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How to use SCART for our hobby

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ckong:
 Never mind

:cheers:

Zebidee:
I decided to update this thread slightly. I was just messaging a European member about VGA-SCART construction, so decided to post here as well, recycle the words ;)

My own understanding of making these cables has evolved over the years. I've made dozens in my time, using different techniques. So I thought it worth posting some tips n tricks.

There are different ways to build these cables, no single way the best. The differences mostly come down to the sync and blanking.

Obviously you run your RGB into pins 15,11,7. Video grounds can all be joined together, any ground pin will do. Ground the 5v/12v to a different ground pin.

Sync goes to pin 20. VGA sync voltage (~4 - 5v) is too high for TVs (~0.3v - 1v), so you want to use a resistor (470R to 1K) on the sync input. You can:
- just twist the sync wires (VGA 13+14) together and run that wire through the resistor.
- Alternatively, you can just connect VGA 13 (H sync), via resistor, but then you must setup composite sync with CRTEMU/VMMaker or whatever you are using.
- Another alternative is to use a pair of Dupont connectors for the Vsync (pin 14) connection, so you can disconnect if running with composite sync out of CRTEMU.

I suggest using a single resistor on sync, rather than two resistors (one on each H+V lines). Using two resistors can cause signal reflection interference.

Twisting the wires together is simple, gets you "smushy" csync, which will probably work for most CRT TVs but not all. It is pretty good but not perfect, there may also be some visible artifacting from smushy sync, like a little zigzag at top of screen. Might not matter for many people. Different TVs show different things. Some TVs might lose csync every few seconds.

Csync output from CRTEMU is usually better than smushy sync. It comes out on VGA 13 (Hsync) only. However, if pin 14 (Vsync) is still connected then you may get some interference (the line voltage is able to "float", sometime causing false signals). So, best to remove Vsync connection completely if running with CRTEMU Csync.

For the blanking voltage, best to take input from PC via standard PSU MOLEX connector (with 4 pins). If your PC has only SATA then buy a SATA-MOLEX adapter (or make one :D). You can get both 5v and 12v from MOLEX. You only need to connect one of the grounds.

Take the 5v via resistor (150-200R) to pin 16 for blanking. When connected to TV, which is 75 ohm terminated, this will divide the voltage, giving you ~1.5v - 2v blanking signal.

Optionally, you can also take the 12v directly to pin 8 to autoswitch the TV into AV mode. Only some TVs need this, many will stay in AV mode after powering off/on again. You may be able to control this via service menu. Also pretty easy to press the AV button on remote or front panel. However, it can be handy if you are mounting a TV inside a cab, and need the TV to autoswitch into AV mode when powering on.

I use female spade crimp connectors (2.8mm) + heat shrink tubing, which means less soldering. It works with both the "spade" and "bucket" pin-type SCART header designs. This really is the easy way to do it. Also means you can remove wires from pins as needed, like when you realise you've forgotten to put the locking ring on first!    :banghead:

If using the female spade connector trick, you will need to break off the last pair of "wings" (that lock the wire down) for it to fit inside the SCART housing. Lightly rub down the broken end with a file or sandpaper to remove any sharp bits. You will also need to bend the necks a bit (match the angle of the SCART header).

 


 

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