Date   : Fri, 07 Apr 2006 13:01:18 +0100 (BST)
From   : Chris Johns <chris@...>
Subject: Re: Using an AKF30 with a Beeb

On Fri, 7 Apr 2006, Fragula wrote:

> CGA also has split syncs, not insurmountable, but a PITA, and *if my
> memory works at all* is TTL. Sounds good? Well not really.. it has a
> seperate "brightness" TTL input. (at this point i'm not entirely sure
> whether i'm confusing it with some even older standard).

Was "brightness" (intensity) part of the slighty later EGA? I thought CGA
was only 4 of 8 colours (did EGA had a 15 colours? the basic 8 plus
"bright" version of 7 of them (given bright black is still black).

> I wouldn't have expected it to have a 60Hz output for starters, or for
> that matter, TTL inputs, as IIRC even the earliers arcs had a 256 colour
> mode, and the compost out works with a standard TV set?

Old arcs generated 50Hz RGB (at least to the best of my knowledge they
did). This changed with the A4/A5000, which could do VGA too (at 60hz,
which could do odd things to your sound, as the VIDC was used for both
video and audio).

> analog monitor usually is happiest with just under a volt. You would
> also probably need to split the H&V syncs somehow. Not terribly
> difficult, but a small electronics project rather than just a cable.

No need to split H&V sync. The old archimdedes machines generated
composite sync.

I suspect a resistor on each line would be all that's required, if the
monitor doesn't have a digital (TTL) input. I have some old archimedes
screens here that have a SCART socket (for an arc) and a DIN socket for a
beeb.

I have an old RM Nimbus EGA monitor somewhere too, I had it connected to a
master compact for a while, which a bit of a hacky connection to get the
seperate HSync and VSync out from the CRTC. I should build a sync
seperator for it really.

Cheers

Chris
-- 
 Chris Johns <chris@...             >