As my original post on my DIY DVI to SCART cable is one of the most popular posts to date I thought I would expand a bit more on the details of making the cable. I did have some photos of the final product, but an unfortunate sequence of events occurred:

  • I took the photos on my mobile
  • I upgraded the firmware with a CyanogenMod build, which wipes the phone
  • I bought a new television and moved home so threw out the DVI to SCART cable I’d built as I could now use HDMI
    You could argue that is a fairly long winded sequence of events, but that’s normally how they go! Short answer decent, automated backups. I now let Google+ Instant Upload run and make sure I’ve got backups of all my photos as and when I take them.

Anyway, back to the DVI to SCART lead …

Parts List

My previous post contains more details about why everything is wired up the way it is. This post is just to give more detail about how the cable was put together.

Parts list:

  • DVI to VGA cable
  • SCART plug
  • Resistors – 3.3kΩ, 1.2kΩ, 820Ω, 270Ω, 220Ω, 68Ω
  • BC548B NPN transistor
  • LM317 voltage stepper in a TO-92 case
  • Breadboard
  • Electrical tape
  • Small Plastic Enclosure – I used one from Maplin
  • Connecting wires

Connection Diagram

Tracing out the wire to pin mapping for the DVI to VGA cable was pretty tedious and just required some patience a piece of paper and a multimeter. Once that was done it’s pretty straightforward to figure out what needs to be connected to what.

This wiring diagram shows how it all hangs together. To make the diagram clearer I’ve treated the voltage stepper and sync combining circuits as a black box. Further down this post you can see the details of those two circuits.

Breadboard Wiring for combining sync

There were two circuits used to make this cable. The first one is used to combine the HSync and VSync pulses from the VGA signal into a single Composite Sync signal. All credit for this circuit goes to The Nexus.

The schematic for my breadboard wiring looked like:

The horizontal lines are the conductive rails of the breadboard and the red circles are where the components are soldered onto the breadboard.

The component values were (all as per the original):

Component Type
R1 3.3kΩ
R2 1.2kΩ
R3 820Ω
R4 68Ω
Q1 BC548B

Breadboard Wiring for voltage stepping

The second circuit is used to step the voltage down for the RGB signalling on pin 16.

The schematic for my breadboard wiring looked like:

The component values were:

Component Type
R1 220Ω
R2 270kΩ

2 thoughts on “DIY DVI to SCART cable revisited

  1. Hi Mark,

    I’ve been bashing my head against my computer for a few days trying to do this and just saw your site which seems to have achieved what I am trying to – the electronics is not the problem for me, its the xorg setup. I’m using XBMCbuntu and have put mode lines in etc but have various problems like X ignoring them and refusing to start. Could you tell me what your software configuration is and do you think it would work with a stock XBMCbuntu install with modified /etc/X11/xorg.conf or did you have to use a more modified X setup?

    Thanks, Pete

    • A couple of things spring to mind to check.

      Firstly when the X server doesn’t start are there any obvious errors in /var/log/Xorg.0.log?

      One thing I did have to do was change the HorizSync and VertRefresh ranges in the Monitor section to be low enough for the interlaced modes to be valid. You can get the X server to log its mode validations during startup – add Option "ModeDebug" "TRUE" to the Monitors section. This will put a lot of extra information into the Xorg.0.log file and should hopefully give you some hints as to why the mode is not being accepted – if indeed that is the problem.

      Good luck!


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