Date   : Mon, 25 May 2009 11:51:23 +0100
From   : francis@... (Francis Devereux)
Subject: S-Video mod for Master 128

Hi all,

A while ago I promised Steve that I'd provide details of what I've  
done to get S-Video out of my Master.  My mod is based on guesswork  
and experimentation, so I'd appreciate it if anyone can tell me  
whether what I've done is safe or whether it could cause any damage...

Here's what I did:
Attached one pin of a 470pf capacitor to the emitter leg of Q12 and  
the other to pin 4 of the S-Video socket.
Attached the centre of the back of the composite video socket to pin 3  
of the S-Video socket.
Attached the outside (ground) of the composite video socket to pins 1  
and 2 of the S-Video socket.

I used a S-Video socket from Maplins (code PL55K) and a short length  
of coax cable running out of the back of the Master's case to allow  
the S-Video out to be used with the case closed.  There's a pic at http://www.devrx.org/hardware/bbc/m128_svideo.jpg

This works with the S-Video input of my Dell 2408WFP monitor, and the  
picture is better than composite with the colour mod. However:
  - The picture still isn't as good as RGB connected to my AKF18  
monitor or a TV via RGB SCART.
  - There is massive input lag on the 2408WFP's S-Video in, making it  
unsuitable for games.  I think that this must be something to do with  
it's S-Video processing because I don't notice much input lag when  
using the DVI in.
  - With the S-Video mod in place, the composite video out looks noisy  
(can anyone explain why?).

Francis