Re: Questions about pal clocks SX64

From: Nicolas Welte (
Date: 2001-11-22 16:55:55

Marko Mäkelä wrote:
> On Thu, 22 Nov 2001, Hársfalvi Levente wrote:
> > I'm sure the UltiMax does, but is it really the case with the SX-64? :-O
> > And if so, why?
> Remember the guy who asked repair instructions for his SX-64?  I think
> that discussion was forwarded to this list.  Or was it Raymond Carlsen who
> said that the SX-64 has a separate crystal module that contains two
> crystals (separate dot clock and colour clock)?

I can confirm this, but those crystals have the correct clock speeds. I can
only guess that they did this to save some space compared with the old four
chip clock circuit, but with a 8701 and a single crystal the board could be
rebuilt with the same space.

The SX64 has many more weird details in its construction. One of them is the
fact that the TOD clock runs off a separate 60Hz oscillator module, even in a
PAL machine. I always thought this was because the power supply is a switcher
and does not supply 9V AC. But it does, to feed external devices on the

Recently I had a dead SX power supply for repair, which was blowing fuses.
The repair was pretty easy, after I realised that one of the previous owners
tried to convert this 110V supply to 220V, and thought it would be enough to
change the transformer (which only produces 9V AC for the Userport and 15V AC
for starting up the main PS). The filter cap was only made for 150V and blew,
and so did the chopper transistor. So it needed a replacement transformer for
110V (the original one was gone), a cap and a transistor, and then it ran
happily from a 220 to 110V step-down transformer. 


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