I like that
syboxez came here with a solution and asked for criticism and verification. I respect
maxtherabbit's contributions but no one's being critical. Just accepting the first thing that seems to work and not considering the trade offs. Increasing the stock value of C11 by a factor of 10 to fix jailbars but in turn causing black bars in some games is good example.
Reading over the TurboGrafx 16 / PC Engine fix, he recommends replacing one 0.1 µF capacitor each in the analog and digital blocks of four with one 47x higher. Reduces resonant frequency by about 3.5x if same ESL. I judge by the write up that not all consoles have jailbars. More a symptom of an aging electronic device.
Here the proposed solution is replacing almost every AC decoupling capacitor at each chip with one 100x greater. If you want to uniformly reduce EMI, could try EMI shielding tape or EMI cages first. Aluminum foil wrapped completely with duct tape to prevent a short would be an okay budget attempt. I have to doubt that jailbars are caused by ripple voltage at each and every chip.
I think the strategy should be to measure voltage levels and slew rates from each chip on a console with no jailbars, then replace capacitors with same values and measure, then compare against another console of same hardware revision that has jailbars. Show the operating frequencies of the chips on oscilloscope, calculate the resonant frequency of the capacitor block around them and make Bode plots before and after signal passes through the block.
An ideal AC decoupling capacitor block allows the chip's square waves or analog signal through and filters out the noise. I don't want to say increasing Ceq by 100x is crazy when it seems to work but you reduce the resonant frequency by a factor of 10x, assuming same ESL.
Did Nintendo settle for 0.1 µF because, as Tim W suggested, higher valued ones didn't exist at 0603 / 0805 size in the 90s? Without theorizing too hard, jailbars could be from unfiltered harmonics that get into the ~3.58 MHz NTSC color burst. PAL could be completely unaffected.
D-Do German speakers realize the double entendre? No complaints.