pal ntsc nes with dual ppu/cpu set and switch

Started by prince tomato, February 27, 2017, 01:14:32 pm

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prince tomato

hi again folks,

recently i dug up a PAL NES that someone gave me once,
but i hardly play NES carts, and i only use NTSC consoles,
so i didn't have much use for it.
but most of my friends here (Netherlands) play pal NES's and games exclusively, at most they will play NTSC games on a PAL console with disabled CIC lockout chip.

so, i replaced a PAL PPU/CPU and Xtal with an NTSC set once in a PAL Famiclone, which made it a very nice NTSC model.
but, would it be possible to use both sets and switch between PAL and NTSC?
i thought just hooking both up and feeding either the PAL set or the NTSC set 5v on the correct pin would do the trick.

so i lifted the 5v pin from the PAL CPU and PPU,
piggibacked the NTSC set on top of the PAL chips i used a UMC UA6527 CPU, and a 2C02 E PPU),
except for the 5v pin, which i left floating on all four chips to solder the wires for the switch to.
i lifted one pin from the PAL Xtal, soldered one leg of the NTSC Xtal to the other leg, and left both other legs floating for the switch as well,
and wired everything to a 3pole single throw switch,
so when i switch, either the NTSC set gets 5v, or the PAL set.
i am not sure if the Xtal has a certain polarity that i should be aware of,
but it doesn't work.
i only get a solid white screen in both switchpositions,
although in NTSC mode the screen becomes visibly larger, so something is going right.
is there any other signal i should (dis)connect?
any help or experience in similar experiments are very welcome.


FAMICOM_87

better use NOAC for this mod
in it you have NTSC and PAL inside,  only you have to add 2 Xtals and have to find where is the pins to swetch between PAL and NTSC  :)