Amstrad GX4000 video sync problem

[saturndual32]

Hi guys.
I just received an Amstrad GX4000 system and the C4CPC cart. I also odered a power supply with the specs 9V, 850ma and center positive. I am trying to display it on a Sony PVM RGB monitor with a SCART cable.

But i am having an issue with the system. When i turn it on, i get a very shaky image and the monitor displays the message: "No Sync". The games run fine, and there are times when the image actually syncs and stays that way for a bit. This is more often on static screens.

I have most of my retro consoles connected this way and have no issues with any of them. I have also tried with 3 diferent SCART cables, but it makes no diference. I tried with the C4CPC and the Burning Rubber cart.

Any sugestions?

[chinnyhill10]

Hi guys.
I just received an Amstrad GX4000 system and the C4CPC cart. I also odered a power supply with the specs 9V, 850ma and center positive. I am trying to display it on a Sony PVM RGB monitor with a SCART cable.

But i am having an issue with the system. When i turn it on, i get a very shaky image and the monitor displays the message: "No Sync". The games run fine, and there are times when the image actually syncs and stays that way for a bit. This is more often on static screens.

I have most of my retro consoles connected this way and have no issues with any of them. I have also tried with 3 diferent SCART cables, but it makes no diference. I tried with the C4CPC and the Burning Rubber cart.

Any sugestions?

You tried the RGB via the monitor out? IIRC the signal on the SCART goes through an encoder chip whereas the monitor is just plain RGB intended for and Amstrad monitor.


Also your supply says it is good for 850mA but is it actually delivering it? This combined with the fact you have a 9v supply means it's quite likely the chip that deals with the SCART connector is probably struggling to supply the voltages needed.

[saturndual32]

I havent tried the RGB monitor out, since i dont have the cable... first i will take your advice regarding the power supply. I think i have one thats 1250 mA, but wrong polarity. I will just hack the cable to give it a try.
Thanks!

[saturndual32]

I tried with another power supply thats rated 9V and 1250mA and got the same problem. I tried using the original GX4000 power supply with Burning Rubber, but it seems to be dead. Seller didnt mention that when i bought it, but i wasnt going to use it anyway since i also bought the flashcart.
Its funny, because there are moments when the image actually syncs for a while...
I guess i will have to order a RGB monitor out cable and a 5V power supply then.

[saturndual32]

Sorry for bringing back this thread after so long. But i have yet to figure out whats the problem with this GX4000 console. Seems like its a video sync problem. Could this be a french unit, i just read that it outputs sync in a diferent way from other GX4000 systems?

[arkive]

So do you actually have an extra power going into SCART itself?

[gerald]

Sorry for bringing back this thread after so long. But i have yet to figure out whats the problem with this GX4000 console. Seems like its a video sync problem. Could this be a french unit, i just read that it outputs sync in a diferent way from other GX4000 systems?

The French version does not have the RF modulator.
If you have a hole at the right side of the GX4000 back instead of a cinch connector, you're on the French side of the GX4000.

And yes, the main difference between French and other version is that Video Out signal (Scart pin 19) is pure sync signal.
On other version, Video Out is a color composite signal.

These do not have the same amplitude : 1Vpp for the video, 5V for the sync.
There is no dedicated sync on the scart, so your cable is likely using the video out signal.
The question is whether the PVM is able to sync on a composite signal while connected in RGB or not.