Date   : Wed, 26 Feb 2003 17:25:14 +0000 (GMT)
From   : Sprow <info@...>
Subject: Re: Master 128 on a TFT flat screen???

In article <20030226144552.O94825-100000@...>,
   Brian Widdas <brian@...> wrote:

> On Wed, 26 Feb 2003, Richard Gellman wrote:

> > >Anyone ever attempt using a Master 128 with a PC monitor thru somekind 
> > > of Video to SVGA adapter? 

> > I believe, for compatibility reasons, the BBC Micros output a picture 
> > that
> > conforms to TV standards, such that the picture can be output on UHF,
> > Composite, and RGB without the need for extra translation electronics. Im
> > not sure of line frequency, but the field frequency would be a TV 
> > standard 50Hz.
>
> Indeed.
>
> The RGB signal is at TTL levels, though - the monitor would most likely
> get very upset by it.

3 series IN4148 diodes will bin all that and get you down to nearer 1v,but
conversely you should remember the monitor is probably presenting a 75R load
which the TTL in the beeb logic wont be expecting.

> Also, I believe a VGA signal uses separate horizontal and vertical sync
> lines, whereas the BBC's sync output is composite, so you'd need to
> arrange a sync-splitter.

It's a shame,because the syncs are available inside the BBC seperate - you
just never see them on the external connectors.

> If there's an online archive of Mike Cook's Body Build articles anywhere,
> I believe he covered BBC->VGA converters back in the days of The Micro
> User.

I'd have thought the biggest hurdle these days is finding a monitor which
will scan as low as 50Hz/15.625kHz field and line rates,
Sprow.