Sega Genesis 3, VA1, running in PAL mode?

Edit: sorry, its a VA2, the one with the jumpers to easily set 50/60 and English/Japanese.

I've changed the jumpers on the board to set the console to PAL, but it not work so well!

Having looked at the data sheet for the video chip (a Sony CXA1645M) it appears this chip has two pins that can be switched between PAL and NTSC... do these also need to be switched?

From memory, the Genesis 1 and 2 (Mega Drive in my case) needed a fixed crystal on the video chip for "PAL60" to work... is the Genesis 3 the same kinda deal? I haven't found anything mentioned about this?

Thanks!

 

Alrighty, I'm guessing this is the same as the Mega Drive 1 and 2.

Basically, the video chip gets a clock signal from the main crystal, divided by something, depending on if its NTSC or PAL.

The NTSC console has a 53.691Mhz oscillator, divided by 15, to get the 3.58Mhz video clock.

The PAL console has a 53.2034Mhz oscillator, divided by 12, to get the 4.43Mhz video clock.

Now, if you change the Genesis to PAL, it takes the NTSC oscillator (53.691Mhz) and divides it by the PAL's divider, of 12.... giving you a broken 4.47Mhz video clock...

I believe that feeding a fixed 4.43Mhz into pin 6 of the CXA1643 will correct this issue... but this still raises the question, what do the two other "PAL/NTSC" selectable pins on the chip actually do?

 

I've 50/60 jap/eng modded a genesis 3 va 2 a few days ago, here's the photos.

I removed the '0' resistors from r 22 and r 23, then connected the pins in the photo to centre of switches. I took +5v and gnd from another point under the pcb to avoid messing too much with tiny jumpers and wires.

worked at first attempt.

Never cared about pal color encoding as I use only rgb

 

I've ordered some 4.43Mhz crystal oscillators, so I'll see what happens when I feed the video chip a fixed clock frequency... I assume it will work, but I'm still not sure what the other PAL/NTSC pins on the IC do