Problem 2: no color -Re: Vertical Sync Issues with modern TV

[Mike Willegal <mike@willegal-nospamplease.net>]

Ok,
   Those old boards were designed to work as PAL or NTSC.  Cut a couple 
of traces and add some blobs of solder to convert.  Didn't notice the 
difference until I compared it to a "working" NTSC board. 

   New Problem:
 I've changed the  board back to NTSC, but now I don't get any color.   
Tried two different TVs and an RF modulator.  My other board of the same 
vintage also doesn't exhibit any sign of color, either, though it never 
had the issue with PAL sync timing.   I do get shades of grey.
   
   I don't believe it showed color before I made the changes to NTSC, 
but am not positive, since my focus was on vertical sync problem and the 
monitor I usually use is only monichome.

   Any ideas on this one, before I borrow the Oscilliscope, once again.

   Regards,
   Mike Willegal


In article <20040923120323.07582.00001013@mb-m11.aol.com>,
 mjmahon@aol.com (Michael J. Mahon) wrote:

> Mike Willegal replied:
> 
> >In article <20040921013815.23955.00000873@mb-m16.aol.com>,
> > mjmahon@aol.com (Michael J. Mahon) wrote:
> >
> >> Mike Willegal wrote:
> >> 
> >> >   My Apple II's seem to work fine with the old Taxon monochrome monitor 
> >> >I have, but vertical sync appears to be an issue with recent color TVs 
> >> >(with no apparent external vetical sync controls).  Tried both an RF 
> >> >modulator and composite video, but vertical sync  doesn't lock on two 
> >> >different TVs.
> >> >   Any ideas?
> >> 
> >> It's unlikely to be a scan frequency problem, since the Apple is
> >> very close to standard.
> 
> <snip>
> 
> >This is getting more interesting.  It appears from an Oscilliscope that 
> >the vertical refresh is cycling at 50 HZ.  The board came from ebay - 
> >and is marked copyright 1978.  Did apple make a PAL type board in that 
> >timeframe.  There is no rework visible, so it either has a strange 
> >problem in the ls161 dividers area or was built for a PAL type 
> >application.  It came with a PAL encoder board and a universal power 
> >supply.
> >
> >The Taxon Monitor must be very tolerant of veritcal refresh rates.
> 
> Most monitors are adjustable in the 50-60 Hz range, though not all.
> 
> >What do you guys think?
> 
> I think you have a remarkable Apple II.  ;-)
> 
> It does sound like PAL scan rates--perhaps you have a very early one.
> Someone from across the pond would know...
> 
> -michael
> 
> Check out parallel computing for 8-bit Apples on my
> Home page:  http://members.aol.com/MJMahon/