Re: Difference in luma-chroma delay of C64/C128 compared to standard S-video

From: Gerrit Heitsch <gerrit_at_laosinh.s.bawue.de>
Date: Wed, 6 Sep 2017 15:34:34 +0200
Message-ID: <5921ad47-28f7-fa2e-8e29-4eeb2801cf48@laosinh.s.bawue.de>
On 09/06/2017 03:19 PM, Mia Magnusson wrote:
> 
> Also I found some stuff on the net about improving the picture by
> changing stuff in the RF modulator. Maybe that might be an option too.
> Although the picture is sharp enough to not give any readability
> problems at all it would be nice to have a picture as sharp as
> possible (without overshoots). :)

I found this circuit to give a nice, sharp picture on my 1084 CRT:



Video amp for TED or VIC-II. To be used in place of the RF
modulator, generating better signal quality.

Note: This circuit removes the CVBS output! It's Y/C only!

                    ___ R1
   chroma in  -----|___|---+     +5V
                           |      |
                           |      |
                    R2     |      |
                    ___    |    |/
              +----|___|---*----|  T1
              |                 |\
              |   R4        R3    V
              |   ___       ___   |
              *--|___|--*--|___|--+
              |         |
              |         |        || C1
             ---        +--------||---------- chroma out
             GND                 ||

              D1       R5    +5V
                       ___   |
   luma in ---|<|--*--|___|--*-------------------+
                   |         |                   |
                   |         |                   |
                   |       |/                   ===  C2
                   +-------|  T2                 |
                           |\                    |
                             V                   |
                             |   R6        R7    |
                             |   ___       ___   |
                             +--|___|--*--|___|--*
                                       |         |
                                       |        ---
                                       |        GND
                                       |
                                       +--------- luma out


  T1 = T2 = BC547B
  D1      = 1N4148
  R1 = R2 = 510 Ohm
  R3      = 68  Ohm
  R4      = 270 Oh
  R5      = 470 Ohm (if 6569, use 1 KOhm for TED and 8565)
  R6 = R7 = 150 Ohm
  C1      = 1nF
  C2      = 100nF

Do _not_ use metal film resistors, keep connections short.

luma in    = pin 23 on TED, pin 15 on VIC-II
chroma in  = pin 13 on TED, pin 14 on VIC-II

luma out   = pin 1 on video output
chroma out = pin 6 on video output

Use a clean +5V supply, not the C64 main supply. A 78L05 will work.

Might still need 330 Ohm series resistor for Chroma.

  Gerrit




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Received on 2017-09-06 14:03:45

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