Hi, I have performed the 50/60 Hz Mod on my PAL SMS2. At first everything seemed to work correctly, and I could switch between the two modes. So I set it 60 Hz and started playing. After a couple of minutes the graphics started to corrupt and after a couple more minutes the game hung. So I powercycled the console only to see that it would no longer boot, the screen would remain black. I inspected the mod and found out that the console would now only boot if I leave IC5 pin 57 floating, that is unconnected. If I connect it to +5V (meaning 50 Hz, as the console originally was) the screen just stays black. If I connect it to GND the same happens, but I also get a weird buzzing noise from the speakers. Even when floating, the image is not stable at all, it seems the console is constantly switching between 50 and 60 Hz, so the screen keeps moving up and down. I tried following the Service manuals and inspected the clock lines. Unfortunately I don't have an oscilloscope, but I do have a logic analyzer. I'm not sure what I got is meaningful, but it shows that the clock is irregular: Any hints of what could be wrong?
'llo here I'm very happy you're still working on this mod. Congratulation for your perseverance ! Unfortunatly, i can't help you for your issue, but i'll follow your work Tomorrow i'll be back to work, so i'll be here daily as usual. See ya !
Yeah, as you know this is part of a bigger project. Actually this was supposed to be the easy part, as there's plenty of docs around, and a lot of people seem to have done it. Still, it killed my SMS .
What is your sample rate set at? Saleae's Logic output will look like that if it is sampling at a slower speed than the line in question is oscillating.
Sample rate was the maximum possible, 24 MHz. This should be enough to sample all the signals according to the sampling theorem, since the one with maximum frequency is slightly more than 10 MHz. But I should mention that my logic analyzer is not an original Saleae, so who knows? Anyway it seems I sort of managed to fix the issue, by moving the lifted pin around. Maybe it was slightly bent towards one of the nearby pins and thus it was inducing noise in it? I once had a similar issue with the 50/60 Hz SNES mod, where it was working fine but I could see small sparks (!) between the lifted pin and an adjacent one. Actually I had already tried moving this pin around to no avail, I must have found the sweet spot now. Hope it lasts!
Just a short note to say that even now that my SMS2 seems to be back in business, the clock signals still look the same, so it's probably just some artifact of my cheapo logic analyzer clone.
