archive.worldofdragon.org

Here are the schematics.

I have looked on my Dragon 32 SECAM at the RGB conversion which is part of the PSU board. On my schematics below, we can see that phi A (R-Y) and phi B (B-Y) signals of the 6847 are mixed to make the (G-Y) information. The LUM, which is a clone of (- Y) information is inverted and then combined with...

Hi Stew and John Thank you for your advices. For the moment, I can't reduce the oscillation which causes the vertical lines by putting caps on the power supplies near the 6847 circuit. I will carry on my investigations. My two Dragon RGB have the same behaviour. In RGB output, the vertical lines are...

Thank you Stew for all thoses precious advices, I will look at the power supply. I have taken a picture of the screen with the bars. And also a view of the Y signal given by IC 6847 compared with the Video Clock (oscillo at 0,2 µS per division) When I read the 6847 data sheet, in the case of a 14,21...

My motherboard is like this one. https://archive.worldofdragon.org/images/c/cb/Dragon_32_PCB_Top_%28PN41503_Issue3%29.jpg We can see on the picture that the 8 x OKI M3732H RAMs have the caps. and also that caps have been added, by exemple near the 6809. I don't understand what you mean by "The board...

RGB tests I have tested the RGB on the Scart input of different LCD TVs. It gives a nice picture, but with vertical lines. However, there are 2 things to fix (see schematics for explainations) : - the voltage at pin 16 of the Scart is too low to switch the RGB ; if not corrected, you could only get...

Hello. I have got two Dragon RGB SECAM and I think I'm not the only one here. The motherboard PN 41503 (issue 2 and issue 2A for me) and the SECAM PSU board PN 41504 are already in the hardware section. The quartz frequency is 14,2180 MHz. This machine has two interesting properties : - a RGB circui...