on certain consoles), rather than just immediately "giving" up, and telling the TV there's no signal now?

The OSSC doesn't lose sync with the sync jitter of the SNES. If the OSSC is losing sync (red led light comes on) then you have a different problem.

The problem is rather the screen, am I right?

[paulb_nl]

The problem is rather the screen, am I right?

Yes if the OSSC is not losing sync.

[rhpk76]

Thanks a lot to all for this very useful thread. I was really clueless about my European Supernintendo losing sync in some games, like the character selection in Street Fighter 2 Turbo.

Anyhow, I was able to solve the issue without messing up with the hardware (something I hate to do with items in my collection). I found that increasing the parameter "Analog Sync Vth" to 135 on the classic OSSC fixes the issue with a cheap LG 27UL500 Monitor 27" UltraHD 4K. I did not have the same luck with the previous monitor I was using, an HP PC V24i.

I post this for the records.