SFC losing sync occasionally on Sony PVM

Hi folks, long time no see. Hope you're all doing well.

So, like topic says, when I play games on Super Famicom on my PVM-2730QM via RGB SCART, occasionally (once every 5-20 minutes) it seems to lose sync, there's a very brief flicker and it goes black for roughly half a second or so, sometimes multiple times in a row varying in how long the black period extends. Pretty irritating, as you can imagine!

I've got a couple of SFCs, both exhibit the same behaviour. It affects all games. (I also have a flash cart and a Super Gameboy and get the same problems there, for what it's worth.)

Other consoles do not cause this issue.

I can't remember the name/manufacturer of the SCART cable (bought it a decade+ ago!) but it's fairly chunky with a ferrite bead. Not super cheap garbage, anyway. I don't have a second to compare against.

Would a csync SCART cable resolve this? Or any mod?

 

I had a similar issue with a NTSC N64. From time to time when the image on the screen was darker I was losing sync.
In my case I used a RGB cable that had a 75R resistor from scart pin 20 to GND. But according to schematics found online for a NTSC console the resistor should not be present. After removing the resistor the problem was gone.

So my advice would be to check the RGB cable against this schematic and see if there is anything different:



You can use a multimeter to messure the resistance between the GND pin and pin 20 to see if maybe you got the exact same issue.
You can also count the capacitors, there should be 3 and not 4 and also not 0.

 

Damn, that sounded hopeful. Just checked and there are only three caps (and a couple of resistors on the audio lines). I never get any screen darkening, incidentally - the image quality is fine other than the occasional flickering to black.

Thanks for the response, though.

 

Its possible the resistor is in the console end. Best to check with a multimeter as its a pain to open that end on a lot of cables.

 

Good call, but composite measured the same as the rest (when measured above the caps/resistors, obviously).

I misread sanni's post. The flickering occurs randomly, as best I can tell, whether the screen is bright or dark. It also happens when there are lots of motion and colour changes, and when there's a mostly static image (thinking Mario Picross, or Tetris on Super GB). If that's not conclusive I could use the 240p test suite ROM to check against a variety of images, but it would take quite a while... is this worth the time?