Date   : Sun, 11 Jan 1998 13:38:48 GMT
From   : Chris Thornley <osu036@...>
Subject: Re: How do I make Beeb video stable on 60 Hz?

The monitor your using what make is it?
Is it a CGA monitor or a monitor from the USA?
The CGA and RGB monitors use a vertical frequencey of 60Hz instead of 50Hz
and your monitor mighth no be 
doing a good job of locking on to this. Usally inside a monitor is preset
trimers which can be altered to variery 
the line frequency and vertical frequency. A tv technitions is best to see
about this modification as there are a 
lot of live voltages in there.
Hope this helps.

On 19 Dec 1997 14:11 EST Arlen Michaels wrote:

> From: Arlen Michaels <amichael@...>
> Date: 19 Dec 1997 14:11 EST
> Subject: Re: [BBC-Micro] How do I make Beeb video stable on 60 Hz?
> To: mike@...
> Cc: bbc-micro@...
> 
> In message "Re: [BBC-Micro] How do I make Beeb video stable on 60 Hz?", 
> 'mike@...' writes:
> 
> >In article <199712161656.QAA01508@...>, Arlen Michaels
> ><amichael@...> writes
> >
> >>Can anyone help with this one?  My BBC Model B makes a slightly jittery
> >>display when I connect my RGB monitor.  The Beeb was originally used in
> >>Scotland but now I'm running it here in Canada where we have 60 Hz mains
> >>power, and I suspect there's a 50 Hz timing dependency that I've got to
> >>change. Is there a software or hardware patch I need?
> >
> >The mains frequency won't make any difference when running on a RGB
> >monitor.  What you are probably seeing is the Mode 7 interlace, which is
> >worse on some monitors.  Some top-of the range CGA monitors even had a
> >control to reduce the jittery effects caused by interlace.  If you type
> >
> >*TV 0,1
> >MODE 1
> >
> >does the jitter stop?
> >
> >You can turn off interlace in Mode 7 with the following:
> >
> >VDU 23,0,8,144,0,0,0,0,0,0,0,0,0,23,0,9,9,0,0,0,0,0,0,0,0,0 
> >
> >but that spoils the nice rounded Mode 7 font.
> >
> >-- 
> >Mike Tomlinson
> >
> 
> Thank you Mike, I will try this.
> Arlen
> 

               />      Christopher J. Thornley is OSU036@...
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