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How to use SCART for our hobby
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).
Dodonpachinko:
Hello everyone,
I'm trying to build a DVI-I to SCART cable and would really appreciate if people who have experience with VGA to SCART cables could tell me if it would work.
It's really hard to find informations on these cables for some reasons and like Zebidee said there not one single wiring method.
Given that the traditional DVI-I to VGA adapters are passive, it's technically possible to create a DVI-I to SCART cable.
I used this VGA to SCART schema for wiring: https://imgur.com/a/F23Ckeu
I used this table for pinout correspondance: https://pinoutguide.com/Video/dvi_to_vga_adapter_pinout.shtml
I've come up with two solutions, one with MOLEX(5V+12V) and one with USB-A(5V only):
MOLEX: https://imgur.com/a/04Au5UV
USB: https://imgur.com/a/2KFW92F
I'd really appreciate some feedbacks before i try to build it.
Thank you!
Zebidee:
Both of those wiring schemas seem sound.
Some thoughts:
- Maybe easier to make a VGA-SCART cable and use that with a passive DVI-I to VGA adapter. This will give you more flexibility to use with other video cards.
- If still going DVI-I, it has 5v out on pin 14, and AFAIK this is standard for all. So you could use this for blanking instead of molex/USB? Ground is DVI pin 15.
- You probably won't need the 12v switching
- Run all your VGA RGB+sync grounds (5,6,7,8,10) together to one wire and a single SCART ground (choose whichever is convenient). For DVI-I end they're already joined.
- You could choose to run the blanking ground separately to SCART pin 18, though all these grounds are most probably joined at the TV end anyway (check it with your multimeter).
- You can combine the H+V syncs and then run that through a single resistor (470R to 1K). I've seen some people encountering signal reflection/interference when using multiple resistors, though this might only occur when they use different values for each.
- If you want to try composite sync (better than smushy) output from your PC/device, arrange it so you can easily disconnect the V sync wire (to avoid floating/ghost signals).
Unless it is important to you, leave the audio connections out to simplify. It is hard to fit everything into the SCART header/housing. Most TVs have separate audio inputs, and audio cables (3.5mm stereo to 2xRCA) are cheap to buy.
FYI Though they usually have two audio input jacks (often red/white), most TV speakers are wired for mono - the stereo inputs just get smashed together anyway. Makes sense when the speakers are only about 2-3 feet apart. Most TV speakers will also have considerable interference hum too, which isn't very obvious when watching video but more obvious when gaming. So, all things considered, you might choose to use some external speakers.
This all leaves you with only six wires to connect at the SCART end (R,G,B, H+V, switching, ground), seven if you run the switching ground separately.
Dodonpachinko:
Thank you for your response and your experience, it's very helpful!
I want to try this because i only have DVI and SCART cables at the moment...
We don't really know how good the connections are on those passive DVI to VGA adapters. They're often cheaply made and can become a point of failure in the line.
I tried to make a new schema taking account of your recommendations: https://imgur.com/a/IDJlwso
The C5 pin on DVI is analog GND. It's connected to the shields of each RGB wires. I don't know if TV need these but there is RGB return on pins 13-9-5 of the SCART and it correspond to DVI-I C5 pin(Analog GND).
What do you think?
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