65XE PAL to NTSC mod
Posted: Thu Oct 07, 2021 8:49 am
I wanted live NTSC hardware for various tests. Since I couldn't buy an Atari or NTSC version, and I managed to get Antic and GTIA in NTSC version I decided to convert PAL to NTSC.
The 65XE board without ECI (i.e. revision CO70025) was placed under the soldering iron.
The remake is fairly straightforward, and the description in reverse order can also be applied to the rework in the opposite direction, so it might be useful to someone.
1. Desolder the Antic and GTIA systems, solder the sockets instead.
At this stage, the replacement of the Antic and GTIA systems alone allows you to determine whether the systems are operational, because in general, apart from the comments below, the computer is working normally.
a) Replacing Antic with the NTSC version only changes the aspect ratio, the colors remain the same as in the PAL version.
b) Replacing the GTIA with the NTSC version causes the colors to disappear and the image becomes black and white, because we still have a PAL clock on the disc.
2. Replace the quartz on 14.187576 with 14.31818
3. We throw out the PAL clock from colors.
In order to finally make the record NTSC exactly as it was produced in the factory, the following components must be discarded:
- quartz 4.433618
- 74LS74 integrated circuit
- resistors R69, R70, R71, R72, R73
- capacitors C58, C59, C60, C61, C111
- L8 coil
Simplified version: if we want to do the operation faster, and at the same time be able to do a quick return to PAL, it is enough:
- remove resistors R70, R72
- desolder Q6 transistor from the board
These treatments cut the PAL clock output from the GTIA and basically do the trick.
4. Solder the jumper in place of W2 (or the 0R resistor as it was in the original NTSC)
5. Regulation.
We'll have weird colors after reworking. In my case, everything was mostly pink and blue.
To set the right colors, we turn the potentiometer on the motherboard. At the same time note: in the case of PAL we are used to the fact that the colors change only a little, but with NTSC you can spin here by completely changing the palette.
It's best to run "Atari control picture". We shoot until we get the effect that the colors from the line "2" are the same as the colors from the line "F" and that they are shades of, say, brown and gold. Edit: then we shoot a bit further, to push the brown with "F" out of the palette.
It is not important what exactly these colors are, because they are a bit different on every Atari, but it is important where the "2" and "F" are repeated. If you set it like this, all games will look roughly correct.
How to repeat this color you can see by running the "Atari control picture" program in the Altirra emulator and switching the system to NTSC.
And that's it, we have an NTSC board that works as it should.
The 65XE board without ECI (i.e. revision CO70025) was placed under the soldering iron.
The remake is fairly straightforward, and the description in reverse order can also be applied to the rework in the opposite direction, so it might be useful to someone.
1. Desolder the Antic and GTIA systems, solder the sockets instead.
At this stage, the replacement of the Antic and GTIA systems alone allows you to determine whether the systems are operational, because in general, apart from the comments below, the computer is working normally.
a) Replacing Antic with the NTSC version only changes the aspect ratio, the colors remain the same as in the PAL version.
b) Replacing the GTIA with the NTSC version causes the colors to disappear and the image becomes black and white, because we still have a PAL clock on the disc.
2. Replace the quartz on 14.187576 with 14.31818
3. We throw out the PAL clock from colors.
In order to finally make the record NTSC exactly as it was produced in the factory, the following components must be discarded:
- quartz 4.433618
- 74LS74 integrated circuit
- resistors R69, R70, R71, R72, R73
- capacitors C58, C59, C60, C61, C111
- L8 coil
Simplified version: if we want to do the operation faster, and at the same time be able to do a quick return to PAL, it is enough:
- remove resistors R70, R72
- desolder Q6 transistor from the board
These treatments cut the PAL clock output from the GTIA and basically do the trick.
4. Solder the jumper in place of W2 (or the 0R resistor as it was in the original NTSC)
5. Regulation.
We'll have weird colors after reworking. In my case, everything was mostly pink and blue.
To set the right colors, we turn the potentiometer on the motherboard. At the same time note: in the case of PAL we are used to the fact that the colors change only a little, but with NTSC you can spin here by completely changing the palette.
It's best to run "Atari control picture". We shoot until we get the effect that the colors from the line "2" are the same as the colors from the line "F" and that they are shades of, say, brown and gold. Edit: then we shoot a bit further, to push the brown with "F" out of the palette.
It is not important what exactly these colors are, because they are a bit different on every Atari, but it is important where the "2" and "F" are repeated. If you set it like this, all games will look roughly correct.
How to repeat this color you can see by running the "Atari control picture" program in the Altirra emulator and switching the system to NTSC.
And that's it, we have an NTSC board that works as it should.