PAL amiga in US, help!!!!

[tonyw]

It probably won't work. You will have to change the crystal as well. There are several differences between PAL and NTSC:
Horiz freq: PAL15625 NTSC 15750
Vert Freq: PAL 50 NSTC 60
Colour encoding: different (what the link selects)
Colour frequency PAL 4.43361875 NTSC 3.58-something.

Most TVs will display the different H and V signals withour problems, and some will switch colour automatically, too. But if it's a fixed frequency colour set, you've got to have the PAL/NTSC switching right as well as the frequency.

The colour frequency comes from the crystal in the computer. PAL Amigas have a crystal of about 29 MHz, NTSC are 28 MHz. You'll have to change that as well, unless the TV is clever.

tony

[tonyw]

@McIlwrath
" As I understand it, the rest of the frequencies are generated by the chipset, so that's why a simple pin on the Alice should do the trick."

I'm afraid that you are mistaken. The chipset only divides the system clock by various numbers to derive all its output and internal clocks. So the 7/14 MHz bus clock, the video scan clocks (50 H & 15 k) and the colour subcarrier clock (3.58 / 4.43 MHz) are all derived from the 28 or 29 MHz master oscillator.
Changing the link can alter things like colour subcarrier phase swapping (PAL/NTSC) and division ratio (x8 for NTSC or x6.666 for PAL) but the master clock still needs to be changed slightly to get the right frequency. The chip can't do that.
The same circuitry was used in the C64, C128 and Amiga 1000, albeit integrated into the Agnus chip. I would guess it's the same logic in the A1200. It uses the minimum of hardware to do the job and the chip can also put out the bus clock (which in the C64 and A1000 depended on whether you had a PAL or NTSC crystal).

tony