I'm posting this guide in draft form in case there are some construction ideas in here that help others.
Also, here are some useful diagrams for anyone wanting to build their own VGA to SCART cable:
This guide will show you how to make a VGA to SCART cable that is compatible with both ATI and also Nvidia cards.
There are many VGA to SCART schematics to be found on the Internet.
The purpose of this guide is provide a step-by-step set of instructions that use photos instead of diagrams to show how the cable is constructed.
Audio cable with 3.5mm male plug
Preparing the VGA cable:
Tidy the rough end of the VGA cable (Fig. 1) by cutting a clean, straight line using a knife (Fig. 1a).
|Fig. 1a – Rough end|
|Fig. 2 - 50 mm mark|
Insert the plastic nut for SCART plug onto the onto the cable. It's very important to do this now before beginning to dress the VGA cable as it will be impossible to place this on after soldering begins. Next, cut a piece a 50 mm length of heatshrink that has a diameter large enough to fit over the cable. Choose a size that will also accommodate your audio cable later (10 mm should be sufficient). Slide this onto the cable end (Fig. 3).
|Fig. 4 – Outer insulation removed to expose shielding|
|Fig. 5 – Braid separated|
|Fig. 6a – Twisted braid wire|
|Fig. 7 – Foil removed|
First, identify the wires which look like the R, G and B lines. These will have shield wire wrapped around them (as in Fig. 7) or folded foil. Ignore these wires for the moment. Strip approximately 3 mm of insulation off the end of non-RGB wires. Then twist the ends of each to keep them neat (Fig. 8).
|Fig. 10 - VGA plug|
Top row: pins 1, 2, 3, 4, 5
Middle row: pins 6, 7, 8, 9, 10
Bottom row: pins 11, 12, 13, 14, 15
We need to discover the wires that correspond to the following pins:
Pin 5: (H-Sync ground)
Pin 9: (+5v)
Pin 13: (H-Sync)
Pin 14: (V-Sync)
Preparing the sync circuit:
Cut a piece of Veroboard to size. It will need to be 7 across and 9 down (Fig. 1a). Make sure you have orientation of the conductive strips correct (Fig. 1b).
Solder in the 3.3k resistor:
|Fig. 3a - 3.3k resistor|
|Fig. 3c - Top view|
|Fig. 4a - 68 ohm resistor|
|Fig. 4c - Top view|
|Fig. 5a - 1.2k resistor|
|Fig. 5c - Top view|
|Fig. 6a - 820 ohm resistor|
|Fig. 6c - Top view|
|Fig. 7a - BC548 transistor|
|Fig. 7c - Top view|
|Fig. 8a – Sync and ground wires|
|Fig. 8b - Top wire (yellow) is the composite sync output. Bottom wire (brown) is ground.|
Preparing the SCART plug:
Mount the SCART plug into a vice. Make sure to copy the orientation shown if Fig. 1a. Next, fill the R, G and B solder cups (Fig. 1b).
|Fig. 1b - Solder cups filled|
|Fig. 5 - RGB heatshrink applied|
|Fig. 7a - 68 ohm resistor in place|
|Fig. 7b - Heat shrink applied to +5v wire|
|Fig. 8a - H-Sync soldered (bottom right)|
|Fig. 8b - V-Sync soldered (3rd wire from top)|
|Fig. 8c - Composite sync soldered to SCART plug|
|Fig. 8d - Sync ground soldered to SCART plug|
Tin the ends