Software Support > GroovyMAME
Black and white picture with VGA to SCART RGB adapter
asdf015:
Hello,
I have bought a VGA to SCART adapter (Vga2Scart sync converter from retro-upgrades) to use with CRT emudriver, but I'm only getting a black and white picture.
Here's what I have tried so far:
- Three different older and newer Radeon graphics cards connected via DVI-I, VGA and HDMI
- Tested CRT emudriver on Windows XP, 7 and 10
- Opened the SCART cable to make sure it's fully wired
- SCART pin 16 (RGB select) is at 1.5V. When I set it to 0V (composite video mode), I get a black screen.
- SCART RGB output pins on the Vga2Scart adapter seem to be working properly (each 0.53V on a fully green/red/blue screen)
- Changed the color options in the ATI control panel, it's getting lighter and darker but still no colors.
My TV is an LG Flatron RE-21FB50RX from 2003.
Before this, I had been using an Nvidia Geforce 6700 XL graphics card with native SCART RGB output, so I believe that my TV supports RGB over SCART. I have also tried removing the individual SCART RGB pins one by one, this makes the respective color on the screen go black, confirming that the TV is operating in RGB mode.
I have asked the seller of the Vga2Scart adapter, they have not heard of this problem but suggested that I try 50hz instead of 60hz, that didn't help sadly.
Does anyone know what could be the problem?
asdf015:
I did another test: I created some RGB test images that I displayed full screen, and then I measured the RGB pin voltages at the SCART socket.
The first test image consists of all three RGB colors at once in columns, and then I created three more test images that consist of just one individual color.
The voltages that came from the Nvidia card were 0.2v on each RGB pin for the three-column image, and 0.55v on each pin for the individual color test images. The voltages from the CRT emudriver PC were almost the same (0.18v for the three-column image, 0.53v for the individual color images).
I just don't understand why the TV does not show the colors if it's receiving the same input signal from both PCs.
lilshawn:
https://retrogamingcables.co.uk/Black-and-white-image-on-tv-when-using-an-RGB-SCART-cable
asdf015:
--- Quote from: lilshawn on July 04, 2024, 08:13:18 pm ---https://retrogamingcables.co.uk/Black-and-white-image-on-tv-when-using-an-RGB-SCART-cable
--- End quote ---
Thanks. I went through the reasons listed there, but none of these seem to apply. The TV is in RGB mode, and the picture displayed cannot be a composite or s-video signal because they simply do not exist in the VGA signal that comes from the PC.
The cable is in the correct SCART socket (there is only one) and manual video format switching is not possible.
lilshawn:
it's going to be hard to diagnose without knowing more about... well... everything.
where are you located? north america? south america? china? Europe? Australia?
where did this TV come from? local? imported? USA? Europe? Japan?
what is this TV's normal native signal format? PAL/NTSC/SECAM?
can you switch formats though tv's menu or other such setting?
what resolution are you trying to feed in? is the TV capable of such a resolution? is it too high? is it too low?
what adapter or cable are you using?
what are its capabilities?
is there any configuration that needs to be done to it?
scart can be notoriously difficult to get working properly, and it usually is due to region incompatibilities (50 vs 60 hz signal rates in NTSC vs PAL regions) tv's with specific input requirements (only being able to accept specific types of sync signals) and the "automatic" signal sourcing and configuration by the host device by having specific voltages on specific pins (like pin 8 and pin 16) there may also be incompatibilities depending on the specific revision of scart your TV has and possibly how many scart ports it has. one or more may not be capable of certain resolutions or video signals or sync signals depending on which it has... (as well as a possible difference in capabilities of the various scart ports (if it has multiple, which is not in your case anyway...but i include it for the sake of completion)) not to mention the half dozen types of cables there are and that are meant to be used depending on what kind of connection you are making.) to add even MORE convolution, a tv from japan (even though it has the same 21 pin connector as SCART) has it's own version called JP-21 with it's own pinout. This format was abandoned around 2003 (the same year as your TV's production) so it's not really common.(since your image is black and white and not "red", which is a typical issue when using a regular scart and cable with a JP-21 port... this is also not the case for your issue... but i also include this for the sake of completion)
i guess the first thing for you to do is start at the start of the signal and make sure your computer is outputting the proper resolution and frequency that your TV is capable of...and either switching the signal or your TV settings to match each other (tv service menu?)... as well as the capabilities of the scart cable/adapter or whatever.
(so ntsc/pal 50hz/60hz etc. and so on and so forth.) as long as all the signalling matches appropriately for what the signal is and the scart is telling the TV (via it's config voltages on the 8 and 16 pins), it should display it properly. Pin 8, the switch signal pin, carries a DC voltage from the source that indicates the type of video present.
typically for the switching signals...
for pin 8...
0 V–2 V means no signal, or internal bypass
4.5 V–7 V (usually 6 V) means a widescreen (16:9) signal
9.5 V–12 V (usually 12 V) means 4:3 signal
so you should have 12v on pin 8 to force the tv input to 4:3 mode since your TV is 4:3 format
for Pin 16, (the blanking signal pin), carries a signal from the source that indicates that the signal is either RGB or composite.
0 V–0.4 V means composite.
1 V–3 V (nominal 1 V) means RGB only.
i'm unsure if having 5v on this pin, as you've indicated, has any negative repercussions.. probably not... but who knows with regard to you particular tv.
your cable or adapter you have should have a circuit to combine the sync signals from your VGA input (Combine RGBHV to RGBs) since the SCART protocol does not support separated sync, only combined or "composite" sync which is a horizontal and vertical sync in one signal. and example is shown here: https://ultimatemister.com/product/ultimate-vga-to-scart/
hope this helps
Navigation
[0] Message Index
[#] Next page
Go to full version