Newbie question: Sync problems when connecting to TV/Monitor

[Eratosthenes]

Not sure if I got you?

What needs to be done that the signal will become darker?

[antoniovillena]

Not sure if I got you?

What needs to be done that the signal will become darker?

Just connect directly the RGB signals. The problem is that normal signal is adapted to a 75 ohm load. But the AD724 chip has is own 75 ohm load and you have 2 resistors in parallel, so the signal is lowered (so darker). Now in your scart cable you have transistors that put a low ouptut impedance so the signal is not lowered.

[Eratosthenes]

OK, I will check this and (temporarily) remove the transistors...

Thanks once more for the info.

P.S.: If it works I will put a video online showing the difference...

[antoniovillena]

Put wires in the lines marked with thick black line

[Eratosthenes]

Jep! - I will remove this.

Is it added to the SCART plug or to the VGA housing of the cable?

P.S.: If I add this patch: transistors are futile (custom Star Trek-stuff... )
P^2.S.: As I've got a ZX-UNO 2M VGA, maybe the problem it's somehow different, isn't it?

[ManuFerHi]

The RGB signal is 100%, same as VGA, it has a VGA 2M model. The cable is passive. I think it's some kind of incompatibility with your TV, before sending your unit I was testing it with the same cable and it worked well.
this problem only appears in the Spectrum core?

[antoniovillena]

Jep! - I will remove this.

Is it added to the SCART plug or to the VGA housing of the cable?

P.S.: If I add this patch: transistors are futile (custom Star Trek-stuff... )
P^2.S.: As I've got a ZX-UNO 2M VGA, maybe the problem it's somehow different, isn't it?

Yes. In this model your cable is passive. There are no transistors. The problem is other.

[Eratosthenes]

As the TV is working "perfectly well" with different RGB devices I think the problem is part of the signal of the ZX-UNO...

As mentioned before I will do some measurement and try a lower signal level.

Have a good night.

MfG
der Eratosthenes

[Eratosthenes]

Hello!

Finally I found the reason why the TV doesn't work!

It's because "sync on green is missing". - What I've done is adding the sync signal (pin 20) to green (pin11) via a 100ohm resistor.

This is definitely not the best solution as the picture now has a little lack of green and the two outputs from the FPGA have been connected together. I hope that this will not kill the FPGA. I think that the resistor will avoid this...

The best solution would be adding the sync signal to green directly on the RGB generator on the FPGA. This will be a minor change and it has no consequence on TVs that are working already.

But it will highly increase the compatibility of ZX-UNO's RGB signal.

P.S.: I don't think that this patch will work on a device where CVBS (video out) is also available on pin 20. In this case I think there will be ghost images or other effekts. In my case white just looks a little bit purple.