This may sound strange, and sometime the exposed reason is “bad quality cable”: some RGB cables may not actualy display RGB signal on a Real CRT TV. The cable can be of a good quality, but I found multiple times RGB SCART cables that shown only composite signal even if the console had native RGB output.
This problem is due to a missing switching signal…
The SCART standard
The RGB signal provide obviously a far better image than a composite signal, but I saw from time to time people who was blaming the cable quality and / or the console output. In fact, without the proper RGB blanking signal, a CRT TV still display the console output through the composite wire, even if all RGB signals are present. The composite signal is often present at the same time as RGB, because the composite signal usualy also serves as CSync when using RGB mode.
That why you may have a blurry / bad quality image even if you use an RGB cable.
To understand what is the blanking signal, the SCART standard is explained on wikipedia : https://en.wikipedia.org/wiki/SCART
An easy way to detect wether a cable has a correct blanking signal is if your TV is actually not compatible with NTSC composite : in that case, the video output will show black and white image even if the source has a native RGB output. As all my consoles are japaneses or american models, they all output NTSC signal, so I can easily check my video cables.
Bad or missing blanking signal
The photo below shows a Playstation RGB cable from Aliexpress, without anything wired on pin 16
And here is the display I get with my japanese PSOne using this cable : composite signal in black and white (my TV does not support NTSC composite) :
Good or corrected blanking
To get the correct RGB blanking signal, a simple resistor (values from 50 to 280 ohms are fine) between pins 8 and 16 can do the trick. The resitor make a divider bridge with the TV input impedance of 75 ohms, thus providing between 1V and 3V to pin 16, so the TV correctly switches to RGB mode.
Below is the same cable, but with the resistor soldered between pins 8 and 16:
The same Japanese PSOne with the modified cable : it is now in RGB, in colors :
If your CRT TV is compatible with NTSC composite signal and you use such a cable without any blanking signal, you may actually see composite output instead of clean RGB.
It may be worth checking 🙂
