Steps needed to convert a Amiga 1000 NTSC to PAL:

1. Replace NTSC Agnus 8361 with a PAL Agnus 8367, the Amiga 1000 has the old Agnus chip which cannot switch between NTSC and PAL.


 

2. Change oscillator inside the shielded case from 28.63636MHz to 28.37516MHz.


 
3. Step down transformer (220V to 110V) for the PSU, the 50/60 Hz tick signal is derived from the mains power.

 

4. Swap components for the video circuitry according to the service(ALR) manual to get PAL signal on the composite out. This step is not necessary as you will get a proper video signal through the RGB port. If you decide to skip this step the built in composite video output signal will either be B/W or your monitor will not be able to display the signal.

The schematics for step 4 which I found were a bit challenging to interpret so I traced and redrew that part. It turned out my NTSC REV 6 motherboard does not have the option to convert to PAL composite output. Component names also differ from the chart.

 

 

Images courtesy of Amiga Hardware Database

Left PCB is PAL with placeholders for NTSC components R46, R57, R58 and jumper “20”. Components for PAL (R206 and C215) are located just below the MC1377.

Right PCB is NTSC composite only with no option to convert to PAL as there is no location for R206 and C215. It’s neither possible to “un-ground” pin 20 which is the PAL/NTSC signal setting for the MC1377.

 

Amiga 520 Schematic
The 520 (PAL) Modulator schematic was useful in the process as it also uses the MC1377.

Schematic from Dave’s Amiga Hardware Page