Modifying SX-64 from NTSC to PAL

From: Marko Mäkelä (
Date: 2001-05-03 10:29:08

Dear Alex,

> And yes, it has two crystal and a subboard for dividing I think.

The schematic 251103, right side, features a "clock unit" as a "black
box" with the following pinout:

1 ground
2 dot clock (8*phi0)
3 bus clock (phi0)
4 +5V
5 ground
6 color clock (phi color)

In the table below this "black box" in the schematic, the figures for dot
clock and color clock are swapped.

> So it gets more complicated than a normal C64...

As I don't have an SX-64 or the schematics for this subboard, I'm passing
a copy of this message to the cbm-hackers mailing list.  If there are no
PAL SX-64 owners on the list who could help you, you could try to
construct some sort of a schematic diagram for the subboard (even just the
part numbers would help a lot).


I left the following as additional information for the cbm-hackers crowd:

> Here´s a text from Ray that could make you see better the situation... :)
> ------------------------------------------------------------------------
> Alex, 
> The more I dig into this problem, the more I realize a conversion is
> just not that common, but there certainly are PAL SX64 computers out
> there. I'll give you the information I have based on this hand drawn
> Commodore service manual. I'll have to agree that there are no
> jumpers... at least none that I could find. However, it appears there
> are several chips that need to be changed, and the master oscillator
> is a sub board with a crystal on it. Changing to PAL might require
> changing that entire board which this book identifies simply as "clock
> unit"... no numbers. The book doesn't show a diagram of that board,
> but it appears to be a master oscillator and a set of dividers to
> generate the three clock signals. It also appears the NTSC PLA chip
> UE4 (numbered MB112A101) needs to be changed to a special PAL version
> (numbered 7700-001). With the wrong clock signals, you will have
> incorrect colors out of the VIC. It doesn't look like an easy mod. Two
> people that regularly post to the newsgroup comp.sys.cbm are Nicolas
> Welte and Marko Makela. They are both engineering techs that know the
> inner workings of the computers much better than I do (I'm just a
> repair tech) and would be able to tell you exactly what you need to
> know to do that modification. They live in Europe and would have the
> PAL versions of the SX anyway. I've only seen the NTSC version myself.
> Good luck!
> Ray

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